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Geography 486/586
Laris F’05
OWENS VALLEY - MAMMOTH LAKES - MONO BASIN FIELD TRIP
FRIDAY, SATURDAY, SUNDAY, SEPTEMBER 30-OCTOBER 2, 2005
DEPARTURE: Friday, Sept. 30. Departure from your residence must occur so that sufficient driving time
will yield a 7 A.M. arrival at our first stop at the Lamont Odett Vista Point Parking Area on Highway #14
(Antelope Valley Freeway). The Lamont Odett Vista Point overlooks the Palmdale Reservoir and city of
Palmdale. Driving time from CSULB to the Lamont Odett Vista Point is about 1.5 hours (90-100 minutes). The
Lamont Odett Vista Point is our rendezvous location. You can't be late! If you are late and the class has departed
(we won’t depart prior to 7 AM) continue on to Palmdale Blvd., exit, turn right and find the class past Division Street on
the left at the McDonalds where we have stopped for gas, bathrooms and refreshment. Our next stop is on Highway #14,
about 4.1 miles north of the town of Mohave. Our cars will be parked along the side of the highway.
RETURN: Depart Mammoth Lakes early Sunday afternoon (about 6.5 hours to Long Beach without stops).
ACCOMMODATIONS: Sierra Nevada Aquatic Research Laboratory (SNARL). 1016 Mt. Morrison Road.
Mammoth Lakes California 93546. SNARL is a research center run by UCSB located just off of 395, not far
from the Mammoth Air port. Mattresses are provided. Bring your own a warm sleeping bag or sheets and
blankets and towels. The main lodge has showers, bathrooms, kitchen, cooking and eating utensils, etc. Cost of
accommodations for students is paid for by the Geography Department. Cell phone service is sketchy, the phone
number at SNARL is 760-935-4334 and the director’s name is Daniel Dawson.
MEALS: There will be a group commons table beginning with Friday night dinner and concluding with Sunday
lunch. Cost of the commons table for these six meals will be paid for by the Geography Department. The food
will be simple and will include two breakfasts, two lunches and two dinners. Juice at breakfast, milk, coffee, tea
and hot chocolate are the beverages provided. Preferred other beverages and specialty foods must be provided at
your own expense. Alternatives include eating out at local eateries or preparing your meals individually.
Cooking facilities at the lodge are limited and first priority goes to the commons table.
TRANSPORTATION: Car pool arrangements should be made with members of the Field Class. Cars should
be in good shape and with a full tank of gas when ready to depart Friday morning.
MATERIALS TO BRING:
1. Good walking shoes or boots and warm jacket.
2. Hat, gloves (if cold), umbrella and flashlight could be useful.
3. Towel and bathing suit---the Mammoth Hot Creek will be delightful and a welcome change.
Don't miss this experience.
4. Warm sleeping bag and pillow slip or linens and blankets.
5. Snacks. Friday's lunch to be eaten en-route. Sack lunch is optional.
6. Personal toiletries.
7. Course materials that apply to this field trip.
8. Insect repellent
9. Digital camera
RECREATION: Days are work periods. Evenings are time to relax. Geography 486 students must be in good
shape for the following days' activities --- hangovers not recommended.
GEOGRAPHY 486: FIELD METHODS IN LANDSCAPE ANALYSIS
OWENS VALLEY-MAMMOTH LAKES-MONO BASIN FIELD TRIP
TENTATIVE ITINERARY AND STOPPING LOCATIONS
FRIDAY -- SEPTEMBER 30, 2005 (departure at a time equivalent to 5:30 A.M. from CSULB)
1. Lamont Odett Vista Point for overlook of Antelope Valley and San Andreas Fault (after Pear Blossom Exit from
#14). After Vista Point stop, travel to Palmdale Blvd., exit, turn right to McDonalds (for gas, food and bathrooms).
2. Antelope Valley-about 4.1 miles from junction #14 & #58 at northern edge of Town of Mohave--Desert Flora Study
Site at 2,800’-2,900’. Town of Mohave is 2,760’ and receives 5” - 10” of precipitation.
3. Red Rock Canyon (OPTIONAL)
4. Red Cinder Mountain (Red Hill) and Fossil Falls (north of Little Lake)
5. Olancha-Cartago (3,649’) and Owens Lake. Lunch Break, meet with Ted Scahde of the Owen’s Lake Air
Polluntion Control. (View of Olancha Peak (12,120’).
6. Tour of Owens dry lake bed.
7. Lone Pine (3,700'); (ALTERNATE Lunch Stop at City Park); (view of Mt. Whitney 14,494'
8. Los Angeles Aqueduct at Moffat Ranch Road (just north of Alabama Hills)
9. Manzanar (OPTIONAL)
10. Independence (3,925') and Eastern California Museum (if still open).
11. Owens River Bridge crossing at foot of Westgard Pass.
12. Bishop (4,140'); assemble in City Park on east side of Highway #395
13. SNARL Research Center See directions below
SATURDAY – OCTOBER 1, 2005
Morning
SNARL: Desert flora sampling; 8:15 AM.
Elevation: __________
Mammoth Visitor Center Ranger Station of Inyo National Forest (7,800')
Inyo Craters and Flora Study (8,040’ parking area; 8,202' at lower crater rim)
Oh Ridge Vista Point and June Lake (7,650') - Glaciation
Panum Crater, Mono Craters, Sierra Nevada Vista Point and Flora Observation (6,850')
Mono Lake, Tufa Towers and Flora Observation (6,377' at lake surface) LUNCH
Afternoon
Vertical Zonation of Flora:
Minaret Vista Trail (9,265') on San Joaquin Ridge (drainage divide between Owens and San Joaquin
river systems) and view of Mammoth Mountain summit (11,053')
Long Valley site for viewing moraines of Convict Lake and sampling of flora (7,200’)
Convict Lake (7580'); View Mt. Laurel (11,817’) and Mt. Morrison (12,348’). Glaciation (if Time).
Mammoth Hot Creek (7,217'); 5”-12” of precipitation (much as snow) at parking lot site.
SUNDAY – OCTOBER 2, 2005
Morning
Lake Barret and T.J. Lake. Elevation: __________. Flora Observation and climate change discussion
Afternoon
Eat, Clean-up and Departure for home by 1:00
Sierra Nevada Aquatic Research Laboratory
Director - Daniel R Dawson
HCR 79, Box 198
1016 Mt. Morrison Road
Mammoth Lakes California 93546
Directions
TO SNARL FROM THE NORTH
Take US 395 south toward Mammoth Lakes and Bishop, CA. Do not take the Mammoth Lakes turnoff (Highway 203) off 395.
As you pass the Mammoth turnoff note the reading on your odometer. Proceed another 5.5 miles and you will see a small
green church on the left side of the highway. Stay on 395 one-half (0.5) mile past the church and turn RIGHT
on Mt. Morrison Rd. Proceed to the end of Mt. Morrison Rd. (ca. 1 mile) and you will be at SNARL.
TO SNARL FROM THE SOUTH
Take US 395 north to Bishop, CA. As you head north out of Bishop look for a Shell gas station at the junction of US 395 and
Highway 6. Note the reading on your odometer and proceed north on 395. At 31.3 miles you will pass a turnoff signed
"Crowley Lake Drive/Long Valley". The turn to SNARL, Mt. Morrison Rd., is the next turn on the LEFT, at 32.5 miles.
Proceed to the end of Mt. Morrison Rd. (ca. 1 mile) and you will be at SNARL.
Distances from Bishop to SNARL:
Shell Gas at Hwy 6 0.0 mi.
Out of Town Vons 1.4 mi.
Barlow signal 1.5 mi.
Crowley Lake Drive/Long Valley 31.3 mi.
Mt. Morrison Road 32.5 mi.
Geography 486/586
Laris f2005
FIELD METHODS IN LANDSCAPE ANALYSIS
OWENS VALLEY - MAMMOTH LAKES - MONO BASIN FIELD WORK PROBLEMS
The following hypotheses and exercise will serve as the vehicles for investigation and analysis of the Owens
Valley - Mammoth Lakes - Mono Basin areas. Students are to respond by offering evidence to support or refute
each individual hypothesis (10 points each).
USEFUL GUIDELINES: Be thorough, complete, and don't ignore relevant information. Defining terms and
explaining process are important and necessary elements in responses to hypotheses, particularly the hypotheses
that require consideration of landforms. Diagrams or other figures and photos may be included to enhance the
ability of the reader to understand the content of the response to the hypotheses. Remember, sites of evidence
that support your argument must be identified on a map so that any reader of your discussion could find and visit
the same locations that yielded the evidence you cite.
HYPOTHESES
Note: Questions 1 and 2 are group efforts, questions 3-6 are individual assignments.
1. The flora of the arid Antelope Valley differs significantly in species composition and extent of diversity of
species from the flora of arid Long Valley. In your response to this hypothesis, be sure to identify and explain
the factors that are likely to influence why the composition and extent of diversity of species do or don’t
differ.
2. Flora on the slopes of Mammoth Mountain, the eastern slopes of the Sierra Nevada Mountains and in Long
Valley demonstrate the concept of vertical zonation.
3. The current landscapes of Rose Valley, Owens Valley, Mono Basin and the Mammoth Lakes-Long Valley
area exhibit evidence of the presence of significantly larger volumes of surface water and stream flows in
the recent geologic past (100,000 B. P.). In your response be sure to distinguish between the human and
natural factors that impact these areas. In terms of the latter, you should discuss changes caused by water
diversion projects and the resulting damage to regional atmospheric, ecological and hydrological resources.
4. Mountain glaciation has generated a variety of erosional and depositional landforms in the Sierra Nevada
Mountains and adjacent portions of the Owens Valley, Long Valley/Mammoth Embayment and Mono Basin.
Be sure to distinguish between the two landforms in your response.
5. Extrusive igneous activity has generated a variety of landforms along the eastern flank and adjacent
lowlands of the Sierra Nevada mountains (the adjacent lowlands extend eastward to include the lower slopes
of the uplands that flank the eastern edge of the lowlands).
6. Mono Lake and Owens Lake have similar histories in terms of water diversion and efforts to restore in-flows
and lake levels and to improve lake environments.
LAMONT ODETT VISTA STOP ON HIGHWAY 14 (ANTELOPE VALLEY FREEWAY)
The site of the Lamont Odett Vista Point provides a sweeping view across the Antelope Valley to the
Tehachapi Range portion of the Sierra Nevada Mountains in the far distance. The Antelope Valley is a
triangularly shaped region that constitutes the western-most extension of the Mohave Desert. The Techacapi
Mountains and San Gabriel Mountains, respectively, form the northern and southern boundaries of the Antelope
Valley. Although rocky outcroppings form prominent knobs or hills that rise above the floor of the Antelope
Valley, the valley floor is ringed with very gently sloping alluvial fans built outward from the piedmonts of the
two enclosing mountain ranges. Most of the valley is filled with alluvium to a depth of 1,000-2,000 feet but
locally exceeding 5,000 feet as shown by deep wells. The alluvial fill has been washed down from the
surrounding mountains and has buried the bases of the rocky or hilly outcroppings that appear above the valley
floor. As the south-to-north alignment of Highway #14 crosses the Antelope Valley toward the town of Mohave,
it passes though the Rosamond Hills and past Soledad Mountain and Elephant Butte, three examples of
outcroppings that emerge above the flattish alluvial floor of the valley.
Below the vista site, is the City of Palmdale, the Palmdale Reservoir and the eastern branch of the state built
and operated California Aqueduct on its way eastward through the high desert until it descends through Cajon
Pass and enters the Los Angeles Basin lowlands. The aqueduct terminates in the Lake Mathews Reservoir near
Riverside and brings water to various southern California communities. The water carried by this aqueduct has
come from the western slopes of the Sierra Nevada and Cascade Mountains, particularly from the Feather River
drainage basin. The water in the Palmdale Reservoir is obtained from both ground water sources and the
California Aqueduct.
CLIMATIC AND ECOLOGICAL CHANGE
The Antelope Valley Freeway reaches the Antelope Valley via the route of Soledad Canyon and over Soledad
Pass (3,258’) through the Transverse Ranges before turning north to emerge on the northern piedmont of the San
Gabriel Mountains. The southwest to northeast route through the Soledad Canyon coincides with changing
climatic conditions that become increasingly more arid and characterized by longer and colder winters. Whereas
the Mediterranean climate with its long, hot, dry summers and mild, wet winters is experienced in the San
Fernando Valley, the journey northeastward along Highway #14 traverses a mid-latitude steppe climate where
precipitation decreases northeastward until a true mid-latitude desert climate is encountered on the floor of the
Antelope Valley. Elevations increase along this route before dropping to the floor of the Antelope Valley which
averages about 2,500’-2.600’ feet above sea level. The higher elevations and interior location contribute to the
continental character of the climate in the Antelope Valley. The growing season here is about five months long.
Freezing temperatures are commonplace at night in winter months and snowfall is experienced in some winters.
The climatic change along this route is transitional and reflected in the differing ecosystems that gradually change
from chaparral to steppe to desert as encountered from southwest to northeast. The slopes overlooking the
Lamont Odett Vista Point contain flora encountered in both Chaparral and Desert ecosystems thus reflecting the
transitional climatic conditions experienced at this site.
SAN ANDREAS FAULT
Although not as obvious to the eye, the most significant landform shaping process and feature to be seen at
the Lamont Odett Vista Point is the San Andreas Fault which lies at the northern foot of the San Gabriel
Mountains. The San Andreas Fault is adjacent to the northern edge of the Palmdale Reservoir, and crosses the
Antelope Valley Freeway just at the southern edge of the ridge downslope from the Vista Point. Palmdale
Reservoir lies in a slight depression created by erosion of the soft, ground-up rocks along the San Andreas fault
zone, here about one mile wide. The most recent line of displacement, the break of 1857, lies along the far side
of the reservoir; the displacement was right lateral and locally approached 20 feet. In 1914 the City of Los
Angeles Department of Water and Power (DWP) built the Los Angeles-Owens Valley Aqueduct to bring water
from the eastern slopes of the Sierra Nevada Mountains to the city of Los Angeles. The Los Angeles-Owens
Valley Aqueduct was aligned so that it crosses the San Andreas Fault underground near Elizabeth Lake, 15 miles
northwest of this vista site; the newer California Aqueduct crosses the fault on the surface so that repairs can be
made if damage results from a fault displacement.
Faults are fractures in the earth’s crust along which blocks of rock have slipped past each other. The San
Andreas Fault is not a single strand or fault line, but rather the senior fault (as much as ½ mile or more wide ) in a
large family of more or less parallel faults in a zone as much as 50 miles wide full of fault lines, each the
signature of one or many earthquakes.
In geologic terminology, the San Andreas is a right-lateral fault. The blocks of the earth’s crust, on opposite
sides of the fault, slip past each other horizontally. No matter on which side of the fault one stands, the opposite
side appears to move to the right. Many geologists accept evidence suggesting that total displacement along the
San Andreas Fault in southern California is at least 190 miles with the rocks west of the fault moving north or
northwest. Some geologists think the total movement may amount to as much as 340 miles. The fault separates
the North American and the Pacific tectonic plates of the earth’s crust. If one could stand astride the center of the
fault zone which is the boundary that separates the two tectonic plates, and face north-northwest, the left foot is
on the Pacific plate moving toward Alaska and the right foot is on the North American plate riding backward
toward Mexico.
There are about twenty lithospheric plates that make up the crust of the earth and all are in continual motion.
As the plate movements occur, earthquakes are markers of the incremental steps. 50,000 major earthquakes will
move an object at the earth’s surface about 100 miles. A granite block, originally part of the southern Sierra
Nevada, has traveled three hundred miles along the San Andreas fault system; it is now along the shore at San
Francisco and continues to move northwest. The San Andreas Fault alignment extends southward along the
eastern edge of the Salton trough and beyond beneath the Gulf of California. The peninsula of Baja California is
about to detach and some of what is north of Baja California may go with it.
DESERT SHRUBS OF THE ANTELOPE AND/OR LONG VALLEYS AND MONO BASIN
ADD b/w Photographs!?
1. Bladder Sage (Paper Bag Bush)
Salazaria mexicana
A low shrub two to three feet high; leaves sparse, opposite and appear
naked and twiggy. 4 hard nutlets surrounded by inflated papery
balloons are the calyces that inflate to carry seeds for wind dispersal.
2. Brittle Bush (Incienso)
Encelia farinosa (silvery gray leaves)
Long, upright stems with yellow flowers at tip (dead efflorescence in fall
is rust colored). Aboriginal people burned Brittle Bush as incense to
deodorize dwellings and deter bees.
3. Buckwheat
Eriogonum sp. (67 species known)
4. Burroweed (Bursage, Burrobush)
Ambrosia dumosa (was Franceria dumosa)
Low, rounded, grayish subshrub one to two feet high with divided
very small grayish-green (ashy) leaves and grayish-white bark. A
favored food by burros, sheep and horses. Normally found near and
between Creosote Bush.
5. Checkered Fiddleneck
6. Cheese Bush
7. Creosotebush
Hymenoclea salsola
A shrub with narrow resinous leaves one to two inches long . Is
common in sandy washes and rocky places below 6,000 feet.
(Greasewood)
8. Desert Trumpet
10. Joshua Tree
12. Spiny Hopsage
Larrea tridentata (was Larrea divaricata)
A shrub 2-8 feet high with small green leaves that puts out yellow
flowers in late spring followed by spectacular fuzzy white seed balls .
Creosotebush gives off a musty, resinous odor. Leaves are covered
with a “ varnish” which often glistens in sunlight. Found in
association with Burroweed.
Eriogonum inflatum (inflated stems)
Inflated stems over two feet tall and slender ultimate branches.
9. Hedgehog Cactus (Torch Cactus)
11. Mormon Tea
Amsinckia tessellata
Tan colored stems are covered in horizontally protruding stiff prickly
hairs that give the feel of sandpaper when rubbed by finger. The
curling habit of the opening flower heads resemble the profile of a
fiddle’s neck. The back of the nutlet or seed is tessellate like a
mosaic, or checkered.
Echinocereus engelmann
Yucca brevifolia
(Joint Fir)
Ephedra nevadensis – Gray green stems with seed cones at stem joints
Grayia spinosa
Spine-tipped reddish twigs appear to have loose, whitish, semiparallel strings attached to bark (striped appearance). A fairly
valuable browse plant.
HIGHER ELEVATION SHRUBS OF LONG VALLEY AND MONO BASIN
1. Bitterbrush
Purshia tridentata Dark green, 3 teeth-tipped leaves.
2. Big Sagebrush
Artemesia tridentata Strong sage odor, gray-green 3 teeth-tipped leaves.
3. Greenleaf Manzanita
Arctostaphalus patula
4. Rubber Rabbitbrush
Chrysothamnus nauseosus
5. Sierra Chinquapin
Castanopsis sempervirens
6. Snow Berry
Symphoricarpos acutus Roundish dark green leaves; white berry fruit.
7. Snow Bush (Tobacco Brush)
Ceanothus velutinus
8. Wax Currant
Ribes cereum Light green, grape-like leaves and red berry fruit.
Stiff, green leaves; three veins underside of leaf.
SHRUBS OF ALKALINE SOILS, DRY LAKE BED OF MONO LAKE, ETC.
SALINE SOILS/ALKALI SINK SHRUBS AND HERBACEOUS PLANTS
1. Four-Winged Saltbush
Atriplex canesceus
2. Great Basin Buckwheat
Eriogonum microtheeum
3. Greasewood
Sarcobatus vermiculatus Sarco means “fleshy” (succulent leaves)
White barked, low shrub; numerous, small, bright green, linear,
succulent leaves; roundish to triangular in cross section. Spiny
branches (batus
means “bramble”). Deep tap roots, tolerates
excessive soil salts, is excellent indicator of alkaline soils, .
4. Green Rabbitbrush
Chrysothamnus viscidiflorus
Lacks woolly pubescence, thus appears greener than Rubber
Rabbitbrush. Yellow disk flowers appear in showy clusters.
5. Russian Thistle (Tumbleweed)
Salsola pestifer
6. Saltgrass
Distichlis spicata
7. Seep Weed
Suaeda torreyana
8. Shadscale (Goosefoot)
Atriplex conferfitolia (crowded leaves - atriplex means “not to nourish”)
Old stem tips become sharply pointed. Leaves irregularly shaped.
9. Torrey Saltbush
Atriplex torrey
Ditty to distinguish among sedges, rushes and grasses, “Sedges have edges (triangular in cross section), rushes are
round (in cross section) but grasses are hollow from top to the ground” (with a pithy center).
MOISTURE AVAILABILITY AND CALIFORNIA DESERT SHRUBS
Shrubs in California Dry Lands
The first shrub probably appeared on the earth about 400 million years ago and only remotely resembled most
of the shrubs that exist today. The higher forms of flora can be divided into trees, shrubs and herbaceous plants.
Herbaceous plants lack the ability to produce woody tissue, which distinguishes them from trees and shrubs, and
trees usually have a single main axis or trunk which distinguishes them from shrubs which possess a profusion of
woody stems, many of which spring directly from the ground at the base of the plant.
The most conspicuous and characteristic type of flora in California’s desert and semi-desert landscapes are
shrubs. There are many characteristics shared by California desert, semi-desert and even many chaparral shrubs
that explain how they are able to survive the rigors of heat, cold and aridity so much better than trees. Every
adaptation, however, exacts a price, usually a slower growth rate and/or a lower rate of food manufacture. Most
shrubs, for example, have relatively small leaves which helps reduce water loss, since less surface is exposed to
the dry air. But the price paid is a slower growth rate and a smaller final size. Additionally, the leaves frequently
are leathery or somewhat thick and succulent. Some shrubs have a thick, varnish-like layer on their leaves, the
cuticle, which reduces water loss. Generally, a reduced proportional surface area means a lowered water
transpiration rate, but the price paid is again a slower growth rate.
Classifying Flora by Water Requirements
The need for and availability of water, the range of ambient temperatures, and the seasonal variation in both,
are perhaps, the most important limiting factors that determine the floral assemblage within a region. The water
factor is a dominating consideration when analyzing the physical environment of plants and one strategy for
classifying plants is according to their water requirements, a reflection of the degree to which soil is saturated
with water. The terminology associated with the water requirement factor is derived from three simple Greek
prefix word roots: xero, meaning dry; hygro-(hydro), meaning wet, and meso, meaning intermediate or middle.
Thus a habitat may be prevailingly wet (hygric), dry (xeric) or mesic (an intermediate degree of wetness).
Xerophytes are plants that grow in dry habitats, hygrophytes in wet habitats and mesophytes in the
intermediately wet habitats. Xerophytes are highly tolerant of drought and can survive in habitats which dry
quickly following rapid drainage of precipitation.
Surviving Desert or Xerophytic Conditions
Desert plants (xerophytes) can be grouped into three categories based on the manner in which they have
evolved to survive desert conditions. 1) the drought-escaping plants; 2) the drought-evading plants; 3) the
drought resisting plants.
Drought escaping plants are the “desert quickies,” or ephemerals. Taking advantage of the two seasons of
rainfall on the desert (midsummer showers and midwinter soakers which include in-place snow melt), the
ephemerals develop rapidly, blossom and mature their seeds which lie dormant in the soil during the rest of the
year and thus escape the high season of heat and drought. There are two groups of these quickies that complete a
very short cycle of germination, leafing, flowering, fruiting and seed dispersal; the summer ephemerals, and the
winter ephemerals. The former are hot-weather plants while the later are species that thrive during the cool moist
weather of winter and early spring. These quickies present their spectacular floral displays only following
seasons of above average precipitation.
Drought evading plants meet the heat and drought by reducing the bodily processes to maintain life only.
They drop their leaves, and remain in a state of dormancy until temperature and moisture conditions, suitable to
renewed activity, again prevail. Seeds of many species possess so-called “inhibitors,” bio-chemicals that prevent
germination unless they are thoroughly leached out by more than a passing shower. This means that for many
species, it takes a good soaking rain to get the seed started, one that will wet the ground sufficiently for the
seedling to send a root down below the very surface.
The drought resisting plants survive the drought and heat of the desert through evasive tactics. Cactuses
store moisture in their spongy stem or root tissues during periods of rainfall, using it sparingly during drought.
To reduce moisture loss to a minimum, they have done away with their leaves, the greenskin of their stems taking
over the function of foliage. Other plants develop deep or widespread root systems that extract all the moisture
from a huge soils area. Most drought resisters either cut down their leaf surface to an irreducible minimum
and/or, coat the leaves with a fine-haired texture, wax, or varnish which reduce the rate of evaporation and
moisture loss. Some plants have evolved leaves with whitish surface materials that may reflect light and hence
reduce heat gain, thus restricting the loss of moisture.
Plants, Transpiration and Adaptation to Moisture Deficiencies
Water loss through the leaves is characteristic of all land plants, basically because there is no way to allow the
carbon dioxide necessary for photosynthesis to diffuse into the leaf without losing some water vapor to the air at
the same time. Most leaves are thin, laminar structures and even if they are small, they present relatively more
surface area to the air than would a more compact leafy structure. In conjunction with their growth and life
processes, leaf-bearing plants lose moisture in two ways. They lose most of their water (more than 90%) into the
atmosphere through specialized leaf pores called stomates which in the vast majority of plants are open during the
day and closed at night. The water loss process is termed transpiration; a form of evaporation from water films
upon the exposed surfaces of plant cells (the process is also commonly known as evapo-transpiration).
Stomates must be open during the daytime if the carbon dioxide essential for photosynthesis is to enter the leaf so
that plants may carry on photosynthesis in the presence of sunlight. Photosynthesis can’t occur at night. In
addition to water loss by transpiration, a relatively small amount of water is also required by plants in the process
of photosynthesis to produce carbohydrates. The dominant source of water needed for transpiration and
photosynthesis is from the soil where it is taken up through plant roots.
The rate of transpiration varies greatly according to the type of plant and the prevailing atmospheric
conditions. High temperatures, winds and low humidity favor high rates of transpiration. The plant structure,
particularly of the leaf, largely determines the rate of water loss. Plants with large, total foliage surfaces,
composed of broad, thin leaves, have higher rates of water loss than plants bearing needle leaves, spines, or small
thick leaves. Under conditions of limited water supply but high rates of evaporation, only those plants can
survive that minimize transpiration losses. Some plant adaptations for minimizing moisture loss include
evolution of special leaf structures and small size.
The adaptation of plant structures to water budgets with large water deficiencies is of particular interest
to the plant geographer. As noted earlier, the loss of moisture (transpiration) occurs largely from specialized leaf
pores, called stomata, which are openings in the epidermis (outer cell layer) and cuticle (the very thin,
outermost, protective layer derived from the outer surface of the epidermal cells) through which water vapor and
other gases can pass into and out of the leaf. At least some cooling of a sunlit leaf is the result of transpiration.
Surrounding the openings of the stomata are guard cells which can open and close the openings and thus to some
extent regulate the flow of water vapor and other gases.
Although most of the transpiration occurs through the stomata, some may pass through the cuticle.
This latter form of loss is reduced in some plants by thickening of the outer layers of cells or by the deposition of
wax or wax-like material on or near the leaf surface. Thus many desert plants have thickened cuticle or wax
coated leaves, stems or branches. Frequently this waxy layer is whitish which has the added advantage of
reflecting a significant portion of incoming light which would otherwise add to the heat load of the leaf and
increase transpiration. Apart from the whitish waxy layer, many of the grayish or whitish desert shrubs appear so
because of a layer of fine hairs on the leaf surface. These hairs help reduce water loss by creating a boundary
layer of air with a higher humidity content immediately above the leaf surface which, in turn, presents an obstacle
to water loss and is especially important when the air is moving because even a slight breeze can drastically
increase evaporation. Leaf surfaces that display a layer of fine hairs usually exhibit a woolly-like or velvety-like
texture. Leaves that exhibit a woolly-like texture are said to be “tomentose” while velvety-like textured leaf
surfaces are said to be “pubescent.”
Other stomata related means of reducing transpiration are the development of stomata so deeply
sunken into the leaf surface that outward diffusion of water vapor into dry air is retarded, the restriction in
location of stomata to the shaded under-surfaces of leaves where the leaves curl toward their underside when dry
periods occur. These arrangements help in the same way as hairs to increase the thickness of the stationary air
layer through which water vapor must diffuse and consequently they help slow down transpiration.
A plant may also adapt to a desert environment by greatly reducing the leaf area, or by bearing no
leaves at all. Thus needle-like leaves and spines representing leaves, greatly reduce moisture loss from
transpiration. The spiny hopsage and ephedras such as Mormon Tea have very small or virtually non-existent
leaves. Their green stems contain chlorophyll and carry on the essential photosynthesis. Although the near
leafless character of such plants means a reduction in moisture loss, the reduced surface area for photosynthesis is
a relatively reduced growth rate.
In addition to developing leaf structures that reduce water loss by transpiration, plants in a waterscarce environment may develop strategies for improving their means of obtaining water and of storing it.
Roots become greatly extended to reach soil moisture at increased depth. In cases where roots reach to the
ground water table, a steady supply of water is assured. Plants drawing from such a source are termed
phreatophytes and may be found along dry channels and alluvial valley floors in desert regions. Other desert
plants produce a widespread but shallow root system enabling them to absorb the maximum quantity of water
from sporadic desert downpours which saturate only the upper most soil layer.
Stems of some desert plants are greatly thickened by a spongy tissue in which much water can be
stored. Such plants would be described as succulents of which cacti are common examples. In cacti the foliage
leaf is not present and transpiration is limited to fleshy stems. Moreover, cacti and many other succulents, have
evolved a striking solution to the problem of obtaining enough carbon dioxide while reducing water loss to a bare
minimum. They open their stomates only at night when evaporation is naturally less, and somehow trap the
carbon dioxide which diffuses into the leaf at the same time. The carbon dioxide is trapped during the night
because it combines with an organic acid which in effect stores the gas until daylight. Then the process is
reversed, and the carbon dioxide thus freed can be used in photosynthesis. It will not escape, since the stomates
are closed. Plants with this physiological ability (known as crassulacean acid metabolism) are ideally adapted to
dry habitats since they significantly reduce transpiration by opening the stomates only at night and at the same
time effectively bank carbon dioxide for later use.
The Desert Biochore
All natural vegetation on the land falls into four major structural components or biochores; 1) forest,
2) savanna, 3) grassland and 4) desert. The desert biochore, associated with climates of deficient and uncertain
rainfall or extreme aridity, has thinly dispersed plants and hence a high percentage of bare ground exposed to
direct insolation and to the forces of wind and water erosion or to freeze-thaw action. Although trees are scarce,
the desert biochore may display scattered woody plants (shrubs). Because the desert biochore experiences
climates ranging from extremely hot tropical desert to extremely cold Arctic desert and includes climates with
great seasonal ranges in temperature, a considerable range of biologically limiting factors yield differences in
plant habitats, communities, and associations that occur in the desert biochore.
In general, however, dry desert ecosystems contain widely dispersed xerophytic plants which provide
negligible ground cover. In dry periods, most of the year, the visible vegetation consists mostly of small hard
leafed or spiny shrubs, succulent plants or hard grasses. Many species of small annuals may be present, but
appear only after a rare but heavy rain has saturated the soil. Desert floras differ greatly in species composition
from one part of the world to another.
California Deserts and Key Indicator Species
Geographers, ecologists and botanists have recognized that portions of three different desert types or
regions may be identified in the southeastern portion of California; the Sonoran Desert (Salton Trough and
nearby lower elevation locales), Mohave Desert (Antelope Valley and adjoining Basin and Range lands of
southeastern California including Death Valley, Rose Valley, Inyo Valley and southern part (lower elevations )of
Owens Valley; and the Great Basin Desert centered in Nevada and Utah but extending westward into the higher
elevation basins east of the Sierra Nevada Mountains including Long Valley and Mono Basin in California.
Plants species that grow in profusion in only one of these deserts are known as “indicators” or key
species of that particular desert. In the Mohave and Sonoran Deserts of the southwestern United States, some
plants are often large and in places give a near-woodland appearance. Throughout the Mohave Desert, in the
Antelope Valley and northward in the valleys adjacent to the Sierra Nevada Mountains, the Joshua Tree (Yucca
brevifolia) is a highly visible and dramatic plant with a tall branched woody habit which serves as an indicator
species. Because the presence of this tree yucca marks, more effectively than any other plant, the limits and
extent of the Mojave Desert, this species is worthy of special recognition.
Johsua Tree (Yucca brevifolia)
The Joshua Tree (also called the Tree Yucca) is one of four species of the genus Yucca that grow in
California Deserts. The name Joshua Tree was applied by the Mormons because the plant seemed to be lifting its
arms in supplication as did the biblical Joshua. Requiring an average of 8-10 inches per year, the Joshua Tree is
distinctive because of its short, overlapping harsh leaves growing in dense bunches or clusters and because it
possesses a definite trunk with numerous branches forming a crown. It can attain a height of forty or more feet
and blooms from March to May. A relative of the Lily, its flowers reveal a lily-like aspect with three outer and
three inner fleshy petal-like segments about two inches long. The flowers of this yucca develop as tight clusters
of greenish-white buds at the ends of the branches, but do not open wide as do the flowers of other yuccas.
Joshua Trees do not bloom every year, the interval apparently being determined by rainfall and temperature.
Underground suckers may be sent out and start new individuals.
Birds, a small lizard, woodrats and several species of insects are closely associated with this plant, making use
of it for food, shelter or nest-building materials. Native Americans made extensive use of the leaves for fibers,
the roots for fibers and soap making and the fruits and seeds for food. Yucca leaf fibers from leaves have long
been used for fabricating rope, matting, sandals, basketry, and even coarse cloth while the smallest roots, which
are red, were also used to make patterns in baskets. Native Americans ate the buds, flowers and emerging flower
stalk; the large, pulpy fruits were eaten raw or roasted and the seeds ground into meal. Roots of the Joshua Tree
have saponifying properties and were gathered by some Native Americans for use as soap, especially for washing
the hair.
Co-Dominant Shrubs of the Antelope Valley
Also common are the co-dominants, the Creosote Bush (Larrea divaricata [formerly tridentata]) and
Burroweed, also known as Burrobush and/or Bursage, (Ambrosia dumosa formerly Franceria dumosa),
which usually grow in association with each other up to 3,000 feet. They are the most common species of the
Mohave Desert but their range extends far southward into the lower elevation deserts, are considered to be part of
the Sonoran Desert community, and thus are less truly indicator species.
Creosote Bush (Larrea tridentata) or in past years, (Larrea divericata)
The creosote bush is the most dominant and widespread shrub of the southwestern deserts and is the
characteristic dominant or co-dominant (with Burroweed) on valley bottoms, plains, and alluvial fans, often in
sandy or gravelly poorly developed soils. This species dispersed from southeast to northwest reaching its
northern most extent in the Mohave Desert and Antelope Valley about 5400 BP. Sometimes called Greasewood,
the shrub is almost always rather scattered since its roots spread out to some distance not far below the surface of
the soil where they can absorb what moisture is available after rains. Aromatic, and ranging from 1.5 to over 11
feet tall, this shrub has many slender stems arising vertically or obliquely from the root crown. Lanceolote or
falcate leaves are formed of two glabrous (hairless and smooth surfaced) leaflets fused at the base.
Although creosote bush is more cold tolerant than many Sonoran and Mohave Desert plants, it is
susceptible to extreme freezing conditions, and winter cold determines its northern limit. In the Mohave
Desert the ponding of cold air during winter nights apparently excludes creosote bush from closed basins with
temperatures of -28.o F. representing the lethal threshold. Excessive rainfall, rather than cold temperatures,
apparently determines the upper elevation limits in the Mohave Desert where seed germinability is severely
reduced when rainfall levels between mid-November and late March exceed 6-7 inches. High levels of rainfall
lessen flower production and this factor may also limit upslope movement of the plants. Stems elongate between
February and November with the most rapid growth in July and August in response to rains. Creosote bush is
drought deciduous but it is rare to see a shrub completely lacking leaves.
Creosote bush is extremely resistant to high temperatures. The stem and foliage architecture minimizes
self-shading when conditions for photosynthesis are most favorable and may also improve water use efficiency.
The leaflets may fold together during periods of moisture stress and may also alter their angle to minimize direct
solar radiation. Creosote bush roots secrete biochemical inhibitors that discourage other shrubs (except
Burroweed) from becoming established in close proximity to compete for soil moisture and nutrients.
Although flowers appear at any season following adequate rain, creosote bush usually burst into full
flower with yellow blossoms in April or May, to be followed in a short time by the equally spectacular fuzzy
white seed balls making the shrubs appear to be covered with a light frosting of snow. A rain trigger of at least
0.5 inch is required for flowering. After a rain, the plants give off a musty, resinous odor which is the basis of the
Mexican name ‘little stinker’ for this plant. Its yellow flower petals are twisted a bit and remind one of a
windmill.
Lac, a resinous substance, occurs as an incrustation on the branches and leaves of the creosote bush
thus covering the branch and leaf surfaces with a resinous ‘varnish’ which often glistens in the sunlight and helps
reduce evaporative moisture loss. Because of its strong flavor and resinous sap, it is not browsed on as much as
are many desert shrubs. Compounds in the foliage may repel leaf-chewing insects by acting upon their proteindigesting systems and herbivores are apparently deterred by the toxicity rather than indigestibility of leaves.
Some Native Americans made adhesives and sealant from the lac or resinous substance on stems for use in
mending pottery, making mosaics and fixing arrow points. Dried leaves and flowers were used to treat skin
abrasions and liver ailments. Chemists believe that the resins also have potential as agricultural fungicides,
cellulose stabilizers, adhesives and antioxidants.
Burroweed or Bursage (Ambrosia dumosa) Formerly known as (Franceria dumosa)
Noticeable because of its ashy foliage, burroweed is a low, rounded, grayish or whitish barked shrub
one to two feet high having divided leaves. The stem tips bear the heads of flowers which are small without
petals and the bur-like female heads with sharp spines often persist for a long time. Colorless, the flowers are
wind pollinated and do not need to attract insects. It is one of the most common plants of the desert, often
growing in-between creosote bushes at elevations below 3,500 feet. It flowers from February to June and
September to November. Burroweed is one of the favorite foods of burros, sheep and horses.
Further north and at higher elevation in the Long Valley Caldera and Mono Basin portions of the Great Basin
Desert, the floral composition is typical of the Great Basin Sage association where Great Basin Sagebrush
(Artemisia tridentata) and Bitterbrush (Purshia tridentata) are the dominant shrubs. Also fairly common is
Rubber Rabbitbrush (Chrysothamnus nauseosus). Great Basin Sagebrush, highly aromatic, is an indicator plant
for the Great Basin Desert and is uncommon below 6000’.
Big Sagebrush (Artemisia tridentata)
Probably no other plant is so evocative of the Great Basin as big sagebrush, which according to one
estimate is the most abundant shrub in North America. The genus name for sagebrush comes from one of
two related sources. It may be that the name honors Artemisia, wife of Mausolus, ancient ruler of Caria (in Asia
Minor). Mausolus died in 353 B.C. and his bereaved wife perpetuated his memory by erecting a magnificent
mausoleum which became one of the seven wonders of the world. Artemisia was named in honor of Artemis, the
Greek goddess, Apollo’s sister and Zeus’ daughter who was the virgin huntress or goddess of wild nature. The
genus name may honor Artemis, the goddess, who was reported by a Greek philosopher of the second century to
have delivered a medicinal plant to Chiron the Centaur who named it artemisia. The species name tridentata is
the Latin term for three-toothed, in reference to the three-lobed leaves displayed by the big sagebrush species.
There are over a hundred species of Artemesia distributed throughout the northern hemisphere and into South
America of which nine woody species occur in or very near the Great Basin. Many Artemisia species are not
woody, but the woody forms which exist, constitute an important and conspicuous portion of the flora of the
Great Basin. Of the various species of sagebrush, big sagebrush is best adapted to a wide variety of habitats.
Although some botanists argue that big sagebrush is not really a desert plant but is typically found in steppe or
semi-arid settings with rainfall of about 7 to almost 16 inches per year, big sagebrush is still considered by many
botanists to be a xerophyte.
In many of the desert and steppe shrub associations, there are relatively few young plants or none at all.
Sometimes this is because it takes an unusual event, such as a range fire, to get the seedlings started but their
absence may indicate instead that the individual shrubs in the community are fairly long-lived. Researchers in the
early 1960s concluded that, depending on the site studied, the average age of the oldest big sagebrush varied from
27 to 100 years and the oldest plant observed was 120, as was determined by counting the annual rings of spring
and summer wood in the main stem. Within California’s Great Basin region, big sagebrush commonly grows in
association with rabbitbrush, green ephedra, spiny hopsage and bitterbrush.
Under the best conditions, big sagebrush may reach a height of 8 feet and have stem diameters of over
4.5 inches. Big sagebrush over a meter tall is considered a good indicator of arable land for it prefers deep,
moderately basic soils. A cross section of an older stem will show that the rings of wood laid down each year are
not of uniform width around the center of the stem. It is this characteristic growth pattern that gives rise to the
notable eccentricity of sagebrush stems, with their twisting, tortuous appearance.
One of the striking and unique features of the internal anatomy of the big sagebrush stem is the
presence of a cork layer beneath each annual ring of woody tissue. In most other woody plants, when cork
forms, it develops only outside the woody and food-conducting tissues and composes the outer-most layer of the
bark. Characteristically, when fully mature, cork is impervious to water and also to gases. Although sagebrush,
also has cork in its bark, additional cork is developed within the woody, water-conducting tissues. Each year, as
the growing season begins, a layer of cork is initiated which lies between the new wood ring and that of the
previous year. By early August, the cork layer is two or three cells thick, fully formed and the wood enclosed by
it no longer contains any living cells. Consequently, only the most recently formed annual ring of wood remains
capable of transporting water to the upper part of the plant. The cork layers within the wood protect sagebrush
from excessive drying while also serving to restrict water transport to a relatively narrow zone of wood, compared
to other woody plants where at least several outer annual rings of wood are functional in water transport.
The leaves of big sagebrush are quite variable, in both size and shape. In general they are about 2-3
centimeters long and about 2/3 of a centimeter wide, in the shape of a wedge attached at the narrow end to the
stem. Some leaves, however, may be as long as 6 centimeters and well over 1 centimeter wide. Typically they
have three shallow lobes at the tip. Leaf size and the amount of lobing are good indications of the available
moisture at the times the leaves were forming (if formed during the moist spring they will be larger and have
more lobes than if formed later in the year.
Flowering in big sagebrush occurs from August until well into October and may be stopped only by the
onset of cold weather. After pollination and fertilization, each flower produces a single usually reddish brown
seed enclosed in a woody coat, similar in structure to a sunflower “seed” with its hull, only very much smaller.
Although seeds vary in size they average a little over a millimeter long. Because the yellowish hull encloses air,
the seed will float on water, which may explain why big sagebrush is so common along watercourses in the
desert. The small size of the seeds also favors their being transported in the fur of domesticated and wild animals.
As is true of most small-seeded plants, big sagebrush produces a prodigious quantity of seeds. An average big
sagebrush with a 3.5 foot diameter crown produces at least 350,000 seeds and really vigorous individuals in a
good year may produce over a million seeds. Such prodigiousness helps to explain why big sagebrush is such a
widespread and successful shrub. Dispersal of the seeds begins in October and sometimes into January. Quite
often, desert plant are characterized by producing seeds which fail to germinate unless they are exposed to cold,
have their tough coat scratched open, or undergo some kind of after-ripening period. This does not appear to be
the case with big sagebrush, however. Usually its seed will germinate immediately after burial, although some
exposure to cold does appear to improve the germination percentage. Once germinated, the seedlings grow
rapidly under good conditions, and may begin to flower within four years.
Sagebrush has a stout taproot which grows to a depth of between 3 and 13 feet and frequently
penetrates to the capillary zone just above the water table. Its deep root system is one of its most effective
devices for coping with a severe water shortage. In addition, many radially spreading lateral roots near the soil’s
surface insure that the moisture from a light rainfall will also be readily absorbed. The leaves at all stages of
development are surfaced with a dense layer of short hairs, which are dead and hollow at maturity. These hairs
reflect some of the light and are responsible, along with the chlorophyll in the leaves’ interior, for their greenish
gray, silvery appearance. In addition to the dead hairs that help retard water loss, big sagebrush leaves also have
living hairs that are glandular in nature and secrete the characteristic ethereal oils, some of which account for this
shrub’s unique sage/mint-like odor. It is possible that the abundant production of volatile oils which blanket the
surface of the leaf may be effective in reducing water loss.
One of the natural processes that big sagebrush does not appear to be well adapted to is fire. It seldom
root-sprouts after a fire, depending primarily on seeds buried in the soil or carried in by animals to re-colonize a
burnt area. However, since the seedlings compete poorly with grasses, re-establishment is frequently delayed
indefinitely.
Although livestock benefit only slightly from big sagebrush, the shrub is of considerable importance to
wildlife, and, historically, was significant as a medicinal and food resource to Native Americans and as a
source of fuel to early settlers. A tea made from its leaves was considered effective as a tonic, as an antiseptic
for wounds, as a remedy for colds, sore eyes, and diarrhea, and as a way of warding off ticks. One of its more
unusual uses was as a hair tonic. Native Americans also utilized the seeds for food as they pounded them into
meal or ate them raw. Settlers discovered that the wood of the shrub ignited easily, burned with an intense heat
and was utilized in mine smelters.
Although cattle find big sagebrush unpalatable, sheep and goats find it edible, especially in winter when
little else may be available. The leafy tissue of this species of sagebrush contains terpinoids, biochemical
compounds of the monocyclic hydrocarbon class which are unpalatable to cattle. as a browse. Certain other
sagebrush species which are more palatable to cattle have a lower concentration and a reduced variety of these
terpinoids. If it were not for these protective compounds, there would undoubtedly be much less sagebrush in the
Great Basin for its leaves equal alfalfa meal in protein content and have more carbohydrates and twelve times
more fat. Big sagebrush leaves and flowers constitute most of the diet of the sage grouse and are also a primary
food source for antelope, elk and deer. Studies reveal that deer apparently avoid the influence of the volatile
compounds in sagebrush by “belching” them as they chew their cuds. Although the shrub furnishes only a minor
percentage of the diet for such animals as jackrabbits and ground squirrels, big sagebrush is invaluable in
providing needed cover for a host of desert animals.
Bitterbrush (Pursia tridentata)
Almost as apparent a part of the Great Basin flora as sagebrush, is bitterbrush, Purshia tridentata
(often known as deerbrush or deerweed). The genus name Pursia honors Frederick Pursh, an early American
botanist who published studies of western American flora in the early 19th century. As is true for big sagebrush,
the species name tridentata is the Latin term for three-toothed, in reference to the three-lobed leaves displayed by
bitterbrush. Bitterbrush usually varies between three and six meters in height although in favorable locations
heights of nearly ten feet may be attained. Flowers borne on the stems at the base of the leaf clusters bloom from
early spring to July, depending on the elevation. Most of the leaves are lost with the onset of winter. Like
sagebrush, bitterbrush is one of the most ubiquitous shrubs of the Great Basin and can be found in an enormous
variety of habitats ranging from arid flats, provided they are not saline or extremely dry, to alpine zones well
above timberline. In favorable locations bitterbrush will grow to be almost ten feet tall while above timberline it
hugs the ground. Bitterbrush roots penetrate to greater depths than those of sagebrush and allow bitterbrush to
absorb water from deeper zones within the soil even though adjacent sagebrush plants may show water stress as a
result of their shallower root system.
Bitterbrush is a pioneer shrub at seemingly hostile sites although it will not grow on calcareous or
saline soils. Following fires, bitterbrush may resprout from the roots, depending on the amount of soil moisture
available. Bitterbrush on pumice soils appears to make the fastest recovery after fire and pumice appears to be a
particularly supportive medium for the growth of this species. The most ancient bitterbrush individual known, at
least 162 years old, was located in the early 1960’s on the pumice soils of the rim of Panum Crater in Mono
Basin.
While Native Americans historically exploited bitterbrush as a source of medications, the shrub is
currently revered a great deal more than sagebrush because of its palatability for livestock and wildlife.
Great Basin Native Americans made extensive use of bitterbrush as a remedy for chicken pox, smallpox, measles
and venereal disease. A solution prepared from the leaves was thought to be a good antiseptic for rashes,
scratches and insect bites. Tea prepared from the leaves or bark was believed to be useful against tuberculosis,
pneumonia and colds. Currently, bitterbrush has considerable importance as a browse plant for wildlife and
livestock. Sheep, especially, tend to eat the young plants and buds while cattle graze on the more mature plants.
Deer can exist for months feeding only on bitterbrush while antelope, elk, and big horn sheep utilize bitterbrush
extensively. Even the seed forms a significant part of the diet of some birds and other small animals; rodents and
ants collect virtually the entire bitterbrush seed crop when it falls to the ground.
Rubber Rabbitbrush (Chrysothamnus nauseous)
There are some twenty subspecies of rubber rabbitbrush, most of which have a strong characteristic
odor, especially apparent when the twigs are broken. The genus name comes from two Greek words, chrysos
meaning gold and thamnos meaning shrub. The species name, nauseous, refers to the strong odor emitted by the
plant. Rabbitbrush is typically a plant of waste areas, abandoned farmsteads, fence rows, highway shoulders and
disturbed sites in general. Indeed, rabbitbrush is one of the first shrubs to invade a disturbed area and it resprouts
so readily after a fire that former sagebrush and bitterbrush communities will, within a short time after a fire,
appear to be pure rabbitbrush stands.
Humans, livestock and wildlife have all found some benefit from this species. Native Americans of the
Great Basin, not only were accustomed to chewing the stems of rabbitbrush in order to extract the latex in the
belief that chewing the rabbitbrush gum relieved both hunger and thirst, they also thought that a tea prepared from
the shrub was good for colds and stomach problems; some individuals, however, show an extreme allergic
reaction to rabbitbrush. Although rubber rabbitbrush produces a high-quality rubber, called chrysil, which
vulcanizes easily, the total amount of rubber in all the wild rabbitbrush plants in the western USA wouldn’t
amount to enough to make the effort of extracting it economically worthwhile. Rabbitbrush is of little value to
cattle but the flowers and seasonal leaves in late fall and winter are eaten by sheep, goats, and antelope. Deer
make some use of this shrub during the winter.
Halophytes
In many desert biochore settings, the pedogenic (soil producing) process of salinization, or evaporation
of lake waters, may produce local areas of salt crust where halophytes (salt-loving or salt-tolerant plants)
can survive. In the saline playas that exist in many California desert basin bottoms (the sites of former lakes and
now dry lake beds), relatively few plants have evolved a solution to the problem of too much salt in the soil.
Much of the problem with saline soils appears, on the basis of recent research, to be the result of the toxicity of
various common elements and the way in which they interfere with normal physiological processes in plants.
Even those mineral elements essential to plant growth are toxic at high concentrations which is often the case in
saline playas. Some halophytes have developed specialized cellular mechanisms which apparently have the
ability to keep certain toxic elements from accumulating to high levels within the plant.
Such soils and species may be observed on the floor of the Mono Basin, part of which is now exposed as
a dry lake bed by the retreat of Mono Lake’s shoreline over the past almost six decades. Various species of
the genus Atriplex are common shrubs and key indicators of saline soils in such basins. Common to these
conditions in Mono and Long Valley Basins are Shadscale (Atriplex confertifolia), Four-Winged Saltbush
(Atriplex canescens), Torrey Saltbush (Atriplex torreyi), Spiny Hopsage (Grayia spinosa), Russian Thistle
[Tumbleweed] (Salsola pestifer), Saltgrass (Distichlis spicata) and Seep Weed (Suaeda torreyana) and Green Molly
(Kochia americana).
Ditty to distinguish among sedges, rushes and grasses, “Sedges have edges (triangular in cross section) and rushes are
round (interiors are solid), while grasses are hollow from top to the ground (may have a pithy, loose tissue in the interior).”
Bibliography
Dodge, Natt N. and Jeanne R. Janish. Flowers of the Southwest Deserts. Southwest Parks and Monuments
Association: Tuscon. 1985.
Mozingo, Hugh. Shrubs of the Great Basin: A Natural History.
Vegas:1987.
University of Nevada Press; Reno: Las
Munz, Philip A. California Desert Wildflowers. University of California Press: Berkeley. 1962.
Taylor, Ronald J. Sagebrush Country: A Wildflower Sanctuary.
Missoula, Montana: 1992.
Mountain Press Publishing Company.
Turner, Raymond M., Janice E. Bowers and Tony L,. Burgess. Sonoran Desert Plants: An Ecological Atlas.
University of Arizona Press. Tucson. 1995.
GLOSSARY
Angiosperm [Greek. angion: vessel and sperma (meaning seed)]. One of the flowering plants; literally, one
whose seed is carried in a “vessel” (the vessel is the fruit).
Annual A plant that completes its life cycle in one growing season (usually less than one year).
Biennial Referring to a plant whose life cycle includes vegetative growth in the first year and flowering and
senescence (death) in the second year. Contrast with annual and perennial.
Biochore Term introduced by Pierre Dansereau in his 1957 publication, Biogeography. The biochore is the
geographical environment where certain dominant life-forms appear to be adapted to a particular conjunction
of meteorological factors; each biochore is characterized by a major type of vegetation; within each biochore
there develops one or more formations and within each of these formations, climax areas can be
distinguished. Not all the space is taken up by climax vegetation, for the nature of the topography will
allow a differentiation into many habitats. A habitat may harbor one or more ecosystems which may
themselves be comprised of one or more communities.
Biomass The amount or volume of living material (weight of living plant and animal tissue) per unit of land
area.
Biome A biome is the largest terrestrial ecosystem convenient to recognize.
Climax Stage The final seral phase in a sere.
Conifer [Greek konos: cone plus phero: carry]. One of the cone-bearing gymnosperms, mostly trees such as
pines and firs.
Cuticle [Latin. From cuticul meaning the skin]. A very thin hyaline (horny and somewhat transparent) film
covering the surface of plants, derived from the outer surface of the epidermal cells.
Dicot (short for dicoltyledon) [dis: two plus kotyledon: a cup-shaped hollow]. Any member of the angiosperm
class Dicotyledonae, flowering plants in which the embryo produces two cotyledons prior to germination.
Leaves of most dicots have major veins arranged in a branched pattern.
Ecology The word ecology was coined in 1869 by Ernst Haeckle by joining the Greek words oikos, meaning
dwelling place, and logos, meaning "study of." The study of ecology means examining how plants and
animals and their non-living (physical) environment interact and influence each other.
Ecosystem A term introduced in the 1930s which became popular in the 1960s. An ecosystem is a functioning
(interactive and dynamic) assemblage of the biological community (plants and animals), soils, water, humans,
meteorological factors and time, of whatever size.
Ephemeral [Greek. ephemeros: short lived]. A short lived plant or plant that proceeds
life
cycle.
quickly through its
Epidermis [Greek. epi: on, over, upper skin plus derma: skin]. A thin layer of cells forming the outer layer or
skin of seed plants and ferns.
Fascicled [from fascis, Latin for bundle or packet]. A cluster or tuft of leaves that are bundled together at the
petiole/stipule connection.
Fruit In angiosperms, a ripened and mature ovary (or group of ovaries) containing the seeds. A modified
flower part that encloses a seed or seeds.
Glabrous [Latin. glaber: smooth, hairless]. Leaf texture where the leaf surface and bottom is without hair and
therefore smooth.
Glandular Leaf texture where the leaf is somewhat sticky.
Gymnosperm [Greek. gymnos: naked plus sperma: seed]. A plant, such as a pine or other conifer, whose
seeds do not develop within an ovary (hence the seeds are “naked”).
Halophyte [Greek. hals: salt plus phyt(on): meaning plant]. A plant which grows in salty or alkaline soil.
Herbaceous Plant An annual plant that is non-woody.
Hygrophyte [Greek. hygros: wet or moist: plus phyt(on): meaning plant]. A plant that thrives in wet or very
moist ground.
Lobed Leaf margin having lobes or divisions extending less than halfway to the middle of the base or midrib.
Mesophyte [Greek. mesos: middle plus plus phyt(on): meaning plant]. A plant growing under conditions of
well balanced moisture supply.
Monocot (short for monocotyledon) [Greek monos: one plus kotyledon: a cup shaped hollow]. Any member
of the angiosperm class Monocotyledonae, plants in which the embryo produces but a single cotyledon (seed
leaf). Leaves of most monocots have their major veins arranged parallel to each other.
Nectar In flowers, a nourishing solution of sugars and amino acids.
Pedogenic [Greek. pedo: soil plus genic: stem ending meaning “producing or arising from”]. Soil producing.
Perrenial plant that has a life cycle of more than two years.
Phloem [Greek. phloos: bark]. In vascular plants the specialized food conducting tissue in the vascular
system that transports dissolved sugars.
Photosynthesis [Greek. Literally ‘synthesis out of light”]. Metabolic processes, carried out by green plants, by
which visible light is trapped and the energy used to convert the sunlight into the chemical energy of glucose.
Phreatophyte [Greek. Phreat meaning artificial well]. A long rooted plant that absorbs its water from the
water table or the soil above it. “Phreatic” notes or pertains to that layer of soil or rock through which water
may enter wells or from which springs and seeps may emerge.
Pollen [Latin. Fine powder, dust]. The fertilizing element of seed plants, containing the male gametophyte and
the gamete, at the stage in which it is shed. The yellow, powder-like male sex cells on the stamens of a
flower.
Pubescent Leaf texture where the leaf surface possesses many fine, short hairs and an almost velvety feel.
Seed A fertilized , ripened ovule of a gymnosperm or angiosperm. Consists of the embryo, nutritive tissue and
a seed coat.
Scalelike Leaf shape formed by the arrangement of leafs or leaflets in tight scale-like pattern.
Seral Stage(s) The various recognizable phases of succession that characterize the changing ecosystem as the
dynamics and component living organism (plants and animals) evolve toward a "climax" stage (stability or
equilibrium).
Sere The various stages or phases of plant and animal succession that occur in an area following a substantial
alteration to the area’s ecosystem.
Shrub A bushy, woody plant with several permanent stems instead of a single trunk. Shrubs generally are
shorter than trees.
Stipule One of a pair of lateral appendages, often leaf-like, at the base of a leaf petiole in many plants.
Stoma (plural stomata) An aperture (opening) in the epidermis of leaves that regulates the passage of gases
into and out of a plant.
Succulent [Latin. succus: juice plus lentus: a suffix meaning full of]. A plant having fleshy and juicy tissues.
Taproot The organ that results when the primary root grows downward and becomes the largest root.
Taxonomy The science of grouping organism according to their presumed natural relationships.
Tomentose [Latin. tomentum: stuffing of wool or hair for cushions]. Leaf texture where the surface is woolly;
covered by many wavy hairs forming a wool-like texture.
Transpiration [Latin. spirare: to breath]. The evaporation of water from plant leaves through the stomata
and from stems, driven by heat from the sun, and providing the motive force to raise water from the roots.
Vascular Cambium The lateral meristem in a plant that produces additional vascular tissue (wood if the
xylem)
Vascular Plant A plant that has xylem and phloem.
Vascular Tissue The tissue that transports water and food from one part of a plant to another.
Woody Plant A perennial vascular plant containing xylon tissue and adapted for growth year after year, such as
a tree.
Xerophyte (xerophytic) [Greek. xero: dry plus phyto: plant]. A plant adapted for growth under dry
conditions.
Xylem [Greek. xylon: wood] In vascular plants, the woody tissue that transfers water and minerals from the
roots to the leaves.
ROSE VALLEY, RED CINDER MOUNTAIN (RED HILL), FOSSIL FALLS, COSO MOUNTAINS AND
COSO GEOTHERMAL FIELD
Rose Valley
Alluvial fill, extrusive igneous materials comprised mostly of basalt flows and the water bodies of Little Lake
and Haiwee Reservoir are the dominant surface features of the Rose Valley. The depth of the alluvial fill is
unknown but is likely to be quite deep as the Rose Valley floor has been down-dropped while the adjoining Sierra
Nevada and Coso Mountain ranges have been uplifted along the fault lines/zones sited on the western and eastern
edges of the valley. A narrow linear valley formed by the down-dropping of a block of the earth’s crust between
two rising crustal blocks, is known as a graben or rift valley. Rose Valley stretching from a little south of Little
Lake to the latitude of Olancha Peak (12,120’) in the north, can be identified as a rift valley similar to the Owens
Valley further north, although shorter and narrower.
The eastern front of the Sierra Nevada Mountains is higher and steeper at the latitude of Rose Valley
compared to the more southerly reach of the range. The rocks composing the range front are older granitics with
some metamorphic pendants which weather readily so that the slopes are largely debris mantled rather than bare
rock. Just south of the southern entrance to Rose Valley and just south of the Inyo County/Kern County
boundary, the core of the Sierra Nevada Range emerges at Owens Peak (8,475’). Comprised of hard, clean, fresh
granitic rocks with a rugged topographic expression, the Sierra crest steadily increases in elevation northward to
Olancha Peak (12,120’) and then reaches its highest elevation at Mount Whitney (14,495’) at the latitude of Lone
Pine, the second largest town in the Owens Valley.
The Coso Mountains and Extrusive Igneous Activity
Most of the vertical movement associated with the dropping of the Rose Valley floor and raising of the Sierra
Nevada and Coso Ranges occurred over the last few million years and the crustal weakness along the Coso
Mountain flank is reflected in the local presence of igneous materials and landforms within and atop the Coso
mountains and as a blanketing of portions of the Rose Valley floor. The north/south aligned Coso Mountain
Range is partially capped by igneous rocks derived from eruptive activity that began about 4 m.y. B.P. and thirtyeight volcanic domes have been mapped in the Coso Range. The most dramatic of the domes include Volcano
Peak, Glass Mountain, and the Perlite Domes. The volcanic material of the Coso Mountains is underlain by rock
material similar to that of the Sierra Nevada Mountains.
Reflecting more recent extrusive igneous activity are the basaltic flows that originated from vents within and
along the western flanks of the Coso Mountains to course down slope into the Rose Valley where extrusive
igneous features including solidified lava flows with columnar jointing at the face of the flows, rhyolite plugs and
pressure mounds occupy portions of the valley surface. In addition, Red Cinder Mountain, a dramatically
symmetrical cinder cone fed by a conduit of unknown origin, is located in the center of the valley.
Sprawling across the southern end of the valley and extending to the northern edge of the Indian Wells Valley,
are the Lower Little Lake Ranch basalt flows (440,000 B.P.) that originated from Volcano Peak in the Coso
Mountains. Columnar jointing appears along the face of the flow. These basalt flows moved southward and
southwestward during the Pleistocene epoch and deflected the flow of the glacial Owens River. At the southernmost tip of Rose Valley, the erosive power of the Pleistocene age Ancient Owens River was sufficient to carve a
deep channel through the solidified lava which then served as the spillway for the Ancient Owens River as it
departed southward from Rose Valley and emptied into Glacial China Lake which occupied Indian Wells Valley
in Pleistocene times.
Later in the Pleistocene epoch, the Upper Little Lake Ranch basalt flows (140,000 - 90,000 B.P.) spewed
from Volcano Peak to also flow westward and southward atop the Lower Little Lake Ranch flows. The flow
contains a mile-wide zone of basaltic cones and rhyolite plugs that extend along a lineal depression stretching
from Red Cinder Mountain in the north to the vicinity of Airport Lake in the south. In the vicinity of Volcano
Peak, the basalt flow displays small cones and plugs of perlitic rhyolite (volcanic glass appearing as enamel-like
globules) surrounded by lapilli (pyroclasts less than one inch in diameter) from the eruption of the plugs.
The western surface of the Upper Little Lake Ranch basalt flow is dotted with elliptical “pressure mounds.”
Pressure mounds identify sites in the basalt flow where surface lava cooled and solidified more quickly than
deeper molten material which was hotter and more viscous. The more viscous lava continued to flow causing the
overlying hardening and more brittle lava to buckle and mound upwards.
The most recent basalt flow is evident along the western flank of Volcano Peak where a tongue of solidified
lava (38,000 B.P.) extends hundreds of feet downslope from the summit of Volcano Peak. Volcano Peak
(5,350’) is a symmetrical cone of dark basalt.
Red Cinder Mountain (also called Red Hill and Red Hill Cinder Cone; not to be confused with Red
Mountain, another cinder cone located much further north near Big Pine in the Owens Valley) is a partially
breached phreatic cone located in the middle of Rose Valley adjacent to Highway #395. Red Cinder Mountain
dates from 21-22,000 B.P. (although it could be 140,000 - 90,000 B.P. which is the age of underlying basalt
flows). The feature is a phreatic cone, an accumulation of ejecta of cinder size that was blown skyward by the
violent release/escape of vaporized, superheated groundwater beneath the lava flow upon which it stands. The
cinders contain small, lath-shaped crystals of labradorite and augite, and dark brown inclusions of basaltic glass.
The cone of Red Cinder Mountain appears to be but a few tens of thousands years old and some researchers
have dated its formation to about 22,000 B.P. If it is phreatic it should be contemporaneous with the flow upon
which it stands; the Little Lake Ranch Basalt Flow upon which it stands, however, has a potassium-argon date of
140,000 +/- 90,000 years B.P. derived from a sample taken one mile to the south. The cinder cone is mined for
scoria or pumice (vesicular lava where the abundant cavities were formed in the once molten lava as gas bubbles;
the gas subsequently escaped when the lava cooled and solidified) along its southern slope. Light-weight
vesicular scoria has commercial value as roofing granules, forming lightweight concrete bricks and blocks and
making abrasives.
Glacial Owens River and Fossil Falls
In Pleistocene times, the overflow of Glacial Lake Owens spilled southward into Rose Valley to form the
Ancient Owens River which deepened and widened its drainage channel at the foot of the Coso Mountains (the
channel is now mostly occupied by the DWP’s Haiwee Reservoir). As the Ancient Owens River flowed
southward through Rose Valley and encountered the Little Lake Ranch basalt flows, the river, in places, was
forced westward and finally dammed by the solidifying basalt flow about 0.5 mile east of the edge of the basalt
flow.
Here, water accumulated in a shallow lake, now a playa. Eventually, the overspill from the dammed water
etched a new channel 100 feet wide and 6 to 10 feet deep into the surface of the solidified lava flow. Today,
water-carved boulders are strewn about the dry river bed attesting to the volume and power of the Ancient Owens
River and how large were some of the components of its load. Further south, the Ancient Owens River flowing
through its newly carved channel spilled over the edge of the Upper Little Lake Ranch basalt flow to form a
waterfall that plunged more than 100 feet to the channel below at the base of the lava flow. The lava has more
sodium potassium and titanium than is common in basalts.
Great volumes of water (3,500 cubic feet per second) flowed over the falls and on south through the channels
that are currently partly occupied by the Little Lakes to feed and sustain Glacial China Lake and even Glacial
Searles Lake. At the time of maximum filling, Glacial China and Searles Lakes were joined and covered 384
square miles. The last major discharge occurred 10,000 to 15,000 years B.P. while progressively smaller flows
continued until the last overflow of water occurred between 3,500 and 4,000 years ago.
Fossil Falls
The site of the waterfall evolved in subsequent millennia to consist of a cascade occurring in two drops. At
the top of the falls, a narrow canyon three hundred feet long was incised headward into the flat bed of the river.
The canyon reached a depth of 40 feet at its western and deepest point where the gorge widens into a smooth, flatbottomed channel. Below the flat stretch of channel, the canyon floor drops abruptly for about 30 feet. All
through the gorge, the rocks were carved into fantastic shapes by the torrents of swiftly moving and eddying
glacial melt water. Today, large potholes abound to reflect the erosive power of the Ancient Owens River; one
vertical pothole, open at the bottom, is 2 to 3 feet in diameter and 12 feet deep. The carving action of the water is
ascribed to semi-permanent eddies formed during the flow, with erosive effects being due to abrasive action by
suspended silt, sand and rocks. The basalt itself is slightly soluble in warm water. The lava is also traversed by
fractures through which water descended freely where it produced a rotational flow, like water draining from a
sink. Today, the basalt surfaces of the gorge are heavily covered with desert varnish and gleam in the sunlight as
the gorge and site of the ancient falls are dry.
The Ancient Owens River and site of Fossil Falls was an attractive location to aboriginal peoples many
millennia ago. Numerous living sites (middens) and many artifacts including flaked chips of obsidian, some
shaped as arrowheads, were found scattered along the banks of the river channel by researchers. The obsidian
comes from exposures in the Coso Range only a few miles to the northeast.
Little Lake and Haiwee Reservoir
Little Lake, occupying a portion of the channel of Ancient Glacial Owens River, and once called Little Owens
Lake, is nourished by small seepage springs. Now a shallow haven for migratory water birds including ducks and
geese, the early ‘Pinto’ peoples were known to have resided here as, later, did Piute and Shoshone peoples.
About ten miles north of Red Cinder Mountain is the site of the channel of the Ancient Owens River which
lost most of its water about 4,000 years ago. As the local climate became drier, spring water from the Cosos and
Sierra Nevadas along with periodic rain storms sustained small hunting and gathering Native American groups in
the Rose Valley. Seasonal meadows characterized the bed of the Ancient Owens River and before the
construction of the DWP L.A. Aqueduct, this site was known as the Hayway or Haiwee Meadows from the
aboriginal word for dove. In the 1860s the Haiwee Meadows was the centerpiece of a ranch of 10,000 goats.
A gap, carved by the Ancient Owens River in a westward reaching spur of the Coso Range, is the site of a
dam and powerhouse erected by the DWP to receive and store the water delivered by the L.A. Aqueduct from the
Owens Valley. The Haiwee Reservoir, which fills behind the dam, consists of two basins, northern and southern,
and is the final storage location for L.A. Aqueduct water before it enters the two big pipelines that convey the
water to Los Angeles.
LOWER OWENS VALLEY, OWENS RIVER AND OWENS LAKE
LANDFORMS, DIVERSION OF WATER, DESSICATION OF OWENS LAKE AND RESULTING
ENVIRONMENTAL ISSUES
Owens Valley, Lake and River all take their name from Richard Owens of Ohio, a captain in John C.
Fremont’s 1844-45 journey of exploration in the West. Fremont named these features after the Captain in 1846
although Owens did not pass through the Owens Valley and never saw these features named for him.
OWENS VALLEY AS A GRABEN (RIFT VALLEY)
Alluvial fans form the dominant landform features of the Owens Valley and the surface of the alluvial fans
represents the top layer of alluvial fill that extends downward to the hard basement rock of the Owens Valley
floor. The depth of the alluvial fill is extraordinary and has been measured at 6,000’ below sea level (almost
10,000’ of fill) to the east of Lone Pine. The Owens Valley floor has been down-dropped while the Sierra
Nevada and Inyo-White Mountains have been uplifted along the fault zones sited on the western and eastern
edges, respectively, of the valley. A narrow linear valley formed by the down dropping of a block of the earth’s
crust between two rising crustal blocks, is known as a graben or rift valley. All the vertical movement associated
with the dropping of the Owens Valley floor and raising of the Sierra Nevada block occurred over the last few
million years for a total of over 20,000 feet of vertical displacement between the bedrock bottom of Owens Valley
and the crest of the Sierra Nevada. Four to five feet of uplift of the Sierra Nevada block occurred during the 1872
earthquake that was centered near Lone Pine.
The fault lines, as alignments of crustal weakness, are reflected by the presence of the Big Pine Volcanic
Field’s lava flows and cinder cones that were fed by conduits located along the fault lines at the flanks of the
valley Material eroded from the rising blocks of the Sierras and Inyos are the source of the deep alluvial fill of
the valley as well as the coalescing alluvial fans at the surface.
OWENS LAKE: PAST, PRESENT AND PROBLEMS
Location
Owens Lake is located 17 miles south of Lone Pine in the southern reach of the Owens Valley. Extending
across an area of 110 square miles (285 square kilometers), this lake bed, once part of a chain of Pleistocene
lakes, was full of saline water until the 1920s. Owens Lake is the natural sump for all the streams flowing into
Owens Valley. Before the Los Angeles Aqueduct diverted the Owens River, it was a salty shallow lake, thirty
feet deep at its maximum depth. By 1921, it had shrunk to half this size and trona ( a sodium carbonate salt)
began to crystallize on the lake bottom. Now dry, the lake bed reflects chemical and physical processes at work
in a wet, natric (sodium dominated) playa as well as climatic changes and the consequences of human
exploitation of the local desert environment.
Early Landscape History
The chain of Pleistocene freshwater lakes that extended from Mono Lake to Lake Manly in Death Valley, and
included Owens Lake, was full during much of the Pleistocene epoch. Pleistocene epoch shorelines of the Tioga
glacial age, ring the Owens Lake Basin about 300 feet above the lake bottom. In places the ancient shorelines
have been incised by small quebradas (ravines) that have built alluvial fans onto the sloping surface beneath but
are otherwise uneroded. Flow to the south of Owens Lake probably ceased 3,500 to 4,000 years ago.
During the alluvial episodes, rainfall of at least 20 inches per year prevailed over most of the desert. The rain
probably came from the Pacific Ocean to the south, rather than from frontal storms of more northerly origin that
are now prevalent. Under the influence of the present-day semi-permanent high pressure area, a strong diurnal
(24 hours) heating develops. Heated air rises at the sides of the valleys and descends in the central parts, being
reheated by compression during descent. The heating produces a low-level, dry, thermal low pressure that
advects (draws in air horizontally) the surface air from the desert to the south and east, further warming the
region.
A well drilled 920 feet deep in the central part of Owens Lake revealed a continuous series of clays and silts
but no-buried salines (salty substrates). Although researchers argue that the lake had not desiccated (dried out)
for several hundred thousand years, some episodic drying must have occurred because extensive layers of coarser
sediments beneath the clays give rise to artesian wells. The latest desiccation (drying out) of Owens Lake was
initiated by climatic change, accelerated by irrigation and finished by the export of water to Los Angeles.
An Abbreviated Human History of the Owens Valley
The earliest Native American inhabitants of the valley and lake shore area probably arrived after the Tioga
glacial epoch (after 18,000 BP). Although various aboriginal groups occupied the valley over thousands of years,
their numbers were small, their density sparse, none practiced agriculture and none had much impact on the
environment of the valley. The first Spanish and American travelers to visit the Owens Valley described the
aboriginal inhabitants as subsistence hunting, fishing and gathering peoples.
In 1862, American farmers began to settle the Owens Valley as they found water resources for irrigation to be
abundant. By 1917, 62,000 acres were in cultivation, 160,000 fruit trees had been planted and 450,000 acre feet
of water were being used annually, mostly for irrigation of crops and pasture. Although the lake level dropped 16
feet between 1894 and 1905, it later rose due to above normal precipitation and by 1911, had regained 18 feet
despite irrigation and export of water. The City of Los Angeles began to buy land and water rights in Owens
Valley in 1903 and in the Mono Basin in the 1930s. Today the City of Los Angeles owns 350,000 acres in Inyo
County and adjoining Mono County. The Department of Water and Power of Los Angeles (DWP) began to
export water from Owens Valley to San Fernando Valley (northern city limits of Los Angeles) in November 1913
and now exports about 350,000 acre feet annually. The diversion of Owens River water into the Los Angeles
Aqueduct denied Owens Lake its most regular and abundant source of water supply. The lake level began to fall
in 1917 and by 1926 the lake was dry and most of the artesian wells and flowing springs within Owens Valley
had dried up.
As a saline water body, Owens Lake was unsuitable as a source of irrigation water. The lake, however, was
navigable in the last century. In the 1870s Cartago, at the southern tip of the lake, was a bustling port. The 85’
long, shallow draft Bessie Brady steamboat carried silver-lead bullion from the Cerro Gordo mines in the Inyo
Mountains from the lake landing site of Swansea, northwest of Keeler, to Cartago and food, liquor, grain, lumber
and machinery, brought by mule teams pulling wagons from Los Angeles, from Cartago to Swansea. When the
Cerro Gordo mine shut down in 1879, Cartago’s busiest days had passed.
Prior to diversion of Owens River water by the DWP, Owens Lake once drew millions of ducks, geese, gulls
and other shore birds traveling between their breeding grounds in the north and winter range in the south. Joseph
Grinnell, an early 20th century naturalist, described a visit to the lake in 1917. “Great numbers of birds are in
sight along the lake shore - - avocets, phalaropes and ducks. Large flocks of shorebirds in flight over the water in
the distance. There must be literally thousands of birds within sight of this one spot.”
The Physical Characteristics of the Clay Playa (dry lake bed) of Owens Lake
(This discussion is mostly derived from Saint-Amand, D. and Saint-Amand, P. and C. Gaines. “Owens Lake, an
Ionic Soap Opera Staged on a Natric Playa,” Geological Society of America Centennial Field Guide--Cordilleran Section. 1987.)
The playa surface is hard in summer but softens in winter to the extent that the crust becomes efflorescent
(covered with crystals of salt) and can’t be traversed after receiving rain or snow. When the surface temperature
of the playa first reaches 95o F in the spring, polyhydrates (hydrates are any class of compounds that contain
chemically combined water) lose water of hydration and wet the playa surface; this process cycles diurnally
(encompassing the full 24 hours of the day).
The playa is covered with a thin layer of windblown sand mixed with clay, and an alkali crust. The clay
beneath is free of sand. When the surface is dry, the first few centimeters are a loose, fluffy layer of aggregated
clay particles. The crust when dry arches above the clays, but when wet, it collapses and the fluffy material
reverts to a reconstituted plastic clay. The clays are illite and montmorillinite, with some chlorite. The clay
beneath contains 40 to 50 percent water in about a 3 percent brine (water saturated with salt).
In summer, the upper clays dry and desiccation polygons, tens of feet across, form on the surface. The edges
of the polygons are covered with salts and cracks commonly appear at the edges. The clay, to a depth of 2 or 3
feet, breaks into blocks a foot or less in size, with lesser cracks an inch or so wide throughout the polygons. The
cracks at the edges of the polygons fill with sand and form clastic (comprised of fragments) dikes.
Alkali crusts form on playas where the water table is less than 10 feet below the surface. Crusts on playas
containing only sodium chloride, or nonhydrated minerals, are usually damp and hard. The crust on Owens Lake
contains sodium chloride, carbonate, sulphate, and minor amounts of borates, nitrates, potassium, and lithium.
The chemistry of the crust varies with the seasons. If the temperature is greater than 65o F (18o C), trona
(hydrous sodium carbonate or bicarbonate), thenardite (sodium sulfate) and halite (sodium chloride occurring in
crystals with perfect cleavage/rock salt) form. If enough rain falls, the precipitates dissolve and move below the
surface by the Soret effect, the forces of osmosis opposing those of capillarity. If the temperature rises above
155o F (65o C), thenardite and halite remain but trona converts to thermonatrite. The crust is hard and not easily
dislodged by wind.
In winter, when the temperature is below 65o F (18o C), trona and halite form and thenardite changes to
mirabilite (decahydrate [10 molecules of water] form of sodium sulfate) in the presence of water. A transient
dihydrate phase may precede the formation of mirabilite and it is likely that a septahydrate also forms. The
mirabilite occupies 4.1 times the volume of the thenardite. This breaks the crust and separates the clay grains.
With enough rain, it all dissolves and starts over; with less rain, more mirabilite forms. Upon exposure to dry air,
trona and halite (sodium chloride or rock salt) are stable, but the uppermost mirabilite dehydrates to amorphous
thenardite with a volume decrease. If the wind blows, a dust rich in sulphate-bicarbonate with particles of clay is
ablated (removed by wind erosion).
If the temperature drops below 50o F (10o C), mirabilite, amorphous sodium sulphate and halite are stable but
trona converts the natron (hydrated sodium carbonate) with a 4.8 times volume increase. The hydrates grow on
the bottom, encouraged by osmotic pressure operating in the same direction as the capillary forces, to bring water
to the surface through the clay. They dehydrate as they grow, encouraged in part by an osmotic gradient of the
water, to halite (sodium chloride or rock salt). Natron dehydrates to amorphous sodium carbonate, with a
concomitant volume decrease. Anhydrous sodium carbonate and sodium sulphate are thus present in a thin
farinaceous (flour-like or mealy) surface layer. Samples of the crust show no structure in X-ray crystallography,
except for halite and silica, but chemical tests reveal the presence of carbonate and sulphate ions. A 15 knot wind
will ablate (erode by the force of wind and become wind blown) a carbonate sulphate-rich dust and particles of
clay.
These conditions lead to dust storms when the wind blows in late fall, winter and early spring. The
stormsinterfere with air and surface transportation and cause health problems. Dust from the Owens Lake playa
has been tracked for 250 miles south. Several tons of material are removed per second during large windstorms.
Economic Exploitation of Mineral Resources on Owens Lake: Soda Production at Keeler
Keeler, currently a town of 100 inhabitants, is sited on the northeast shore of Owens Lake. Named after
Captain J. M. Keeler, who operated the steamship, Bessie Brady, on Owens Lake, Keeler once was home to 5,000
people, schools, churches, two hotels, theaters and other adult amusements in early days. A soda extraction plant
exploited the seasonal changes in the chemical composition of the crust until 1904. Lake water was concentrated
in shallow basins by solar evaporation. In hot weather, trona (summer soda) precipitated, was collected dried,
heated to drive off excess CO2, and sold as sodium carbonate monohydrate. In winter, when the temperature fell
below the stability field of trona, ice-like crystals of natron (winter soda) formed in the pools, were collected,
dehydrated, and sold as anhydrous sodium carbonate. Large amounts were used in China for making china. This
operation was abandoned when the lake water became so concentrated that trona precipitated in the lake. In
1911, carbon dioxide from limestones and dolomites of the Inyo Mountains was used to precipitate trona. The
operation continued until 1937.
Tectonics of the Lake Basin and the Formation and Economic Exploitation of Brine
In the northwestern corner of the lake, an area of distorted lake sediments has been uplifted, truncated, and
dextrally (to the right) offset by north south faulting. The fault is dextral while the fault on the other side of the
lake is sinistral (offset to the left). The two faults diverge slightly, hinting that the Coso Mountains are being
displaced southward, leaving an area of low tectonic relief into which the main part of the lake is dropping,
perhaps explaining the formation of this deep basin.
As the lake continued to dry, the brine (water heavily saturated with salt) became concentrated on the west
side of the lake. The Pittsburg Plate Glass Company plant at Bartlett Point, one of the world’s largest soda
producers in its time, operated from 1929 to the 1950’s. The brine was concentrated in evaporators; trona was
precipitated by carbonation, calcined, and CO2 recycled. Borax was recovered. Production ceased because of
changes in the water level of the lake. A 6,920 foot hole, drilled near the plant, passed through the lake bed
sediments and gravels but did not reach bedrock.
The brine pool, in dry years, is one to two feet deep and extends for about one mile north-south and a few
hundred feet east-west. Salts form on the bottom and float on the top as the many possible compounds
precipitate. When water has been dumped in the lake, or following rains, the pond is larger. The properties of the
brine pool change as salines are re-dissolved. Owens Lake contains 1.6 X 107 tons of anyhdrous salts of which
6.7 x 107 tons are sodium chloide, 6.3 x 107 tons are sodium carbonate, 2.3 x 107 tons are sodium sulphate, and
7.4 x 106 tons are potassium, boron, iron, aluminum, lithium and other elements.
On the shore of the brine pool, the surface temperature at noon often exceeds 165o F Just below the surface, a
gelatinous material, probably sodium silicate, thickens the brine. At a depth of a few centimeters, the temperature
is usually 75o F. Fresh spring water enters the playa, mixes with the brine and forms quicksand. Algae such as
Dunaliela salina, Dunaliela viridis, and halophilic bacteria such as Halobacterium, Chromatium, Ecto
thiorhodospira and Halococcus which have red carotenoids in their cells, color the water red. The microbiota
metabolize sulphates and modify the carbonate dioxide.
OWENS VALLEY WATER FOR LOS ANGELES AND ENVIRONMENTAL CONSEQUENCES
Diversion of Water From the Owens River
Water from the Owens River was first diverted into the Los Angeles-Owens Valley Aqueduct for delivery to
the city of Los Angeles in 1913. By the 1970s this delivery system (extended in 1941 to also take water from the
Mono Basin), owned by the City of Los Angeles and operated by Department of Water and Power (DWP),
supplied 80% of the water required by the City of Los Angeles. The city then (1970s) and now, not only owns a
system of dams, reservoirs, hydroelectric plants, canals and aqueducts, but also more than 90% of the land in the
Owens Valley, all of it purchased between 1904 and the mid-1930s. South of Big Pine, the Owens River flows
into the Tinnemaha Reservoir built and owned by the Los Angeles Department of Water and Power.
From 1913, the water received by the Tinnemaha Reservoir has been diverted into an uncovered aqueduct that
conveys the water southward through the Owens Valley to the Haiwee Reservoir located south of Owens Lake in
Rose Valley. Denied its former source of water, the former channel and ecosystems associated with the Owens
River below the Tinnemaha Reservoir, has undergone dramatic change.
The Haiwee Reservoir serves as the southern storage facility from which two aqueduct pipelines currently
convey water gathered from the Eastern Sierra watershed, streams of the Owens Valley and Mono Basin and
ground water pumped from the alluvial fill of the Owens Valley, to Los Angeles. The first aqueduct pipeline
became operational in 1913 while the second pipeline was authorized in 1963 and completed in 1970. Today, the
water from the Owens Valley-Mono Basin region supplies about 60% of the city’s annual water requirements,
about 350,000 acre feet annually, and the water is worth about $170 million per year (1998).
Pumping Ground Water From the Owens Valley Into the Los Angeles Aqueduct
Before the second aqueduct went into operation in 1970, as early as 1918 the city had pumped groundwater
into the aqueduct during arid climate cycles to makeup the run-off shortfall. With the opening of the second
aqueduct in 1970, the DWP began exporting groundwater via the aqueduct to Los Angeles on a regular basis.
Although the city had planned in the 1960s to pump 89 cubic feet per second (cfs) from the region’s underground
water table to fill the aqueduct and provide water to Owens Valley users, by the 1970s, new uses for water in the
Owens Valley necessitated the pumping of an additional 51 cfs of ground water.
Environmental Consequences of Owens River Diversion and Owens Valley Ground Water Pumping
Over the years, Inyo County officials, local residents and environmental activists had charged that the city of
Los Angeles and the DWP had stolen the water of Inyo County and turned a once green valley into a desert, and a
lake that was navigable into an alkali surfaced dry lake bed. Indeed, the feud between Los Angeles and the
Owens Valley is part of California lore, has been documented in books and film, and was highlighted when angry
valley farmers dynamited the aqueduct ten times in 1926. As the decades passed, negative environmental impacts
in the valley, that stemmed from the water diversions to Los Angeles, become increasingly obvious, and some
believe, hazardous. Owens Lake, deep enough for boats to cross from shore to shore at the end of the last
century, evaporated to became a salar dry lake bed (playa) covered with a thick crust of salt crystals, as its source
of recharge, the Owens River was diverted to the Aqueduct. The lower Owens River has been largely dry since
the DWP opened its diversion channel in 1913 thus dramatically affecting the ecosystem of the channel and flood
plain of the lower sixty miles of the Owens River before it reaches the shore of Owens Lake.
In addition to stream diversion, regular groundwater pumping by the DWP, beginning in 1970, lowered the
water table in the Owens Valley. Not only did some natural springs disappear, but the lowered water table
affected the ecosystem on the alluvial fans of the valley and some flora and fauna species are now considered to
be endangered. Finally, the dry alkaline dust on the surface of the 110 square miles of the dried-out bed of Owens
Lake is frequently lifted into swirling dust storms to become not only a nuisance, but also a health hazard to the
respiratory systems of 40,000 residents in the Owens and Indian Wells Valleys, from Lone Pine to Ridgecrest.
When winds exceed 20 miles per hour, perhaps as much as 11 tons of salty white crust hurls off the lake in a day.
Breathing unhealthful amounts of the fine particles, which can pierce deep into the lungs, triggers respiratory
problems such as asthma attacks. The salty powder also contains traces of hazardous substances including lead,
cadmium and arsenic. The dust reaches hazardous levels nineteen or twenty days a year on average at the small
town of Keeler on the northeast shore of Owens Lake.
LEGAL CHALLENGES TO THE DWP’S DIVERSION OF OWENS VALLEY WATER
Two related and contentious legal issues, regarding the DWP’s diversion of the Owens River and pumping of
the valley’s groundwater, were before adjudicating bodies until the late 1990s. Ultimately, Inyo County, Owens
Valley and environmental interests persuaded the courts, the California Air Resources Board and the Federal
Environmental Protection Agency to rule in their favor and force the city of Los Angeles to return some of its
water to Mono Lake, the Owens River and Owens Lake.
Restoration of Water Flow and Ecosystem Enhancement along the Lower Owens River Channel
In 1972, Inyo County sued the DWP contending that Los Angeles should have completed an environmental
impact report before it began regular pumping of groundwater. The county claimed that the pumping was
lowering the water table causing the widespread death of trees and other vegetation and destroying wildlife
habitats. The DWP rejected the claims of Inyo County and Louis H. Winnard, the general manager and chief
engineer of DWP, defended the addition of the second aqueduct and regular pumping of ground water when he
published “The Rape That’s Not; Relationship of Los Angeles, Owens Valley is One of Mutual Benefit” in
October 1976. Winnard’s argument and the arguments that the DWP subsequently and repeatedly made in court
to defend itself against the Inyo County law suit are summarized as follows:
History and Benefits of the DWP’s Los Angeles Owens River Aqueduct
(according to Louis H. Winnard in 1976)
California’s 1975-1976 winter drought, the worst in 45 years, and the September 1976 dynamiting of the
Alabama Gates on the Los Angeles Owens River Aqueduct focused new attention on the slim, 338 mile lifeline
that has provided Los Angeles with 80% of its water. Ever since William Mulholland completed the city’s first
Owens Valley aqueduct in 1913, the system had been both praised and criticized. It had been praised by those
who recognized it not only as an engineering accomplishment unparalleled since ancient Rome, but also as the
key to Los Angeles’ existence as a modern metropolis. The system had been criticized by those who believe that
the city stole the water from the Owens Valley, turning a once-verdant region into a desert. This latter version of
events is usually presented under a catchy heading: ‘The Rape of the Owens Valley.” According to the defenders
of the DWP’s L.A. Aqueduct system, even a cursory review of the relationship between Los Angeles and the
Owens Valley reveals how mistaken this “Rape of the Valley” view of history is. Defenders of the DWP L.A.
Aqueduct argued as follows:
1. The Owens Valley was never a lush agricultural region. Much of the valley floor, which receives less than six
inches of rain a year, has always been largely desert.
2. When Los Angeles first began to buy valley land in 1904, residents of the Owens Valley became concerned
that additional land purchases by Los Angeles would reduce the value of parcels remaining in private hands,
including town properties. Some violence ensued and, in the end, Los Angeles agreed to buy not only the
rural property of valley residents who wished to sell, but also parcels within the region’s towns. As a result,
the city owned more than 90% of the valley by the mid-1930s.
3. In order to stabilize and support the local economy, the city leased back most of its properties to valley
residents at favorable terms. Such land was mainly used for cattle grazing, which had always been the area’s
dominant agricultural activity.
4. In 1940, the city gave the Owens Valley economy another boost by releasing surplus water to ranchers for the
irrigation of alfalfa and other pasture crops.
5. When the valley’s business and civic leaders eventually requested that ownership of properties within town
limits be returned to residents, Los Angeles complied. Today, city-owned holdings within the region’s
towns are minimal. Moreover, Los Angeles now pays $4 million a year in Owens Valley property taxes,
nearly half the amount collected in the area, yet requires few services.
6. Los Angeles has also been working with the people of Inyo and Mono counties, the U.S. Forest Service and
the California Department of Fish and Game to develop the valley’s greatest asset, recreational land. Of the
307,000 acres of watershed now owned by the city, 240,000 acres have been leased to private interests for
ranching and agriculture with the stipulation that 75% of that land must be kept open to the public for
fishing, hunting and other recreation pursuits.
An Explanation of Why the DWP Constructed a Second Aqueduct
Owens Valley concerns about DWP exports of local water were heightened following the 1963 decision of the
Los Angeles Board of Water and Power Commissioners to authorize construction of a second, smaller aqueduct
from the Owens Valley. There were several reasons for this decision:
First, Los Angeles had rights to more water in the Owens Valley-Mono Basin region than the then existing
aqueduct could carry; thus, when California lost Colorado River water to Arizona as the result of an adverse
Supreme Court decision, it became necessary to obtain more water from the north. Second, water from the
Owens Valley was of better chemical quality than that from the Colorado River.
Third, the water from the second aqueduct would be less expensive than water from either the Colorado River
or the State Water Project. Finally, the state had warned Los Angeles that if the Mono Basin water was not used,
it could be made available to someone else.
DWP’s Contribution of Water to Owens Valley Users
It is also important to note that the Department of Water and Power, beyond its obligation to Los Angeles
water users, also serves many of Owens Valley’s 18,000 residents (2002). For example, the city distributes
enough water for irrigation and fish and wildlife purposes to support a population of 500,000 (the combined
population of both Inyo and Mono Counties in 2002 was 28,000). However, the city does not own all of the
valley’s water as some critics claim; many local people did not sell out in earlier years and the DWP does not
interfere with their water supply.
Moreover, while the average daily consumption of water per person in Los Angeles is 180 gallons, it is
approximately 1,000 gallons in Owens Valley towns served by DWP. The reason for this is obvious: Los
Angeles customers are metered and payment is based on use. But Owens Valley customers pay a flat fee
regardless of how much water they consume. And yet DWP’s attempt (in the mid-1970s) to encourage water
conservation by installing meters for the valley’s nonresidential customers was opposed in court by Inyo County.
In 1963, DWP agreed to rewrite leases to provide groundwater pumping for the irrigation of 15,000 acres of
city-owned land for alfalfa and cattle raising. Studies had indicated that crop productivity could be maintained on
less water if the ranchers would switch to sprinklers and modern irritation methods. The DWP helped ranchers
convert by amortizing the cost of permanent sprinkler systems. DWP’s goal in all this was to maintain the
valley’s level of agricultural productivity, while filling both aqueducts to their intended capacity of 666 cubic feet
per second (cfs). To do so, the DWP found it would have to pump 89 cfs from the region’s underground water
table. This water, which is naturally stored underground, has been pumped by the city during dry cycles dating
back to 1918.
Why DWP Increased the Amount of Water Pumped in the Owens Valley and Consequences
But by 1970, when the second aqueduct was placed in service, several things had happened that the DWP had
not anticipated in 1963. During the intervening years the city had agreed to irrigate an additional 4,000 acres of
pasture land and to make water available for recreation, for fish and wildlife enhancement projects and for the
expansion of two fish hatcheries. When the amounts of water were added up, the DWP had to increase its
pumping from the originally planned 89 cubic feet per second (cfs) to 140 cfs. The difference of 51 cfs was
needed to meet additional Owens Valley needs. The amount of water exported to Los Angeles since completion
of the second aqueduct in June 1970 did not exceed what was anticipated in 1963.
Although Inyo County’s 1972 lawsuit suit alleged that the pumped groundwater was going to Los Angeles
and unless the removal of underground water was stopped, native plants and wildlife as well as the entire valley’s
agriculture would be severely damaged, Winnard responded that the first charge was untrue since the additional
pumped water benefited the Owens Valley and the second charge represented a gross exaggeration The irrigated
agricultural land leased from the city, including the new 4,000 acres, would not be affected except in years of
severe drought when the city would also be similarly affected. Moreover, studies at that time indicated that, at
most, 22% of the native shrubs and grasses in the areas where groundwater is less than 15 feet from the surface
would be gradually affected over a long time span. This represented only about 1.5% of the total Owens River
watershed. In the first six years of pumping groundwater, from 1970 to 1976, there was little documented change
in the valley that could be attributable to the pumping.
Moreover, although Inyo County officials argued that Los Angeles should decrease its water exports from
Owens Valley and substitute water from other sources, the ramifications of such a move would extend beyond the
Owens Valley, since the Los Angeles aqueduct was and remains the only system bringing water into Southern
California that produces electricity instead of consuming it. If the electricity produced by the hydroelectric plants
along the aqueduct system were to be replaced by power from plants using fossil fuels, approximately 2 million
barrels of oil a year would have to be burned in the South Coast Air Basin. In addition, the alternative water
supply, which would come from the California Aqueduct, would have to be pumped with electricity. Supplying
that power would require burning another 2.5 million barrels of oil per year, about half of it in the South Coast
Air Basin. Thus if Inyo County officials had their way, not only would Los Angeles have been deprived of an
important source of vital water, but all of Southern California would have also suffered a reduction in air quality.
Louis Winnard’s 1976 defense of the expansion of the DWP’s water transfer system and explanation of its
benefits was countered by various critics. One of the more eloquent and humanistic critiques was penned by long
time Owens Valley resident and naturalist/botanist Mary DeDecker in her article “Owens Valley, Then and Now”
which appeared in the Inyo Museum News Bulletin of August 1977.
Settlement of the Lawsuit
The law suit remained unsettled for twenty five years and was joined by four other interested parties before a
January 1997 agreement was reached between the six contentious parties. Signaling the end to a quarter-century
of politically charged litigation over Los Angeles’ use of Owens Valley ground water, a state appellate court ruled
in May 1997 to accept the agreement negotiated in January 1997 which would help repair some of the
environmental damage to Owens Valley. Under the terms of the agreement, accepted by the DWP, Inyo County,
the State Department of Fish and Game, the State Lands Commission, the Sierra Club and the Owens Valley
Committee (an amalgam of local environmental organizations), the DWP agreed to restore the flow of water once
more through the lower 60 miles of the Owens River and provide for establishment or restoration of several
wildlife habitats at lakes, ponds and wetlands and a new fishery along the re-watered riverbed.
Solving the Dust Storm Pollution Problem
Since 1982, the Great Basin Unified Air Pollution Control District (GBUAPCD) had explored ideas for
remedying the problem of fine particle air pollution dust storms off the dry bed of Owens Lake. The GBUAPCD
is comprised of six county supervisors and one mayor from three Eastern Sierra counties, Mono, Inyo and Kern.
Under a 1983 California law, Los Angeles was required to fund “reasonable” measures to study and curb the
lake’s dust storms. Since 1983, the GBUAPCD had spent $20 million of DWP funds studying various remedial
options ranging from construction of fences to refilling the lake.
The federal Clean Air Act requires states to clean up and largely eliminate the fine pieces of air pollution
called particulates by the end of 2001 or seek a five-year extension from the U. S. Environmental Protection
Agency. In 1993, the U. S. Environmental Protection Agency (EPA), the responsible federal government agency
for enforcing the Clean Air Act, declared that the Owens and Indian Wells Valleys experienced the worst
particulate pollution in the United States and ordered state and local authorities to clean it up. On about 20 days a
year, during the worst of the dust storms, monitors established by local air control officials have found that
pollution from dust particles soars to 25 times the federal standard of 150 microns per cubic meter.
Although no government agency had ever undertaken a long-term heath study in the two valleys, the EPA
stated that these particles, each about one-seventh the diameter of a human hair, constituted a serious air pollutant
that may cause severe respiratory illnesses including emphysema and that children, the elderly, and people
suffering from heart and lung disease, were especially at risk. In addition, the EPA stated that the dust clouds
contain carcinogens such as nickel, cadmium and arsenic. At the China Lake Naval Weapons Station in the
Indian Wells Valley, planes were grounded and the testing of missiles came to a halt (they still are) when the dust
storms blew through the area. The California Air Resources Board was given until February 8, 1997, to submit a
dust abatement plan. The deadline passed without any action.
The Great Basin Unified Air Pollution Control District versus the City of Los Angeles
In July 1997, the Great Basin Unified Air Pollution Control District, which held the city of Los Angeles
legally responsible for remedying the dust storm problem, took steps to force the city to return a substantial share
of its coveted aqueduct water to Owens Lake to curb the dust storms that periodically blow through valley towns.
The Control District’s plan would have forced Los Angeles to surrender about 15% of its cheapest water (about
51,000 acre-feet per year, the equivalent of 43 million gallons daily) in order to cover about 35 square miles of
Owens Lake bed (1/3 of the lake) with a mix of shallow water, gravel and vegetation. If implemented, the plan
would have required the flooding of 13 square miles (8,400 acres) of the northeast portion of the lake bed,
planting vegetation on 14 square miles (8,700 acres) in the southeast portion of the lake bed and covering 8
square miles (5,300 acres) in the east and south portions of the lake bed with a four inch thick bed of gravel.
GBUAPCD engineers believed that implementation of this plan would eliminate 99% of the dust within five
years. This plan would have required DWP customers in Los Angeles to pay between $91 million and $300
million, plus annual costs of $25 million to replace the lost water with expensive limited supplies from northern
California or the Colorado River. The plan was designed to control salt crystals that sit atop the sprawling lake
bed and when whipped up by winds, drape the Owens Valley with tons of white powder. The City of Los
Angeles officials rejected the GBUAPCD proposal on three grounds; the proposal, if implemented, would have
had the effect of violating the city’s legal rights to Owens Valley water as already determined by state court and
water commission decisions in earlier decades; implementation of the remedy as proposed by the GBUAPCD
would be exorbitantly expensive to Los Angeles; DWP experts and officials doubted that the remedy proposals
would be effective in solving the wind-blown dust storm problem and doubted that the dust problem was as grave
as valley residents claimed. City officials claimed that only 12 tons of dust on average blow off the lake bed per
year instead of 300 tons as claimed by GBUAPCD.
In August 1997, EPA officials, fed up by what they regarded as foot dragging by the state and the city of Los
Angeles, issued a warning that demanded a clean up effort begin no later than August 20, 1999. The 1999
deadline might have been enforceable in that the EPA stated that if plans for clean up had not been approved by
the deadline date, EPA would clean up the dust storm problem itself, bill the state and impose sanctions that
would mean the state would lose federal highway funds. The threat of sanctions stimulated state officials to
pressure the California Air Resources Board to pressure Los Angeles and the GBUAPCD to find a solution.
A Compromise Solution to the Owens Lake Region Dust Storm Problem
On July 15, 1998, Owens Valley officials and Los Angeles authorities struck a historic deal designed to bring
an end to the troublesome dust storms originating from the Owens Lake dry bed. The Los Angeles Department of
Water and Power (DWP) agreed to begin work at the lake bed by 2001 and established 2006 as the target date for
ensuring that people living in the Owens Lake Basin will be able to breath air that meets federal health standards.
Officials of the Great Basin Unified Air Pollution Control District agreed to accept a modified reduction in the
improvements that they had sought and to permit improvements to be phased in gradually. According to the
terms of the compromise agreement, Los Angeles is to treat at least 22.5 square miles within 36 designated square
miles of the lake bed. Ten square miles of the 110 square mile lake bed will be treated by the end of 2001, an
additional 3.5 square miles in 2002 and three more in 2003. Thereafter, at least two square miles must be treated
every year until the Great Basin air agency determines that federal clean-air standards are met. The plan is to be
reviewed in 2003 to determine if the pace of treatment must be accelerated to achieve the EPA air quality
standards by 2006. The DWP can design its dust-control strategy with a mix of three different techniques:
shallow flooding of parts of the lake bed, planting vegetation and depositing a gravel cover on the lake bed. The
lake will not be refilled, but the first 10 square miles are likely to be permanently covered with a few inches of
water, enough to halt the initiation of dust storms. The project is expected to cost $120,000,000 and the city may
permanently lose about 40,000 acre feet of water a year.
It is hoped that most of the needed water can be obtained from Owens Valley ground water sources instead of
from the aqueduct. The California Air Resources Board approved the plan in July 1998; the U.S. Environmental
Protection Agency granted a five-year extension of the Clean Air Act provision which requires states to clean up
particle pollution by 2001 or seek an extension until 2006 and formally approved the compromise agreement on
August 18, 1999. Implementation of the earliest stages of the improvement plan began in 2001 when the DWP
contracted with private sector firms to design and implement the plan’s detailed components. Rewatering of
about 10 square miles of the lake bed began in November 2001. Although the primary objective of the plan is to
reduce dust pollution, newly delivered water to the lake may stimulate dormant algae to germinate and become a
food resource for brine flies which in turn are likely to support an enlarged migratory bird population.
Summary: Owens Valley PM-10 Planning Area Demonstration of Attainment State Implementation Plan
2003
ALLUVIAL FANS OF THE OWENS VALLEY
North of the Alabama Hills, a west to east profile or transect across the Owens Valley reveals an asymmetrical
arrangement in the height and areal extent of the valley’s coalescing alluvial fans. Alluvial fans originating on the
west side of the valley are built by deposits of streams discharging from the Sierra Nevada Mountains and are
higher in elevation at their apex than are the alluvial fans originating on the east side of the valley where streams
discharge from the Inyo Mountains.
Moreover, the alluvial fans originating from the lower slopes of the Sierra Nevada Mountains incline
downward and eastward well beyond the center of the valley to reach their lowest elevations at the bank of the
north to south flowing Owens River, the major drainage channel for the valley. The streams discharging from the
Sierra Nevada Mountains carry much larger volumes of water and much larger sediment loads when compared
with the streams discharging from the Inyo Mountains at the east side of the valley. It is no accident that the
alluvial fans originating on the west side of the valley have forced the Owens River drainage channel and flood
plain to assume a location near the eastern edge of the Owens Valley. In contrast, the alluvial fans originating
from deposits of streams discharging from the Inyo Mountains, carry less volume of water and smaller sediment
loads which in turn produce smaller fans with a much smaller areal extent compared to the fans originating on the
west side of the valley.
Alluvial Fans: Stage, Structure and Process
An alluvial fan consists of stream deposits, the surface of which forms a segment of a cone that radiates
downslope from the point where the stream emerges from the mountain area. Some authors have used the
term ‘alluvial cone’ to describe small fans steeper than 20 degrees that are formed by both fluvial deposition and
mass wasting while others have used it as a synonym for an ‘alluvial fan.’ Although the term, “alluvial fan” was
first coined by F. Drew in 1873 in reference to features in the upper Indus basin, A. Surell, in 1841, appears to
have been the first observer to discuss fans as landform features. Alluvial fans are commonly found in arid and
semiarid regions with tectonically active mountains where there is an abundant supply of sediment. Classically,
the term alluvial fan refers to features deposited by periodic fluvial processes and debris-flow processes
(excluding other forms of mass wasting) during and following precipitation and runoff in mountains located in
arid and semi-arid climatic environments.
An alluvial fan may consist of debris-flow deposits, water-laid sediments, or both. The highest point on
the fan, where the stream leaves the confines of the mountain, is the fan apex. The overall radial profile of an
ideal alluvial fan surface (longitudinal profile) is concave, while the cross-fan profile (parallel to the mountain
front) is convex. In plan view the deposit is typically fan shaped, with contours that are convex outward from the
mountain front.
Fans often have stream channels that are incised into the fan surface. When the particular case known as
‘fanhead trenching’ occurs, the incised channels are generally deepest at the fan apex and decrease progressively
down-fan until the stream channel and the fan surface intersect. This point on the fan surface is called the
intersection point.
Alluvial fans may coalesce along the piedmont (the outward sloping base of a mountain front) as the
sediment deposits from neighboring mountain streams are laid down along the neighboring flanks of their
fans. Such a coalescence produces a bajada, a series of coalescing alluvial fans where it may prove difficult
to distinguish the edge of one fan from its neighbor as their respective sediment deposits are interwoven and
interlayered. Coalescence occurs first at the neighboring bases of two adjacent fans. Over time, continued
deposition along the line of coalescence will extend the height of the coalescence up the slopes of the neighboring
fans and thus enlarge the extent and height of the bajada along the piedmont.
Although alluvial fans may form in areas where tectonic uplift is not an important factor, they are
especially prominent where uplift of mountainous regions provides a continual supply of fresh debris from
steep drainage basins. Regional analysis of landforms in the American West has revealed that the tectonically
active Basin and Range Province has an abundance of alluvial fans, while in the tectonically stable areas of southcentral Arizona, the pediment is the dominant landform. In areas where tectonic activity is decreasing, alluvial
fans may be replaced by pediments as the typical landform. The Antelope and lower Owens Valleys both display
excellent examples of coalescing alluvial fans developed along the alignment of uplift.
The tectonic influence on the development of alluvial fans may be examined in terms of fan
entrenchment, fan segmentation, and the sedimentology, shape and thickness of both modern and ancient
alluvial fan deposits. The rate of tectonic uplift in mountain areas relative to the rate of stream channel
downcutting, largely determines the locus of deposition and the thickness of the alluvial fan deposit. There are
probably two phases of development for alluvial fans that can be identified; they are related to differential uplift
of the mountain block with respect to the valley block. The first type of fan develops where the rate of uplift is
greater than the rate of stream channel downcutting, resulting in deposition adjacent to the mountain front.
Continued tectonic uplift results in the accumulation of thick alluvial fan deposits.
The second type occurs where the rate of channel downcutting at the mountain front exceeds the rate
of uplift of the mountain mass; the fanhead becomes entrenched and the locus of deposition moves downslope
from the fan apex. This situation may be associated with a decrease in the rate of uplift. If the rate of tectonic
uplift does not increase so that it exceeds the rate of stream channel downcutting, the fan head area will be
removed from active deposition and soil development will take place on that portion of the fan surface.
Although the overall radial profile of an alluvial fan is concave, it is not always a smooth exponential
curve. Instead, the connection of a series of distinct straight or, less commonly, concave segments that
have progressively lower gradients downslope, form “segmented fans.” Two types of segmented fans have
been identified and are related to changes in stream channel slope upstream from the fan apex due to tectonic
uplift, climatic change, or base-level change.
The first type occurs in areas characterized by rapid, intermittent uplift. Mountain stream gradients will
steepen and, as a result, a new and steeper fan segment will be constructed upslope of the previous segment. The
opposite situation occurs where either a reduced rate of tectonic uplift or a climatic change induces accelerated
stream incision and rapid down-fan movement of the locus of deposition, resulting in a new fan segment with a
lesser gradient. Therefore, in the first situation, fan segments are steeper and younger in the up-fan direction,
whereas in the second situation, fan segments are younger and gentler in the down-fan direction.
BIG PINE VOLCANIC FIELD BETWEEN INDEPENDENCE AND BIG PINE
The Big Pine Volcanic Field is the consequence of at least four episodes of volcanic activity that occurred
between 100,000 to 200,000 years B. P. This eruptive activity gave rise to the volcanic domes, vents and flows
that sprawl across the Owens Valley between Independence and Big Pine. Red Cinder Cone and Red
Mountain (600 feet high and partially buried by later developed alluvial fans) are two of the most prominent of
the 30 or more individual vents identified in the Big Pine Volcanic Field.
MAMMOTH MOUNTAIN, THE MAMMOTH CREEK MEADOWS AND EMBAYMENT,
Commonly thought of as a part of the Sierra Nevada Mountain Range, Mammoth Mountain, although
adjacent, is geologically unrelated to the landform unit known as the Sierra Nevada. Instead, Mammoth
Mountain anchors the southern end of a south to north chain of young volcanoes that extends thirty miles
northward to Mono Craters in Mono Basin and is the oldest and highest (11,053’ at the summit) of the
volcanic features located along this alignment. The earliest volcanic flows originating from this site occurred
as early as 370,000 B.P. and formed the base of the existing mountain. The construction of the major mass of
Mammoth Mountain is the result of at least ten subsequent eruptive events, beginning around 200,000 B.P.,
resulting in a composite dome built piecemeal by recurring viscous extrusions of gray or reddish lava with the
upper coulee being formed around 150,000 +/- 5,000 B.P. Although no lava has erupted in the last 50,000 years,
the volcano may not be extinct. Only 500 years ago a steam explosion blasted the north slope and steam still
issues from fumaroles at several sites on the cone. In sum, Mammoth Mountain, sited at the western-most edge
of the Long Valley Caldera, consists of at least 20 overlapping domes and silicic lava flows.
Although at a distance its profile is that of a typical, symmetrical volcanic dome, at closer range its surface is
markedly irregular. The surface shapes of this volcano are partly due to sculpturing by water and ice and partly to
the eruption of lava flows that were too small and viscous to spread out, cooling instead as stubby, steep-sided
blobs on the volcano’s flanks. The volcano’s lava is sprinkled with tiny clear to whitish feldspar crystals and
shiny black flakes of mica.
Immediately north-northeast of the lower slopes of Mammoth Mountain, and adjacent to the northern fringe
of the Town of Mammoth Lakes, are the three Mammoth Domes (coulees) that were recently formed (3,5001,500 B.P.) by silicic viscous extrusions associated with the fracture zone that extends from Mammoth Mountain
to Mono Lake. The Mammoth Domes are prominent, covered by forest where sufficient soil exists for root
penetration and effectively limit the northward expansion of the Town of Mammoth Lakes (although limited
residential development occurs on their lower slopes).
East of Mammoth Mountain and north of Mount Laurel the plain of Mammoth Creek Meadows
extends across the Mammoth Embayment to Highway #395. From Highway #395, highway #203 leads
westward, steadily upslope, toward the Town of Mammoth Lakes and eventually to the northern slopes of
Mammoth Mountain, Minaret Summit and Devil’s Postpile. The lower 2-3 miles of #203 climbs the relatively
gentle gradient of the Mammoth Creek Meadows that are carpeted with a thin veneer of alluvium and
glacial ground moraine that covers a ropy and locally scoriaceous surface atop basaltic lava flows
interspersed with ground moraine deposited during the retreat of glaciers that occupied the Mammoth
embayment at various times during the Pleistocene era.
Basalt flows at the surface are mostly Quaternary in age and originated from the northwest, probably from the
vicinity of Mammoth Mountain if not the mountain itself. Surface morainal deposits, including boulder erratics,
overlay basalt flows that date to 190,000 B.P. which lie atop still older basalt flows dating to 280,000 B.P. Still
deeper are glacial till deposits of the Tahoe I/Hobart glaciation (260,000-400,000 B.P.) that rest upon older basalt
flows dated to 440,000 B.P.
MAMMOTH LAKES BASIN
The Mammoth Lakes Basin incorporates, and is enclosed by, a variety of geological features. To the north are
the lava bluffs and extensions of Mammoth Mountain’s southern volcanic slopes. Indeed, dark and light colored
lavas that flowed from Mammoth Mountain vents form the surface of the bluffs, at the foot of Lake Mamie, over
which the Twin Falls spill to drop more than 100 feet to the Twin Lakes below. Westward, the skyline is formed
by the Mammoth Crest, the surface of the granitic batholith of the Sierra Nevada. To the south are the
metamorphosed volcanic materials that form Panorama Dome and Red (or Gold) Mountain (the site of a mining
boom in 1878-80). Eastward beyond the drop of Mammoth Falls is the Mammoth Embayment widening into the
Mammoth Meadows of the Long Valley Caldera with the White Mountains forming the eastern skyline. The
material of the surface of the Mammoth Lakes Basin varies in its content; volcanic ejecta, metavolcanic rock,
glacial debris including erratics, and the granite surface of the batholith are all present. Crystal Crag (10,364’),
the prominent granitic spire that towers over the surrounding basin lakes, is an island of resistant rock around
which flowed the two arms of a glacier. Crystal Crag is a remnant of a once high ridge separating the drainages
of Crystal and T J Lakes, two of the smaller lakes in the basin.
The Mammoth Lakes Basin is located at the western-most edge of the Mammoth embayment and over 800’1,000’ above the hardened lava flows and glacial till-strewn plain of the Mammoth Meadows below. The lowest
of the Twin Lakes at 8,620’ is the first lake encountered during the ascent of Lake Mary Road. One of thirteen
lakes located in the Mammoth Lakes Basin (none named Mammoth Lake), Lower Twin Lake is drained by
Mammoth Falls which forms the major source of Mammoth Creek as it spills over a lava ledge (to become
known as Hot Creek beyond Highway #395). Each of the thirteen lakes is a feature derived from the activity of
glaciers that occupied the Mammoth embayment and its tributary valleys during the Pleistocene era. The lakes
occupy the lowest part of the cirques and other depressions carved and deepened by moving ice that has since
melted away. The mountain lakes in these glacially deepened hollows are known as tarns or morainal lakes.
Some of the lakes are deeper than the depth of the depressions in which they sit due to the presence of dam-like
recessional moraines which are located at the lower end of the lakes and trap the water behind the inner slope of
the moraine.
Lake Mary (8,896’-8,898’), the largest of the Mammoth Basin lakes connects to Lake Mamie (8,898’-8,900’)
which drains eastward through a flow control gate where the exiting water plunges 250-300 feet over the Twin
Lakes Falls into the Upper Twin Lake below. Lake George (9,008’), the highest of the Mammoth Lakes
accessible by car, is located at the foot of Crystal Crag and receives the drainage of Crystal Lake via the Crystal
Falls. All of the above identified lakes contribute to the water supply of the City of Mammoth Lakes. At the
terminus of Lake Mary Road is Horseshoe Lake (8,950’), the only lake in the Mammoth Basin with wide sandy
shores (in most years) and not connected to the rest of the drainage system. Most of the sand is really pumice and
the lake loses water through underground drainage into the porous volcanic rock in which it lies. Horseshoe
Lake’s surface level varies considerably with the season and from year to year.
FOREST DEATH AT MAMMOTH LAKES
In 1994, scientists confirmed that volcanic gases, particularly carbon dioxide, were rising though the
joints, fissures and pore space in the rock and soil of Mammoth Mountain. Believed to be emitted from the
underlying magma, the volcanic gases have proven to be deadly to the coniferous trees on three sides of the
mountain. The site of the most extensive tree kill is at the eastern end of Horseshoe Lake. At the Horseshoe
Lake site, 9,000 feet above sea level on the southern slopes of Mammoth Mountain, a dramatic increase in the
incidence of tree deaths was reported in 1991-1992. By 1994, suffocation by carbon dioxide gas had been
established as the cause of death and the areal extent of tree mortality had expanded. By summer 1997, lifeless or
dying coniferous trees occupied 170 acres on Mammoth Mountain slopes.
Samplings taken in August 1995, revealed as high as a 96% level of carbon dioxide in soil gases at depths of
one meter or less. The toxic level for trees is 30% and soil readings normally are only in the tenths of 1%. CO2
gas is heavier than air and biologists believe that carbon dioxide from the fumes is displacing a lot of normal soil
oxygen, damaging the plants’ ability to absorb water and nutrients through their root systems. In 1995, tree roots
were being subjected daily to 1,200 metric tons of gas that oozed upward through the forest soils. In the summer
of 1997, although the daily volume of gas seepage was down to less than half the maximum levels in the earlier
years of the 1990s, the gas could still pool and continues to be deadly to tree life today. When CO2 gas leaks from
soil, it can collect in snowbanks, depressions and poorly ventilated enclosures such as tents and cabins, thus
posing a danger to people. Carbon dioxide can be toxic to humans beginning at a 3% concentration level (there is
no danger to human or plant life in the open air in the vicinity of the emissions).
Studies suggest that at least 1200 tons of carbon dioxide were being released each day at the Horseshoe
Lake site (equal to the release at such active volcanoes as Hawaii’s Kilauea). In 1978-1980, scientists
detected the beginning of a magma intrusion into the Long Valley Caldera accompanied by swarms of
earthquakes (the highest magnitude earthquake was recorded at over 6.0 on the seismometer.). The center of
Long Valley has experienced an increase in elevation of approximately 2.5 feet since 1978-1980 and
seismometers have been recording on-going earthquake swarms ever since. The seeping of gases into the soils at
the Horseshoe Lake site apparently began in 1989 right after a renewed series of earthquake swarms occurred
under Mammoth Mountain. CO2 and other volcanic gases, like helium, seeping from Mammoth Mountain appear
to be leaking from a large reservoir of gas supplied by repeated intrusions of magma. It is likely that fracturing
and movement of rock material at depth opened deep fractures increasing the rate of gas seepage.
EXTRUSIVE INGEOUS ACTIVITY IN LONG VALLEY AND THE MONO BASIN AREAS
LONG VALLEY, MAMMOTH LAKES, MONO BASIN - SOME DATES
I. Extrusive Igneous Features and approximate dates of their formation.
A. Inyo Craters (phreatic cones)
650 +/- 200 B.P.
B. Obsidian Dome
5-600 B.P.
C. Panum Crater (North Crater)
700 B.P.
D. North Coulee (one of Mono Craters)
1,800 B.P.
E. Mono Craters, Domes, Coulees
6,400 - 10,200 B.P.
F. Mammoth Domes (Coulees)
1,500 +/- 500 B.P.
G. Mammoth Mountain (upper coulee)
150,000 +/- 5,000 B.P.
H. Mammoth Mountain (earliest flows)
370,000 +/- 4,000 B.P.
Last significant eruption about 50,000 B. P.
H. Devil's Postpile
630,000 +/- 5,000 B.P.
I. Long Valley Caldera (explosion)
760,000 +/- 4,000 B.P.
CALDERAS, LONG VALLEY CALDERA, THE VOLCANIC TABLELAND, BISHOP TUFF
AND THE HOT CREEK
Calderas
A caldera is a large circular or semi-circular shaped volcanic crater that may be many times larger
than the volcanic vent system that produced it. Most calderas form when the crater floor collapses into a
vacated magma chamber beneath the volcano a (as occurred when Mount Mazama collapsed to form Crater Lake,
Oregon) or when a volcano’s summit is blown off by exploding gases (as occurred at Mount St. Helens,
Washington in May 1980).
The molten rock, or magma, that feeds such volcanic eruptions is a combination of lava and volcanic
gases. When the lava is ejected, it crystallizes to form extrusive igneous rocks. The gases are held within
the magma by the confining pressure of the magma chamber or overburden. At the start of an eruption,
the magma effervesces and the gases separate out. The gaseous mixture commonly includes water vapor,
hydrogen, hydrogen sulfide, sulfur dioxide, carbon monoxide, carbon dioxide, and hydrogen chloride. The
manner in which gases separate from the magma determines the character and violence of an eruption.
The degree of violence with which a volcano erupts relates closely to the viscosity and gas content of the
magma. Magma viscosity in turn is influenced by two factors: 1) the temperature at which a magma
solidifies, and 2) the silica content of the magma. Silica- and gas-rich magmas, such as rhyolite, are
significant in the formation of large calderas because they tend to produce larger and more explosive
eruptions than mafic magmas (rich in magnesium and iron), such as basalt.
Because mafic magmas are low in silica content, they tend to lose their gas and flow easily. For
example, the often-photographed flowing rivers of red-hot basaltic lava in Hawaii are of mafic composition. In
contrast, silica rich magmas are very viscous and do not flow freely. The high viscosity inhibits gas separation
and escape. Silica-rich magma eruptions can be extremely violent, and the ejecta and lava flows look much
different than the Hawaiian-type runny-lava flows. Eruptions that are dominated by magma high in silica
and dissolved gases seldom form liquid lava; more commonly they send pumice and fine ash explosively
into the sky as the magma leaves the confining pressure of the magma chamber.
The largest known calderas are those associated with silicic pyroclastic eruptions and are more than 40
miles in diameter. Catastrophic eruptions and subsequent collapse are followed by a gradual raising of the
floor as magma intrudes upward once again into the chamber that originally formed the caldera. A
“resurgent dome” forms within the caldera over the next several hundreds to thousands of years. The
basic structure of a resurgent caldera is a broad depression with a central domed uplift.
Long Valley Caldera represents the collapse of the site of the 760,000 B. P. massive explosion and
extends over an elliptically shaped area that is twenty miles across, east to west, 10 miles wide, north to
south, and extends over about 170 square miles. The brief and intensely violent history of the Long Valley
region began several million years ago when molten magma began to collect a few miles beneath the valley floor.
The magma began to erupt, producing a cluster of volcanoes, stubby domes of extremely viscous rhyolite magma
that rose where the caldera would later form. The only volcano that survived the dramatic eruption is Glass
Mountain, a large dome complex of rhyolite and obsidian that formed between one and two million years ago.
The eastern half of the caldera, Long Valley proper, is a broad grass and sage-covered valley of low relief. The
western half of the caldera encloses the Town of Mammoth Lakes and is a forested area of higher relief.
Mammoth Mountain, the three Mammoth Domes (1,500-500 B.P.), the three Inyo Craters, Glass Mountain
and Crowley Lake are all within the Long Valley Caldera. Caldera is Spanish for cauldron.
An examination of the local geology reveals pre-Tertiary basement rocks in the vicinity of the Long Valley
caldera that include Jurassic and Cretaceous granite rocks of the Sierra Nevada batholith, and Paleozoic and
Mesozoic metamorphic rocks of the Mount Morrison and Mount Ritter roof pendants. Thick sequences of late
Tertiary pre-caldera volcanic rocks overlie the basement rocks. Evidence of the earliest volcanism associated
with the Long Valley caldera magma chamber originated from upwelling deep-crustal magma culminating in
eruptions starting 3.2 million years ago. These older basaltic and andesitic lava flows are scattered over a 1,500
square mile area around the caldera. Intermittent associated volcanism continued from 3.2 million years ago to
800,000 years ago. During this period a large shallow magma chamber formed beneath Long Valley.
The main eruption began about 760,000 years ago, when magma heavily charged with red-hot gases
exploded from the top of the magma chamber to form the Bishop Tuff. Volcanic gases (mainly steam and
carbon dioxide) collect at the top of a mass of molten magma. This magma mass contained enough gas under
enough pressure to produce a tremendous explosion that blew ash and pumice several miles into the air.
Evidence of this early phase of the eruption survives in a thin layer of white ash at the base of the Bishop
Tuff.
Volcanic ash consists of tiny jagged particles of rock and natural glass blasted into the air by a gas rich
volcanic explosive event. Small jagged pieces of rocks, minerals and volcanic glass the size of sand and silt
less than 1/12 inch (2 millimeters) across erupted from a volcanic vent are called volcanic ash. Very small
ash particles can be less than1/25,000th of an inch (0.001 millimeter) across. Though called “ash,” volcanic
ash is not the product of combustion like the soft fluffy material created by burning wood, leaves or paper.
Volcanic ash is hard, does not dissolve in water, is extremely abrasive, mildly corrosive and conducts
electricity when wet. Formed during explosive volcanic eruptions, such explosions occur when gasses
dissolved in molten rock (magma) expand and escape violently into the air and also when ground water is
heated by magma and abruptly flashes into steam. The force of the escaping gas violently shatters solid
rocks. Expanding gas also shreds magma and blasts it into the air where it solidifies into fragments of
volcanic rock and glass.
Once in the air, hot ash and gas rise quickly to form a towering eruption column, often more than
30,000 feet high as it was at Long Valley Caldera. Larger rock fragments, more than 2 inches across,
ejected the by the explosion typically fall within a few miles of the eruption site. However wind can
quickly blow fine ash away from the volcano to form an eruption cloud. As the ash drifts downwind from
the erupting vent, the ash that falls from the cloud typically becomes smaller in size and forms a thinner
layer on the ground. Ash clouds can travel thousands of miles and ash from the 760,000 year old eruption
at Long Valley has been found as far east as Nebraska and as far south as San Diego. As magnificent as
the eruption of ash at the Long Valley Caldera certainly was, it was only a preamble to the truly awesome
display that soon followed.
The caldera opened as about 150 cubic miles of ejecta (mostly high-silica rhyolite) boiled out of the
magma chamber from a depth of about 4 miles below the earth’s surface, quite possibly in a single
enormous blast. The magma erupted from a set of vents aligned along an arc or series of ring shaped faults just
inside the margin of the present caldera to form a two-mile-deep oval depression. It was an event of incredible
intensity that has not occurred elsewhere on earth during historic time. About half of the erupting thick
cloud poured across the surrounding country-side as a series of ground-hugging ash flows at a
temperature of about 1,500o F. This flow of red hot ash spread in all directions at speeds up to 100 miles
per hour, devastating everything in its path. One great ash flow poured south down the Owens Valley, at
least as far as the present site of Bishop; another spread west over the crest of the Sierra Nevada and into
the valley of the San Joaquin River, while still another flowed northward almost to the shores of ancient
Mono Lake. Remains of this widespread pyroclastic unit, known as the Bishop Tuff, form bold
escarpments and other prominent landscape features in Inyo and Mono counties.
Although the caldera formed as the Bishop Tuff erupted, post-caldera volcanism continued to alter the
local geology. When a large volume of molten magma erupts, it leaves the roof of the subterranean magma
chamber unsupported and the roof of the magma chamber fell in (subsided) as the chamber emptied. When it
first formed the depression was about two miles deep, but the erupting Bishop Tuff almost immediately filled
about two thirds of this cavity and formed the present 10 x 20 miles oval depression of Long Valley Caldera.
Subsequent eruptions from the Long Valley magma chamber were confined within the caldera and first consisted
of extrusions of relatively hot (crystal-free) rhyolite 700,000 to 600,000 years ago as the caldera floor was
upwarped to form a resurgent dome. The summit of the resurgent dome in the center of the caldera was raised
about 1,500 feet above the adjacent caldera floor. Later episodes of eruptive volcanism continued sporadically
beginning with extrusions of cooler, crystal-rich moat rhyolite at 200,000 year intervals (500,000, 300,000, and
100,000 years ago) in clockwise succession around the resurgent dome. Some of this extruded magma formed
rhyolite domes and flows and the hills northwest of Hot Creek are domes that formed in this way. The most
recent episode of volcanism in the caldera originated from the Mono-Inyo craters about 500-600 years ago.
Shortly after the eruption, a large lake formed in the remaining caldera depression. Doming of the caldera
floor, combined with continual seasonal inflow of water from the nearby mountains, gradually raised the lake’s
water level. Eventually the water level reached the lake’s southeastern margin, the lowest point in the caldera
rim, and spilled over, carving the deep channel of the Owens River gorge. Once the lake began overflowing, the
river probably cut quite rapidly into the easily eroded Bishop Tuff. After the spillway eroded deeply enough to
drain the lake, the Owens River lost its main water supply. It’s flow has since fluctuated, increasing during the
wet years of the ice age, decreasing during the drier periods between periods of glacial advance. Lake Crowley, a
DWP reservoir impounded behind a small dam at the head of the gorge, dates back only to 1941, whereas the
ancient lake whose site it occupies may have drained as long ago as 100,000 years. Lake Crowley gathers the
water of the upper Owens River as well as the water diverted by a DWP aqueduct into the upper Owens River,
from four of the streams that normally flow into Mono Lake.
Subsurface activity in the Caldera was recently renewed when a resurgent dome began to form in 19781980 as continuously intruding magma lifted the center of the Caldera by about 2.5 feet (by 2000) and a host of
earthquake swarms were recorded by measuring instruments. The first earthquake in the series occurred in 1978
with a magnitude of 5.4 on the seismometer while in 1980 there were four earthquakes that measured over 6.0.
Earthquake swarms have been on-going ever since although none have exceeded 4.5 in recent years and their
frequency and number have decreased dramatically since 2000.
Abundant evidence gathered by many scientists indicates that a major magma body may exist between 3 to
4.5 miles beneath the central part of the caldera and in the late 1980s scientists initiated investigations to
determine the feasibility of extracting geothermal energy from residual magma. Large magma bodies insulated
within the Earth’s crust such as the one beneath the Long Valley caldera, have a very slow cooling rate and can
retain significant amounts of heat for hundreds of thousands of years. Seismic, geological and geophysical data
indicate that a major shallow magma body may exist beneath the Long Valley caldera as does as an extensive and
very active hydrothermal system including hot springs, fumaroles, and areas of active hydrothermal alteration.
The heat source for these features is presumably from a residual magma chamber beneath the resurgent dome.
With few exceptions, however, drill holes show that hot water is confined to relatively shallow aquifers that are
less than 2,300 feet deep and does not substantially increase in temperature with depth.
THE VOLCANIC TABLELAND AND BISHOP TUFF
The Volcanic Tableland and Bishop Tuff is derived from the Long Valley caldera explosion that occurred
760,000 +/- 4,000 B.P. The Volcanic Tableland is comprised of the ash and other fragmental debris that was
ejected at the time of the Long Valley colossal eruption and is known as the Bishop Tuff. The volume of the
Bishop Tuff is about 150 cubic miles, enough to cover all of Los Angeles County to a depth of 200 feet. No
volcanic eruption in all of recorded human history has even remotely approached that size. By comparison, the
eruption that formed the Long Valley caldera was 500 times larger than the 1980 eruption that blew the top off
Mt. St. Helens. The Bishop Tuff material originally blanketed 600 square miles between Bishop and Mono
Lake. Since the 760,000 B.P. eruption, portions of the tuff have been eroded away or buried by glacial
debris left behind by retreating glaciers or overlain by extrusive volcanic material ejected during
subsequent eruptive events. As the northern Owens Valley has widened by faulting, the Bishop Tuff has been
stretched considerably in the past 700,000 years.
The tuff erupted as an effervescing froth of lava that was torn apart by internal gas pressure. When it
came to rest, it was a hot, plastic, porous mass. The weight of the overlying material, coupled with residual heat,
compressed the deeper layers into a dense mass, re-melting some of the globs of pumice, flattening others, and
turning them black. This process is known as welding and the resulting rock is a welded tuff. These dynamics are
reflected in the changing appearance and density of the tuff with increasing depth. In the upper section of the tuff
formation, the rock is glassy and porous, a pale gray or salmon colored rock that consists of chunks of pumice, or
volcanic foam. Deposits like this form when gas-rich magma blows out of the earth, filling the air with blobs of
molten volcanic glass. Trapped gases expand the blobs into bubbly little sponges of pumice which are extremely
porous and light weight because of all the air space created by the bubbles before they cool and burst. A close
look at the pumice reveals small crystals scattered through the glass foam. Clear ones are quartz and feldspar,
and black specs are biotite, an iron-rich mica. Also to be seen are small bits of older rock that were caught up in
the magma as it erupted.
Lower in the tuff formation, the tuff becomes less porous, with blobs of pale pumice, ranging from a few
tenths of an inch to over an inch in diameter in a pink matrix. Still lower in the tuff formation, pumice clots
merge into flattened dark pink streaks that lie above a uniform dark gray tuff where pumice clots become almost
non-existent. The bubbles have been completely flattened and the tuff has lost its porosity.
Conical mounds, typically 10-100 feet high and dotting the surface of the Volcanic Tableland, mark the sites
of old steam vents, called fumaroles, through which volcanic gases escaped. These fossil fumeroles stand high on
the present surface because the gases that streamed through them deposited minerals that cemented the tuff,
making it more resistant to erosion than un-cemented tuff in the poorly welded upper part of the deposit.
HOT CREEK: A SURFACE EXPRESSION OF GEOTHERMAL ACTIVITY
Hot Creek, a public hot springs sited along the lower Mammoth Creek channel southeast of Mammoth
Lakes in the Long Valley Caldera, is an example of geothermal phenomena exposed at the earth’s surface.
Hot Creek originates high in the Sierra Nevada in the Mammoth Lakes basin as Mammoth Creek. Derived
from snow melt and the drop of the Twin Falls and flow of the Twin Lakes outlet, Mammoth Creek flows
southeastward through the Mammoth embayment toward Highway #395; East of Highway #395, the name of this
stream changes to Hot Creek and about three miles east of Highway #395 and about halfway between Mammoth
Lakes and Crowley Lake, the hot springs and steam vents at the Hot Creek site are encountered. These
geothermal features owe their existence to the presence of remnant magma about 10,000 feet below the surface,
the vestiges of the great magma chamber from which the Bishop tuff erupted 760,000 years ago.
The Hot Creek flows through a late-Pleistocene gorge carved deeply into the post-caldera rhyolite flows
and underlying Bishop Tuff by glacial melt water. The walls of the gorge are volcanic, chiefly rhyolite,
that have been much altered by hot water and volcanic gases, mostly steam and carbon dioxide along with
small concentrations of sulfur compounds. Sulfur oxide gases combine with water to form sulfuric acid, which
is highly corrosive to rocks, vegetation and geothermal pipes. Acid attack has left much of the rock around Hot
Creek bleached and largely converted to clay. Not all the rock, however, has been completely altered; in places
there are remnants of volcanic glass, obsidian, complete with flow banding.
Within the gorge, on both sides of the Hot Creek are a series of fumaroles, volcanic-gas vents that emit fumes
or vapors, and hot springs that have surrounded themselves with deposits of siliceous sinter, a rock made of a
form of silica similar to opal, and travertine, a banded form of calcite (calcium carbonate). Sinter and travertine
form when these substances come out of solution in hot water as it ascends, cools and loses its gases. White
sinter and travertine abound along the upper part of the Hot Creek trail marking sites of extinct hot springs. Partway down the trail are a group of vigorously steaming fumaroles that appeared abruptly during the night of
August 24, 1973, about 12 hours before the occurrence of a small local earthquake. Two small geysers and
several smaller vents also formed here at that time, temporarily spouting steam, mud and hot water. Other new
vents formed on the north side of the creek during the four earthquakes (magnitude 6.0) of May 25-27, 1980 that
were centered a few miles west of Hot Creek. Clearly, earthquakes can and do alter the alignment and pressure
conditions within the fissures and venting system below the surface in the Hot Creek area.
At the bottom of the gorge, under the stream-water at the bed of the Hot Creek itself, several hot
springs rise to contribute hot water to be mixed with the Mammoth Creek cold water arriving from the
snow melt and runoff from the Sierra Nevada’s Mammoth Lakes Basin. The surface level of the Hot Creek
varies by several feet from season to season. It is highest in spring, when snowmelt is high, and lowest in fall.
The spring addition of more cold water dilutes the hot water arriving from the vents on the floor of Hot Creek and
reduces water temperatures in the Creek. In the season of lower runoff, water temperatures at the spring sites can
be much warmer. The water surface often displays bubble trails as volcanic gases from vents on the creek floor
rise to the surface. Moreover, a deep rhythmic thumping can be felt at the floor of the creek, probably the result
of gas bubbles collapsing in the fissures and vents below. The hot water springs of Hot Creek have been in
existence for about 300,000 years and the chemical compounds contributed by the springs found their way into
the Owens River and Owens Lake, and in Ice Age times when Owens Lake overflowed southward, into China
and Searles Lake basins. The minerals concentrated in these lakes formed the salts and brines that have been
mined on the dry floors of these lakes beds in recent times for a variety of saline products including borax, potash
and soda ash.
INYO DOMES CHAIN
The area around the Town of Mammoth Lakes, much of it within the Inyo National Forest, contains some of
the youngest and most interesting volcanic features in the United States. Among these volcanic features is a
chain of lava domes, craters, fissures and fractures that run north-south between June Lake and Mammoth
Mountain known as the Inyo Domes Chain. Eruptions in this chain last occurred around 600 years ago and
although the lava and tephra has cooled and the forest around them has recovered, very little weathering and
erosional change has occurred among the landform features left behind by the eruptive events.
Variations in Volcanic Eruptions
Volcanic activity is the process of molten rock flowing toward the earth’s surface and escaping to flow onto
the surface or to be ejected into the air above a surface vent followed by a fall back to the surface at varying
distances from the vent. Small differences in this relatively simple process produces an amazing variety of
eruptive features and formations. Four general types of volcanic activity can be recognized in the distinctive
formations of the Inyo Domes Chain; 1) Air Fall Tephra Eruption, 2) Ash Flow Eruption, 3) Lava Eruption, 4)
Phreatic Eruption.
Extrusive Igneous Features Associated with the Inyo Domes Chain
When magma began rising beneath the southern end of the Mono-Inyo Craters volcanic chain about 5-600
years ago it did so in the form of a six mile long (and 40 feet wide) north-south trending dike that fed eruptions to
form the Inyo lava flows and craters, several explosion craters around Deer Mountain and the Deadman, Glass
Creek and Obsidian Dome flows. Wilson’s Butte (a volcanic dome), almost two miles north of Obsidian Dome,
dates from about 1300 BP and although not connected to the Inyo Domes Chain dike, was formed by rhyolitic
material from the same fracture zone. The Glass Creek and Obsidian Domes and Wilson’s Butte are just north of
the Long Valley Caldera’s northwestern rim.
Inyo Craters
Located just north of Mammoth Mountain and within the western reach of Long Valley, the Inyo Craters are
a series of three domes, including Deer Mountain, with phreatic blast pit craters sited near the southern end of
the south to north chain of young volcanoes that reach northward to Mono Lake. The Inyo Craters (North and
South Craters) and North Dear Mountain were formed by eruptions of low-silica rhyolite beginning 5,000 BP.
The most recent eruptive activity (500-600 BP), was phreatic in origin and created sizeable blast pit craters and
pumice/ash tephra deposits as much as 7.5 miles miles away from the centers of the craters.
The Inyo Craters are among the most striking structures formed by the Inyo eruptions about 5-600 years ago.
The craters are about 1,950 feet in diameter and 195 feet deep. These and several other explosion craters (blast
pits) nearby were formed by steam-driven (phreatic) explosions that ejected solid rock fragments into the air,
some more than 3.5 feet in diameter. The explosions occurred as groundwater was heated by magma rising
toward the surface. When the hot water reached boiling temperature or as the water pressure suddenly dropped
(for example, during an earthquake caused by the rising magma), sudden explosions fractured the surrounding
rock and blasted debris into the air and onto the ground. The lakes at the bottom of the craters were formed from
snowmelt and rainwater. The greenish color of the water reflects the presence of algae organisms.
Deadman Flow
North of Dear Mountain, a series of steam driven explosions erupted from a vent located beneath the South
Deadman flow. This early activity was followed by much stronger explosive eruptions at the South Deadman
vent, which ejected molten rock as pumice and ash fragments during at least two separate episodes. This early
activity also generated a pyroclastic flow that spread almost 4 miles from the vent. Soon after this eruptive
activity at South Deadmen vent, explosive eruptions began at Obsidian vent and then at the Glass Creek vent,
located three and 2 miles to the north, respectively. Finally, a series of steam-driven eruptions along the Inyo
Chain ended the explosive phase of the eruptive activity.
During the first explosive episode of the Deadman eruptions, the prevailing wind was blowing toward the
northeast. Pumice and ash rising in the eruption column were blown northeast and then fell to ground to form a
layer that is more than 4 feet thick near the vent and about 6 inches thick at a distance of about 7 miles. A
second explosive episode erupted a series of pyroclastic flows that extend at least 4 miles to the northeast and
over a mile to the west. The pyroclastic-flow deposits are more than 6 feet thick near the vent along Deadman
Creek. During a third explosive episode, the prevailing wind carried tephra toward the south-southwest. This
eruptive event produced about 4 times more tephra blowin into the air than the first one. Near the vent the
resulting tephra deposit is more than 13 feet thick. At a distance of 7 miles from the vent, the deposit is about 1
foot deep.
Obsidian Dome and Flow
Volcanologists have learned much about the Inyo Dome Chain eruptions from surface geologic observations
and from three research holes drilled in 1983 and 1984 on and near Obsidian Dome, the largest of the Inyo
Domes. The cause of the eruption was the slow ascent of the magma dike from a chamber located many miles
below the surface. As the earth’s crust fractured and pulled apart to accommodate the rising dike, jets of steam
began escaping tossing blocks of rock high into the air and excavating craters around 600 B.P. At three of the
craters the steam explosions soon turned to more violet air-fall tephra eruptions with temperatures of 15000 to
16000 F. and upward velocities of 300-1,000 feet per second. Blocks of magma and granite, larger and in some
cases heavier than bowling balls, were ejected with such force that they reached altitudes of thousands of feet.
Columns of ash rose more than 30,000 feet into the atmosphere above the vents and an ash flow swept eastward
to the vicinity of what is now Highway #395. The explosive eruptions gradually subsided as the rising magma
lost more and more gas. After a shortish time, perhaps a few days, all the explosive activity stopped.
At the three main vents, the explosions had excavated great funnel-shaped holes (blast pits) more that 1,000
feet deep and partly or completely filled with hot ash. Magma continued to rise from the dike into these vents,
but now the gas escaped without breaking the magma into a spray. Great volumes of magma oozed outward onto
the surface and the lava piled up near the vents to form domes. The hot, pumice-covered ground shook as
glowing red, 150 feet high walls of lava repeatedly advanced, steepened, and collapsed in avalanches of blocks,
some as big as houses. This activity probably occurred for several months and the piles of blocks that can be seen
today at the edge of the lava domes are more from the last collapse of the hot advancing flow than from
weathering after the eruptions.
Glass Creek Flow
The largest and final magmatic explosive activity of the Inyo Chain eruptions occurred at the Glass Creek
Vent, located between Obsidian and South Deadman vents. Wind carried tephra from the Glass Creek eruption
column toward the south-southwest. Near the vent the resulting deposit is about 5 feet thick and at a distance of 7
miles from the vent, the deposit is more than 50 inches thick.
JUNE LAKE BASIN
The June Lake Basin (also known as Horseshoe Canyon) was formed by glaciers that advanced
northward and northeastward from the Sierra Nevada during Pleistocene times to carve two, connected,
horseshoe shaped, U-shaped troughs. Larger glaciers from early glacial epics flowed out of both of
Horseshoe Canyon’s northern openings and around both sides of the Aeolian Buttes well into the Mono
Basin. Smaller glaciers from later glacial epics only reached to the foot of the Aeolian Buttes.
Repeated glacial advances through Horseshoe Canyon carved the valleys deeper and wider; today, the
lowest depressions in the two troughs are occupied by four lakes, June, Gull, Silver and Grant. Oh Ridge,
a moraine enclosing the northeastern shore of June Lake, is the site of a scenic overlook with a view
southwestward to Carson Peak (10,909’) the massive mountain in the Sierra Nevada that rises in the
distance to the southwest of June Lake. Mountain glacial erosion landforms such as horns, cirques, aretes,
deep U-shaped troughs (valleys) and hanging valleys are visible from the Oh Ridge viewpoint. Oh Ridge,
itself, is partly comprised of a recessional glacial moraine while the crest of a massive right lateral moraine
of Wisconsinian age (45,000 to 75,000 B.P.) extends over one mile in length from Oh Ridge northeastward
to Highway #395 along the east side of, and parallel to, the June Lake Road and path of glacial advance
into the Mono Basin as far as the Aeolian Buttes (topped by Bishop Tuff). Ground moraine and low
recessional moraines and ground moraine are encountered between the Oh Ridge viewpoint and Highway
#395.
June Lake (7,616’) drains westward towards the Sierra Nevada, an unusual situation because streams usually
flow away from mountains. Named Reverse Creek, the stream enters Gull Lake, departs Gull Lake to flow
further west, turn north and enter Silver Lake. From Silver Lake, water flows north via Rush Creek into Grant
Lake, a DWP reservoir that receives water diverted from Lee Vining, Walker and Parker Creeks. Lee Vining,
Walker, Parker and Rush Creeks along with Mill Creek, the northern most but undiverted Sierra stream
flowing to Mono Lake, historically were the primary sources of water that maintained the volume and
level of Mono Lake before the diversion of the four southern-most of these streams to the Grant Lake
Reservoir. From Grant Lake, a DWP constructed tunnel-aqueduct conveys Mono Basin water from these
four creeks under the Mono Craters and into the upper most reaches of the Owens River.
Parker Creek originates in Parker canyon, a classic U-shaped glacially carved and deepened valley. At the
close of the Pleistocene, the advancing glacier of Parker Valley built an immense terminal moraine that remains
whole and perfect, the only such terminal moraine in the region unspoiled by subsequent erosion. In Parker
Canyon, the post-Pleistocene drainage channel was cut through a lateral moraine, leaving the terminal moraine
unchanged.
The June Lakes Basalt Flow erupted from the former June Lake Volcano located ½ mile along June Lake
Road southwest of #395. The volcano was active between the last two glacial epics, Tenaya and Tioga, between
20,000 BP and 26,000 BP. Basalt poured northward from June Lake Volcano and flowed around the eastern
flank of the Aeolian Buttes and continued northward for almost three miles before its advance was halted. The
later flow of South Coulee in the Mono Craters Range spilled into the glacial basin east of the Aeoloian Buttes
covering a portion of the lava flow derived earlier from June Lake Volcano. The northward advance of the June
Lake glacier during the Tioga glacial epic caused the ice to climb over the volcano’s southern face; the glacier’s
continued advance north into the volcano’s crater eroded away the entire northern half of the volcano’s slopes.
GLACIAL STRATIGRAPHY
Extensive mountain glaciation occurred in the Sierra Nevada Mountains during the Pleistocene era and gave
rise to numerous erosional and depositional landforms at various elevations and occurred as far south as Olancha
Peak. The major periods of glacial advance and retreat in the Sierra Nevada Mountains can be loosely
correlated with the great advances and retreats of the massive North American continental glacier farther
north and east.
North America Continental
Glaciation Epoch
Sierra Nevada Glaciation
Epoch
Eastern Slope Till
Wisconsin
Tioga
Tenaya I
Tahoe II
Casa Diablo
about 11-21,000 B.P.
about 24,000-30,000 B.P.
about 60-75,000 B.P.
about 72,000 B.P.
Illinoian
Mono Basin
about 90-120,000 B.P.
Tahoe I/Hobart
about 260,000-440,000 B.P.
Kansan
Reds Meadow
550,000-700,000 B.P.
Long Valley
700,000 B.P.
Nebraskan
Sherwin
730,000-900,000 B.P.
Pre-Nebraskan
McGee
older than 1,600,000 M.Y. B. P.
Late Pliocene
Deadman Pass
between 2.7 M. Y. B. P.
and 3.1 M. Y. B. P.
Glacially Generated Landforms in the Sierra Nevada Mountains Viewed From Panum Crater
At the base of the western slopes of the Mono Basin, the steep, eastern face of the Sierra Nevada rises
abruptly and impressively while displaying the impact of successive ice age epochs in Wisconsin and Illinoisan
times. The view westward from Panum Crater in the Mono Basin reveals the horn of Mt. Dana rising between
Gibbs and Lee Vining Canyons while the horns of Banner and Ritter mountains can be identified in the distance
to the southwest. U-shaped troughs carved by glaciers advancing down former stream valleys open onto the more
gentle slopes of Mono Basin. Viewed from Panum Crater, from north to south, are arrayed Lee Vining Canyon,
Gibbs Canyon, Bloody Canyon and Parker Canyon, all glacially carved U-shaped valleys. At the foot of Bloody
Canyon, relatively young lateral (and terminal?) moraines were built during the Tahoe, Tenaya and Tioga
advances/retreats while to their south are older moraines created during the Mono Basin glacial epoch. The
moraines at Bloody Canyon consist of a large pair of parallel lateral moraines that were created during the Tahoe
advance/retreat while nested within them are moraines from the subsequent and less expansive, most recent
glacial epochs, the Tioga and Tenaya.
MONO CRATERS
The Mono and Inyo craters and the volcanoes of Mono Lake constitute a chain of late Quaternary
silicic volcanic edifices that extends 25 miles northward along the eastern frontal faults of the Sierra
Nevada from the Long Valley Caldera to Mono Lake. Most of these volcanic domes, flows and craters
appear to be less than about 40,000 years old. These landforms and associated pyroclastic flow and fall
deposits that blanket the region represent more than two dozen major silicic eruptive episodes and the
chain can be regarded as one of the most active volcanic sources in the western United States.
Located at the southern edge of the Mono Basin, the misnamed Mono Craters are properly a complex
of twenty-one, recently formed, abutting and overlapping rhyolite domes, explosion pit craters and coulees
(stubby flows). Aligned on a 10.5 mile long, north south axis of crustal weakness, the Mono Craters
complex constitutes an arcuate assemblage of igneous extrusive features and material of late Pleistocene
and Holocene age. Much of the Mono Crater complex was formed between 9,000 and 12,000 B. P. and can
be identified as the youngest mountain range in North America. Indeed, radiocarbon analyses indicates
that the two most recent eruptive episodes within this volcanic chain occurred in about 705 and 1395 +/- 50
A.D.
Stratigraphic and sedimentologic studies reveal that the products of the most recent eruptive episode
emanated from several aligned vents along the crest of the northernmost three miles of the volcanic chain. The
oldest products of these eruptions are several plinian to subplinian tephras. These tephras are overlain locally by
pyroclastic flow and surge deposits. Tephra refers to all the pyroclastic material thrown into the air above a
volcano and tephra particles can range in size from fine dust and ash to lava fragments many tens of feet in
diameter. Tephra rings, domes and coulees were constructed near the vents during the waning stages of the
eruption sequence. The highest dome measures 2,595 feet above the surface of Mono Lake. Panum (or North
Crater), its rim 630 feet above the level of Mono Lake, is the northern most and youngest of the extrusive features
having been formed around 1300 A. D. North Coulee's two domes average 1,902' in height and were formed
around 1800 B. P.
The most recently formed domes and flows of the Mono Craters appear to plug the vents of most of the
latest Quaternary eruptions. Most of these domes are formed of a light gray, highly silicious rock called
rhyolite which is lighter weight than basalt, owing partly to its sponge-like texture. Although markedly
similar in its bulk chemistry and trace element chemistry, some of the rhyolite rocks look much like solidified
froth, while others are solid glass ranging in color from light to dark gray. Some of the glass is black and is
called obsidian. Including such a dark rock as obsidian in the light-colored group may seem inconsistent
yet obsidian is typically associated with light-colored volcanic rocks and is similar to them in chemical
composition; it does not occur with the dark-colored rocks such as basalt. Texturally, the rocks are much
more variable. The domes, flows and pyroclastic deposits that erupted prior to about 2,000 years ago, are
porphyritic glassy rhyolites, whereas younger erupted products are aphyric or very sparsely porphyritic. Most of
the aphyric rhyolitic domes and flows (Panum Dome, Cratered Dome, Upper Dome, North Coulee and South
Coulee) are not mantled by pyroclastic flow or fall deposits. All the other domes and flows are thickly mantled
with pyroclastic debris.
Unlike basaltic lava, which flows readily from it’s vent, rhyolitic lava is extremely viscous and is often
semi-plastic or solid by the time it emerges at the surface, thus readily plugging its vent much like a cork.
This plugging allows gas pressure below to build which may be relieved by violent explosions resulting in
showers of pea- to walnut-size pumice fragments and fine ash that may blanket the countryside for miles.
Pumice, found almost everywhere in the region, resembles the frothy rhyolite seen in some of the large blocks
around the dome’s base, although it is generally lighter weight and will even float for a time on water. During the
active life of a rhyolitic volcano, the viscous lava may become sufficiently fluid to flow sluggishly for short
distances. The formation of domes often marks the last activity of rhyolite volcanoes although sometimes domes
succeed each other, the new one destroying the older one by violent explosions. The explosions frequently
develop large craters within which a new dome may arise such as at Panum Crater, the northern most of
the Mono Craters.
Excluding Mammoth Mountain at the south end of the alignment chain, which is older, all of these
domes erupted over a period of about 40,000 years, most of them during the last 10,000 years. The two
youngest erupted about 700 and 1400 A.D. and one small flow on Negit Island in Mono Lake may be as
young as the late 1700s A.D. Their chemical composition is so similar, that together with their alignment,
it is logical to conclude that they probably all came from a common subterranean magma chamber. Their
remarkable alignment suggests that a large fracture or a narrow zone of fractures, provided channels
through which the fluid rock reached the earth’s surface.
Panum Dune and Dune Field
Panum Dome, itself, and its associated tephra ring (the circular rim that seems to define Panum
Crater), are very late and relatively passively erupted products of the latest eruption of the Mono Craters
(1300 A.D). The tephra ring, which rises as much as 195 feet above the surrounding plain, rests upon the latest
pyroclastic flow deposits that emanated from the Panum vent. Panum Dome is composed of four structurally and
texturally distinct domes, the largest and youngest of which is called North Dome. This dome consists of a light
gray banded rhyolite surrounded by a collar of breadcrusted light gray pumiceous rhyolite and is bisected by a
north-south fissure. A slightly older and much smaller feature, South Dome, lies south of and is intruded by
North Dome. The dome is cored by banded rhyolite and has a 32.5 feet-thick crust of concentrically foliated
pumice topped by a discontinuous shell of black structureless obsidian.
Within a quarter-mile radius of Panum Dome, a “throat clearing breccia” overlies an airfall tephra and ranges
up to seven feet in thickness. Overlying the breccia near the vent is a white to pale pink pumiceous pyroclastic
flow bed of quite variable thickness. In excavations sited about 3/4 of a mile and one mile southwest of Panum
Dome, this pebbly, cobbly bed forms twenty inches-high pebbly dunes aligned northwest-southeast. Although
white, pumiceous pyroclastic flow deposits are present in all directions away from Panum Dome, for some reason
dunes are apparent only in the southwestern quadrant. In this dune field, amplitude of the dunes ranges to about
39 inches and wave length varies from about 32 to about 320 feet. Slope angles of 20-25 degrees are common.
The dunes appear to be concentrically aligned around a point about 3200 feet south of the center of Panum Dome,
and Panum vent beneath Panum Dome, is the source of the dunes’ material. The pyroclasts of the dune bed must
have been “bed load” at the base of a very hot radially expanding, southwesterly moving cloud.
MONO BASIN AND MONO LAKE
"Mono" is the Yokut Indian word for "brine or alkali fly" and "fly people." The Yokuts, who dwell in the
Yosemite region, considered the flies of Mono Lake to be a delicacy.
GLACIAL LAKE RUSSELL
Mono Basin is one of the 100 independent intermontane basins comprising the basin and range
topography of the landscape between the Sierra Nevada-Cascades alignment and the Rocky Mountains.
The floor of Mono Basin has been subsiding for the past 3 to 4 million years, dropping a total of 6,000 feet,
and is half filled with sediment washed down from the surrounding uplands.
Mono Lake occupies the bottom of the basin which has been inundated by a lake since mid-Pleistocene
times, at least since 730,000 B. P. In Ice Age times, glacial Mono Lake, also known as Lake Russell,
(named after the 19th century geologist Israel C. Russell who visited Mono Basin in the late 1870s and
early 1880s and studied the regional geology) inundated a large portion of Mono Basin. At its greatest
extent, the lake covered 338 square miles, was 28 miles long by 18 miles wide, and reached a depth of about
900 feet (five times larger than the present lake). During the height of the glaciation, the lake surface was
approximately 400 feet above its present level, about as high as the present town of Lee Vining. Glacial
Lake Russell probably filled its basin only during the warmer, centuries long interglacial periods, when
glaciers were melting back up the mountain canyons. There were at least seven major glacial advances
and six interglacial retreats during the last one million years of the Pleistocene Era.
Ancient shore lines and wave incised lake beach terraces on the slopes of the surrounding hills and
mountains testify to the existence of the massive former glacial Lake Russell and to the abundant runoff
from huge glaciers that fed the streams and rivers flowing into the lake. Indeed, at the height of the
Pleistocene when neighboring glaciers were over 500 feet high and advanced farthest down slope beyond
their canyons, the lower faces of the glaciers occupying Rush, Bloody, Lee Vining and Lundy canyons were
in contact with Lake Russell. Precipitation was four or five times greater in Pleistocene times in the Mono
Basin compared to today. About 13,000 B. P. when glacial Lake Russell was most extensive, water spilled out
of the eastern edge of the Mono Basin and flowed southward and eastward into the Adobe Valley and beyond and
supplied water to other lakes in other basins.
About 12,000 B. P. the ice age ended and the Pleistocene era transitioned into the Holocene. The glaciers
retreated or disappeared, runoff was dramatically diminished and the level of Lake Russell fell. When the first
European visitors encountered the Basin in the last century, Mono Lake existed as a smaller remnant of the
former much larger Lake Russell. In 1857, when Mono Lake's shores were first surveyed, the lake's level was
6,407 feet. During the following 70 years, a preponderance of wet winters raised the lake to 6,428 feet in 1919.
The dry 1930’s brought the level down ten feet to 6,418 feet.
MONO LAKE
Mono Basin lies in the rain shadow of the Sierra Nevada Mountains. Precipitation in the basin is
minimal, a desert climate characterizes its location and every year three and a half feet of water, or
140,000 acre feet, evaporate from Mono Lake's surface. Until 1941, the existence of Mono Lake was
heavily dependent on six streams that drain the eastern slopes of the Sierra Nevadas and provided 65%75% of the lake's annual water supply. These streams, from south to north, were Rush Creek, Parker
Creek, Walker Creek, Lee Vining Creek, Mill Creek and Wilson Creek. Diversion of the four southern
most creeks to the Owens Valley in 1941, left only Mill and Wilson Creeks to supply Sierra Nevada stream
runoff to the lake until 1989 when diversions from the four southern streams were halted. Currently,
Mono Lake is eight miles across from north to south, thirteen miles across from east to west
and its circular shape extends over about 63 square miles. Averaging fifty feet in depth, the greatest depth
of Mono Lake is 150 feet near the south side of Paoha Island. No other natural lake entirely within
California holds a greater volume of water.
Having no outlet, Mono Lake loses a substantial volume of its water every year to evaporation. Since
the last time Mono Lake was high enough to overflow its basin, approximately 60,000 BP during the Tahoe
Glacial epic (three ice ages ago), the mineral content of the lake water has steadily increased until the
saline density level has reached over nine percent (Lake Tahoe is .001%, the ocean is 3.5% and Great Salt
Lake is 18%) and the water is eighty times as alkaline as sea water. Water percolating down through the low
grade marble and metamorphic limestone walls of Lundy Canyon, together with springs and other streams
account for the high mineral content level. Over 280 million tons of salts are dissolved in the waters of Mono
Lake. In terms of chemical composition, Mono Lake differs from the Great Salt Lake and most other saline lakes.
Sodium salts of chlorides, carbonates and sulfates dominate its waters. Sea water, by comparison, is richer in
chloride but poorer in sulfate and carbonate. So is Great Salt Lake which contains ten times more chloride but
no carbonate. Mono Lake is also exceptionally rich in borate and potassium. These chemical conditions
largely determine what can live in the lake. In sum, Mono is a salty, soda, sulfurous lake, or as scientists
would say, a chloro-carbonate-sulfate or triple water lake.
MONO LAKE ECOSYSTEM
Although the high level of lake water salinity precludes the existence of most forms of life, a few species
exist in astronomical numbers. The food chain begins with microscopic green algae which uses decayed
organic matter and sunlight to grow. In summer when the algae blooms, the lake may become pea soup
green. Two animals feast on the algae, brine shrimp (Artemia monica) and brine flies (Ephydra). Brine
shrimp have evolved as a unique species in these waters and can be seen in the trillions in the height of the
summer season which occurs from April through October. As winter approaches, the adult brine shrimp begin to
die off, but not before eggs are laid that will spend the winter in the lake-bottom mud. The eggs hatch out as the
lake water warms in the spring. These brine shrimp crustaceans exist in such massive quantities that in summer
at peak densities, over 50,000 brine shrimp crowd a cubic yard of lake water and there are over 4 trillion
individuals in the lake. Some 250 tons (over 20 billion individuals) are commercially harvested each summer,
packaged and marketed around the world to be used as fish food. A brine shrimp processing plant is located
north of Lee Vining near the shore of the lake.
Brine fly females can actually walk into the lake in an air bubble and lay their eggs on pieces of rock or tufa.
The egg becomes a larvae and then a pupa before the adult fly finally emerges. The pupa stage of the brine fly
along with brine shrimp were collected by the local Kuzedika Paiute Indians, dried and ground into a protein rich
meal that served as an important food resource and trade item.
Mono Lake's brine shrimp (often forced to the surface by underground springs beneath the lake bed)
and flies provide a plentiful food supply for ninety-eight species of migratory water birds that visit the lake
each spring and summer. The abundance of birds is related to the absence of fish, which can not survive
in the salty lake. Without fish competing for shrimp and flies, the birds enjoy an inexhaustible food
supply. Particularly notable bird species include three migrants: Eared Grebes, Wilson's and Red-necked
Phalaropes, and two nesting species-California Gulls and Snowy Plovers. About 150,000 Phalaropes visit Mono
Lake in July and August and Eared Grebes visit in astonishing numbers (up to 800,000) from August through
October. Snowy Plovers nest along the alkali flats of the lake's eastern shore and this colony of 400 birds
represents about 10% of the California population of this species. About 45,000 adult California Gulls fly to
Mono Lake from the Pacific coast each spring to nest, mostly on Negit Island. Approximately 85% of the
California population of this species is born at Mono Lake.
TUFA TOWERS
Tufa towers are masses of precipitated mineral salts that were formed on the floor of Mono Lake under
water, but now appear as oddly shaped "lithoids" standing on portions of the former lake bed or rising
above the lake surface in shallow locations near the shore line. The chemistry of the lake water, mineral
content of the springs that feed the lake under the lake floor, and certain types of tiny algae combine to create the
tufa towers. Tufa is from the Latin "tofus" meaning "porous stone." The tufa towers are formed at the orifices
of sublacustrine springs as minerals in the spring water (mostly calcium) combine with minerals in the lake
water (mostly carbonates) and precipitate out from their dissolved state and adhere to the rim of the
spring orifice. The continuous accumulation of these mineral precipitates (mostly calcium carbonates and
chemically identical to limestone) around the springs' orifices yield a growth of this material both laterally
and vertically to form the tufa towers upward from the lake floor. Each tufa tower is honeycombed with
tubular pathways through which the spring water passes through the tufa material to reach the orifice where
contact is made with lake water. Over time the tufa deposits accumulate and are sculpted by currents and waves.
A tufa tower only becomes visible above the lake surface when the lake level falls below the tufa tower's
summit. As the lake level continues to drop, the tufa towers nearest the shore may become marooned as
the shoreline recedes below their base. Once the tufa tower is separated from the lake water, no more
growth of the tufa material is possible and the tufa tower exists as a fossilized formerly underwater spring.
The tufa towers at the southern edge of the lake are estimated to be between 200 and 900 years old. Some
tufa towers, as much as 13,000 years old, can be found high above the current lake level along Mono
Lake's ancient shore.
MONO LAKE ISLANDS
Two islands exist in the center of Mono Lake, Negit (the black island) and Paoha (the white island).
Both islands were named by Israel Russell and reflect his romanticism as he applied some of the poetic words
from the languages of the aboriginal inhabitants of the Basin. Paoha is from a Paiute Indian word meaning
"Diminutive Spirits of the Mist" and refers to the hot spring vapors that emanate from geothermal sources at the
eastern end of the island which was formed by both intrusive and extrusive igneous activity. Intrusive igneous
material (or uplift along a fault) rose to force the lake bottom to rise above water level about 325 years ago while
lava reached the surface to flow onto the northern and eastern surface of the island. The most recent eruptive
events on the island occurred about 200 years ago. The white portions of Paoha are made up of twenty feet thick
accumulations of diatomaceous earth, the remains of colonies of millions of one-celled aquatic self-propelled
organisms.
Negit is a Paiute term for "blue winged goose," a reference to the thousands of California Gulls who make the
island their rookery. The seagulls arrive from the Pacific Ocean annually in early May, lay their eggs, hatch their
young and return with their offspring to the ocean before winter comes to the high country. Negit island is the top
of a flattish volcanic cone formed from at least six different eruptions of cinders and lava that occurred mostly
between 1700 B. P. and 300 B. P. One small flow on Negit Islands may be as young as the late 1700’s. The
black cinder surface of the island absorbs the sun's heat which in turn helps hatch the gull eggs to make this warm
protected gull rookery one of the largest in California.
By 1977, Negit Island's California Gull rookery became threatened by the falling lake level. Although
the island was originally two miles off shore, the continuous decline in lake level since 1941, threatened to
yield in 1977 a white, alkali-encrusted land bridge connection between Negit Island and the shore when the
lake level dropped below 6375 feet. The emerging land bridge would form a peninsula which would
provide coyotes, skunks and other predators easy access to the rookery where they could threaten the
nesting California Gulls and their eggs. The gulls could have been forced to abandon the rookery or suffer
a sharp decline in the size of their population. Paoha was not an alternative rookery site because the island is
home to a community of marooned coyotes that prevent gulls from nesting on the island. No satisfactory
explanation exists for how or when the coyotes arrived on the island.
Government officials, concerned for the survival of the rookery, employed the National Guard in early
April, 1979 to blast a moat-like channel around the island in an effort to prevent potential predators from
reaching Negit Island. Conservation organizations argued strenuously that government efforts to protect
the rookery were inadequate and, indeed, coyotes were able to invade the island, rout its estimated 33,000
nesting gulls and preyed on their eggs and chicks. In 1980, despite the erection of a "predator proof"
fence, the gulls did not return. In 1985, after an extremely wet winter, the lake level rose, covering the
land bridge. When Negit became an island again it was re-colonized with 92 gull nests. Each year thereafter
until 1989, the number of nests increased and by 1989 two thirds of the California Gull population was again
nesting on Negit and three of its tiny islets.
Water diversions from the creeks that fed Mono Lake continued even though the late 1980s were
drought years. In August 1989, a Superior Court Judge granted a preliminary injunction ordering the
elevation of Mono Lake to be established at 6,377' above sea level "to prevent irreparable harm to the
ecosystem." The injunction prevented the DWP from diverting water when the lake was below an elevation of
6,377 feet. Water diversions stopped in 1989, however the lengthy California drought of the late 1980s and early
1990s, caused the lake level to continue to drop until it reached a drought low point of 6,373.4' in December
1992. Mono Lake remained below the injunction elevation level of 6,377 feet from 1989 until July 1995 when
the 6377' level was reached again after the very wet winter of 1994-1995. Even though the land bridge was reestablished to Negit Island in November 1990, thus recreating the peninsula and entry for coyotes and other
predators to the island, the California Gull population has increased every year from 1990 through 2000.
Biological studies indicate that Negit and Paoha islets along with Paoha itself seem to be sufficient to support the
increasing gull population.
In Janurary 1995, Negit once again appeared as an island as the rising lake waters inundated the land bridge
following the wet 1994-1995 winter. Biologists have found that the California Gulls re-established their nesting
sites on Negit Island in 1996. Mono Lake has continued to rise and achieved a level of 6,379.6 feet in October
1996 and 6,382 feet in October 1997, 6,384.3 feet in October 1998 and 6,385 feet in July 2000.
According to a DWP estimate, if the diversions of water from the Mono Basin to the city of Los Angeles
had been allowed to continue at the 1970s level (100,000 acre/feet per year), the lake level eventually would
become stabilized at 6,223 feet after the year 2050. Fifty three square miles of barren lake bed would
become exposed by 2050 and the lake surface would shrink by half. A land bridge would connected Negit
and Paoha islands to each other and would appear as a peninsula extending southeastward from the lake
shore.
THE CITY OF LOS ANGELES DIVERSION OF WATER FROM THE MONO BASIN
The Department of Water and Power (DWP) of the city of Los Angeles had developed its Owens Valley
Aqueduct system in the early 20th century in order to bring water from the snow melt of the eastern slopes of the
Sierra Nevada Mountains and the Owens Valley to the City of Los Angeles. In the 1930s the DWP decided to
extend the upper reach of the aqueduct northward to the Sierra Nevada streams that drained into the
Mono Basin and served as the primary source of water for maintaining the level of Mono Lake.
Completed in 1941, the Mono Basin Aqueduct Extension diverted four of the six streams that formerly had
flowed to Mono Lake. A reservoir was constructed in Rush Creek Canyon to form Grant Lake and the
waters of Rush, Parker, Walker and Lee Vining Creeks were redirected into Grant Lake. An 11.5 mile
long tunnel was constructed through and under the Mono Craters and the Mono Aqueduct Extension
conveyed the water stored in Grant Lake out of the Mono Basin to the headwaters of the Owens River. In
1970, a second Owens Valley Aqueduct was completed resulting in a substantial increase in the amount of
water that could be conveyed to Los Angeles. From the 1970s through 1988, about 100,000 acre feet of
water per year was diverted from the Mono Basin to supply about 17% of the water delivered by the DWP
to the City of Los Angeles.
The diversion of 100,000 acre feet per year from the Mono Basin to Los Angeles represented the loss of
50 to 60% of the former volume of water that drained into Mono Lake. After the completion of the 2nd
Owens Valley Aqueduct in 1970, the decline in the lake level proceeded at an average rate of two feet per
year. Deprived of much of its former water supply, Mono Lake's shoreline receded and by 1981, at its
lowest ebb, the lake level had fallen forty five vertical feet and the lake's water had doubled in salinity.
Approximately 30 square miles of lake bottom had been laid bare to the sun and wind and increasing dust
storms frequently violated state and federal air quality standards. A land bridge now connected
MONO LAKE SHORELINE ELEVATION (as measured on October 1)
1850
Shoreline Elevation
6,407 feet
1900
Shoreline Elevation
6,416 feet
1930s
Shoreline Elevation
Ranged from low of 6,415 feet (1934-1937) to high of 6,420
feet in 1930.
1941
Diversion of Mono Basin water begins - 6,417 feet
1950
Shoreline Elevation
6,410 feet
1960
Shoreline Elevation
6,398
1964
Shoreline Elevation
6,391 feet
1970
2nd Owens Valley Aqueduct opened 6388 feet
(total of 100,000 acre feet/year diverted from Mono Basin)
1978
Mono Lake Committee established. Shoreline Elevation
1981
Shoreline Elevation
6,372 feet (lowest lake level in historic times)
1990
Shoreline Elevation
6,375.2 feet
1992
Shoreline Elevation
6,373.7 feet
1994
Shoreline Elevation
6,374.8 feet
1995
Shoreline Elevation
6,377.8 feet
1996
Shoreline Elevation
6,379.7 feet
1997
Shoreline Elevation
6,382.0 feet
1998
Shoreline Elevation
6,384.3 feet
2001
Shoreline Elevation
6,383.8 feet (+9.2 feet since Water Board Decision in 1994)
June 2002 Shoreline Elevation
6,382.8 feet (+8.2 feet since Water Board Decision in 1994)
6,375 feet
Negit Island to the mainland to form a peninsula and the trout fisheries in Rush and Lee Vining creeks
were decimated. In 1982-1983 and 1985-1986, extremely wet winters reversed Mono Lake's decline, but only
temporarily. The lake rose nine vertical feet to an elevation of 6,382 feet. Negit became an island again and the
brine shrimp thrived. Water diversions from the creeks were resumed, however, and the lake level again
declined. By early 1989, the land-bridge to Negit Island was on the verge of surfacing and the California Gull
colony was again threatened. Although water diversions stopped in 1989, the lengthy California drought
caused the lake level to continue to drop. Mono Lake remained below 6,377 feet from 1989 until the
summer of 1995 when a 6,377 foot level was reached after the very wet winter of 1994-1995. During the
drought years of the early 1990s, the lake's elevation reached a drought low point of 6,373.4 feet in
December 1992.
PROTECTION AND RESTORATION OF MONO LAKE AND ITS ECOSYSTEMS
Concerns about change and damage to the lake's ecosystem (particularly the threat to the nesting and
feeding practices of migratory birds), and worries about the effects of wind-blown alkali dust on Mono
Basin air quality, as well as the aesthetic and ethical issues related to a shrinking lake, led to legislation
and litigation in both federal and state courts beginning in the 1970s.
The Mono Lake Tufa State Reserve was created in 1982 and includes the state-owned lake bed lands
below the elevation of 6,417 feet. The drop in lake level of 40 feet since 1941 has exposed as much as 17,000
acres of formerly inundated lake bed. The Reserve is intended to preserve the tufa formations and other
natural features along the shore of Mono Lake.
The Mono Basin National Forest Scenic Area was designated by Congress in 1984 to protect the
natural, cultural and scenic resources of the Mono Basin. The Scenic Area encompasses 116,000 acres and
is the first "Scenic Area" to be so designated in the National Forest System.
LEGAL ISSUES CONCERNING THE LOS ANGELES DWP AND MONO BASIN/LAKE
1. 1923: The Los Angeles Department of Water and Power (LADWP) filed an application with the State Water
Rights Board, predecessor to the State Water Resources Control Board (SWRCB), for permits to divert four
of Mono Lake's tributary streams.
2. 1936: The DWP developed an agreement with SWRCB and California Department of Fish and Game to build
fish hatcheries to compensate for the stream diversions.
3. 1940: The SWRCB granted water permits to DWP to divert water into its Owens Valley Aqueduct system.
4. 1974: The SWRCB granted licenses to DWP confirming Los Angeles's vested rights to divert water from the
Mono Basin streams.
5. 1979: Concerned about the future of Mono Lake, the National Audubon Society, Mono Lake Committee
(founded in 1978), Friends of the Earth and four Mono Basin landowners filed suit to restrict the diversion of
water to Los Angeles.
6. 1983: The California Supreme Court ruled that Los Angeles' water rights need to be redefined in
order to balance the needs of the city with the public trust values of Mono Lake. The Supreme Court
ruled that in granting DWP’s licenses to divert water from Mono Basin streams, the Water Board’s
predecessor had erred by failing to take into account protection of Mono Lake’s public trust values
defined as including “the purity of the air, the scenic views of the lake and it shore, and the use of the
lake for nesting and feed birds.”
7. 1989: A Superior Court Judge granted a preliminary injunction ordering the elevation of Mono Lake at
6,377' above sea level "to prevent irreparable harm to the ecosystem." The injunction prevented the DWP
from diverting water when the lake was below an elevation of 6,377 feet. Water diversions stopped in 1989,
however the lengthy California drought caused the lake level to continue to drop. Mono Lake remained below
the injunction elevation level of 6,377 feet from 1989 through 1994. In December 1992, the lake elevation
reached a drought low point of 6,373.4 feet. The same judge ordered the SWRCB to modify DWP's water right
licenses to balance the needs of Mono Lake with the needs of Los Angeles.
8. 1990: In October, The DWP began preparation of the Mono Basin environmental impact report.
9. December 1992: The DWP halted all diversions of water from the Mono Basin regardless of lake level.
10. June 1993: The Mono Basin draft EIR was completed and circulated for public review. The EIR identified
an elevation of 6,377' as the DWP's proposed future lake level but the DWP was willing to compromise at
6,383.5 feet as a preferred alternative.
11 October 1993 through February 1994: The SWRCB held hearings to gather information and hear
arguments about how to modify DWP water rights licenses to Mono Basin water.
12. September 1994: The SWRCB ruled to restrict the amount of water that Los Angeles could divert
and decided that the future lake level should be set at 6,392 feet (15 feet higher than proposed by the
DWP and comparable to the 1964 lake level); the 6,392 foot lake level was selected principally because
that is the level where air quality violations are predicted to end. At 6,392 feet, the lake's surface area
would be increased from 63 to 76 square miles.
The SWRCB further ruled that broad environmental protection practices be installed to enhance the
Lake and Basin ecosystem. To comply, in August 1995, the DWP submitted a plan to restore the diverted
creeks in Mono Basin, maintain heavy enough flows in the four creeks to support fish populations and
ensure there is sufficient gravel in the stream beds for spawning. Additionally, the DWP must implement
a waterfowl habitat restoration program to compensate for lost wetlands.
The SWRCB estimated that it would take 20 years to raise the lake to its target level of 6,392 feet. If
the lake has not risen to the target level by 2014, the SWRCB will hold another hearing to determine
whether to further revise Los Angeles' water licenses.
During the twenty year refill period (until 2014) when the lake rises to between 6,377 and 6,380 feet, the
DWP can gradually resume taking small amounts of water (4,500 acre feet per year). If the lake rises an
additional eleven feet to a level of 6,391 feet, DWP can increase its diversions to 16,000 acre feet.
Once equilibrium is reached at the target level of 6,391-2 feet, water diversions may be performed
according to the following schedule: If the lake level is less than 6,388 feet, no water may be exported from
the Mono Basin. If the lake level is between 6,388 and 6,391 feet, 10,000 acre feet per year may be
exported. If the lake level exceeds 6,391 feet, 30,000 acre feet of water may be exported. These exports of
water may only occur if fishery flows are first satisfied in the creeks that are targets for diversion.
Websites for Owens valley/ Mammoth earth science
<>Monitoring VolcanicUnrest at Long Valley Caldera, California
...Long Valley Caldera at a Glance.... Long-Term Outlook. Volcano Hazards inarea. USGS
Response Plan. Image Gallery. Additional USGSMonitoring at Long Valley Caldera. ...
<>Description:Real-time data on earthquakes, ground deformation, and volcanic gas.
<>Category:Science > Earth Sciences > Geology > Volcanoes > Observatories
<>Similar pages
<>Geologic History of theLong Valley Caldera
...USGS Long Valley CalderaResponse Plan. ... Color-Code Conditions and AssociatedUSGS
Response Long Valley Caldera andMono-Inyo Craters Region, California. ...
<>Similar pages
[<>More results fromlvo.wr.usgs.gov ]
<>Recent Earthquakes forLong_Valley
LongValley Special Map. Special Map. ---> Please visit ourreorganized earthquake
pages at - http://quake.usgs.gov/ <--- including newCA-NV pages at - http ...
<>Description:Earthquake information for California and Nevada
<>Category:Science > Earth Sciences > ... > Seismicity Reports > United States
<>Similar pages
<>Heat Flow Data for Long_Valley
Logo USGS Heat Flow Data forCalifornia. Long Valley Special Map.
Special Map There are 12 data points on this map. Click on a data...
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[<>More results fromquake.wr.usgs.gov ]
<>CVO Menu -Long Valley - Mammoth - Inyo - MonoVicinity, ...
...Active and Potentially Active Volcanoes in California -- From: Wrightand
Pierson, 1992, USGS Circular 1073, includesLong Valley, Mono and Inyo; ...>
<>Similar pages
<>CVO Website - Visit AVolcano - Long Valley Caldera
...Useful Links. LVO - Long Valley Observatory-- Link courtesy USGS Long Valley
Observatory; Inyo National Forest -- Link courtesy US ForestServicee; ...
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[<>More results fromvulcan.wr.usgs.gov ]
<>Participates in Communication Exercise for LongValley ...
...Dave Hill, Scientist in Charge, USGS LongValley Observatory, The exercise began
when USGS scientist Dave Hill (top) notifed theCalifornia Office of Emegency ...
<>Similar pages
<>Living With a RestlessCaldera, Long Valley, California, Volcano...
...PLANNED USGS RESPONSE TO UNREST IN THE LONGVALLEY AREA. Geologic Behavior. Condition.
USGS Response. ... For further informationvisit the USGS Long Valley website. ...
<>Similar pages
<>Where Will VolcanoesErupt in California's Long Valley Area?,...
...Living With a Restless CalderaóLong Valley,California (USGS Fact Sheet
108-96). ... For further information visit theUSGS Long Valley web site....
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[<>More results fromwrgis.wr.usgs.gov ]
<>The LongValley Caledra and the Mono Inyo Craters
...USGS Long Valley CalderaCurrent Condition page. Forest ... For more details about
USGS's plan see the Long ValleyCaldera Response Plan. Information ...
<>Similar pages
GLOSSARY
OWENS VALLEY - MAMMOTH LAKES - MONO BASIN LANDFORMS AND GEOLOGY
Amphibole: Group name for common rock forming silicate minerals high in iron and magnesium. Any of a
complex group of hydrous silicate minerals containing chiefly calcium, magnesium, sodium, iron and
aluminum and including hornblende. The amphibole mineral family is common in dark-colored igneous
rocks, usually appears dark green or black and may look as if it were lacquered. Amphibole crystals
commonly are long and narrow and commonly show up in granitic rock as brilliant black laths. Amphibole is
similar to pyroxene but breaks (cleaves) at oblique angles (56o and 124o) while pyroxene cleaves at right
angles.
Andesite: A volcanic rock (lava) composed essentially of plagioclase and one or more mafic (magnesium or
iron) constituents. Usually light gray or brown in color. Andesite has a silica content ranging from about 54
to 62 percent and the same chemical composition as diorite. Most minerals are too small to be
distinguished, even with a hand lens. A few crystal of dark minerals may be visible. A rock or chip held to
light is translucent on the edge.
Arete: A sharp rock ridge that separates cirques in alpine landscapes. The arete is an erosional remnant created
by headward erosion of glacial ice in cirques on both sides of the ridge.
Ash: Fine particles of pulverized rock blown from a volcano. Measuring less than about 0.1 inch diameter
(under 1/8 inch or 4mm), ash may be either solid or molten when first erupted. By far the most common
variety is vitric (pertaining to glass) ash, glassy particles formed by gas bubbles bursting through liquid
magma. Lithic ash is formed of older rock pulverized during an explosive eruption, while in crystal ash each
grain is composed of a single crystal or groups of crystals with only traces of glass adhering to them. Many
volcanic ash deposits contain mixtures of all three kinds in various proportions.
Ash Fall: A rain of ash from an eruption cloud.
Bajada: an apron formed of coalescing alluvial fans at the base of a desert mountain range.
Basal Slip: The type of advance of a mountain glacier where the entire glacier, from base to surface, moves as a
unit down slope (in contrast to the movement of upper zones of glacier ice over more deeply buried glacial
ice).
Basalt: An extrusive, dark colored, fine grained lava rock rich in iron and magnesium, relatively poor in silica
(less than 54%), and composed primarily of calcic (containing calcium) plagioclase and pyroxene with or
without olivine. Basalt resembles andesiste, but is usually more nearly black. A chip of basalt held to light is
opaque (unlike andesite which is translucent). Basalt has the same chemical composition as gabbro. The
most common of earth’s volcanic rocks, basaltic lavas compose all the ocean floors and many continental
formations as well. Typically very fluid because of their low silica content, basaltic lavas can flow great
distances from their source, forming broad lava plains and shield volcanoes. Columnar jointing that creates
three to eight sided vertical columns of rock occurs exclusively in basalt, such as at Devil’s Post Pile and the
Little Lake Ranch Basaltic flows south of Fossil Falls, or andesite.
Batholith: Meaning “deep rock,” a batholith is a large mass of granite or adjacent granitic plutons that intruded
rock above and may become exposed at the surface as overlying rock material is eroded away. The Sierra
Nevada Mountain range is often considered to be an uplifted batholith where the granitic rock is widely
exposed at the surface, but older, overlying rock is still present at select locations. The bottom of the
batholith descends toward the earth’s core to an unknown depth.
Bed: The smallest division of a stratified series (strata), marked by a more or less well defined plane that
separates the bed from its neighbors above and below.
Bedding Plane: A more or less well defined plane that separates two strata in a series.
Biotite: A common rock-forming silicate mineral (one of two very common varieties of the mica group of
minerals), occurring in dark black, brown, or green sheets and scales with flexible cleavage plates. Named
after J. B. Biot, an early 19th century mineralogist, biotite is an important constituent of igneous rocks.
Block-and-Ash Flow: Variety of a pyroclastic flow, a turbulent mass of hot dense rock fragments that
avalanches downslope as the result of an eruption. Block-and-ash flows are commonly triggered by the
disruption or collapse of a dome while still hot.
Bomb (Volcanic Bomb): A lump of plastic or molten lava throw out during an explosive eruption. Bombs
range in size from 2.5 inches to many feet in diameter. Because of their plastic condition when first ejected,
bombs are commonly modified in shape during their flight through the air and/or by their impact on the
ground. As the outer crust cools and solidifies, continued expansion of the interior by gas pressure
sometimes causes cracking, which may form a bomb surface resembling the crust of freshly baked bread
(breadcrust bombs).
Breccia: Rock composed of many distinct fragments, typically sharp and/or angular, embedded in a matrix of
fine material. Breccias are sometimes formed when shattered lava blocks are transported by avalanches or
mudflows.
Caldera: The Spanish word for cauldron used to denote a large basin-shaped volcanic depression---by definition
at least a mile in diameter. Calderas are usually found at the top of volcanic cones and are caused by the
collapse of a former summit. Unlike craters, calderas are always formed by collapse.
Cinders: General term applied to vesicular (full of cavities--a vesicle is a cavity in a rock due to the former
presence of gas or vapor) rock fragments ejected during explosive eruptions. Volcanic cinders are like
volcanic ash but coarser, 1/8 to 1 inch in diameter (pebble size). Cinders are usually red or black (red results
from oxidation—the rusting of iron).
Cinder Cone: A volcanic cone built entirely of tephra and/or other pyroclastic material, commonly by the mildly
explosive ejection of semi-fluid or plastic lava fragments. Most cinder cones are relatively small steep-sided
structures built during a single eruptive episode. Cinder-cones commonly discharge lava flows from vents at
the base of the cone.
Cirque: An amphitheater-like depression in alpine regions, formed by the plucking action of glacial ice. These
large semi-circular basins have been carved into the upper slopes of many Sierra Nevada peaks. Found at the
head of a glaciated valley, a cirque is one of various glacial erosional landforms that commonly occur in
mountain source regions of glaciers.
Col: A low saddle in a glacially carved ridge between two cirques.
Composite Cone: Another term for a stratovolcano, a large volcanic cone constructed of both lava flows and
pyroclastic material.
Conduit: The feeding pipe of a volcano, the “throat” through which magma passes on its way to the Earth’s
surface.
Coolee: A short, stubby, steep-fronted lava flow, usually of rhyolitic composition.
Crater: The bowl or funnel-shaped hollow at or near the top of a volcano, through which volcanic gas, lava, and
or/pyroclastic material are ejected. The term derives from the Greek word for “wine-mixing bowl.”
Crystal: In mineralogy, the regular polyhedral (many faces) form bounded by plane surfaces (faces), that is the
outward expression of an orderly internal arrangement of atoms.
Crystalline Rock: A hard rock composed of interlocking crystals, typically of igneous origin.
Crystallization: Process through which crystal phases separate from a fluid, viscous or dispersed state.
Dacite: A (usually) light-colored lava with a high silica content, about 64% or more. Gas-rich dacite magmas
are commonly highly explosive, while gas-poor dacites typically form thick, viscous tongues of lava. When
particularly stiff and pasty, dacite lavas may form steep-sided domes. Dacite is a variety of andesite having
more quartz and less feldspar than andesite.
Diabase: An intrusive, plutonic igneous rock, considered to be a variety of diorite, consisting of plagioclase
feldspar and dark minerals (pyroxene). The crystals of feldspar are included within the pyroxene.
Dike: A Sheet-like body of igneous rock that cuts through, in a generally vertical direction, older rock
formations. Dikes form when relatively narrow, thin magma sheets intrude a volcanic cone or other structure
intersecting previously existing strata.
Diorite: A granular, intrusive, plutonic igneous rock consisting mostly of plagioclase feldspar and some
hornblende, while lacking quartz. Diorite is midway between a granite and a gabbro in chemical and
mineralogical composition and dark minerals are more in evidence than in granite. Gray is the most common
color. Diorite has the same chemical composition as andesite.
Dip: The angle and direction at which a stratum or any tabular plane is inclined from the horizontal.
Dome: A generally rounded protrusion of lava that, when erupted, was too viscous to flow far laterally and
instead piled up over the erupting vent to form a mushroom-shaped cap. When the lava mass is a
consolidated lava conduit filling, the resultant extrusion is called a plug dome.
Epoch: A division of a geologic or evolutionary time period such as the Pleistocene Epoch of the Quaternary
Period.
Erratic: Markedly different type of rock lying in terrain not its source. Erratics are rocks/boulders that were
removed from bedrock by a glacier, carried some distance away by the glacier and deposited, when the ice
melts, upon a rock surface that is unlike the rock of the erratic’s origin.
Eruption: The geologic process by which solid, liquid, and gaseous materials are ejected onto the Earth’s
surface by volcanic activity. Eruptions vary in behavior from the quiet overflow of molten rock (effusive
type) to the tremendously violent expulsion of pyroclastic material.
Exotic Terrane: A small plate fragment or microplate attached to a larger plate, but of distant origin. May have
been transported by continental drift or transform faulting.
Extrusive Igneous Rock: Igneous rock derived from magmatic material ejected at the earth’s surface by
volcanic activity. Contrasts with intrusive or plutonic rocks that cool or solidify at depth in the earth’s crust.
Fan: A deposit, usually alluvial, of rock and sediment debris at the foot of a steep slope with an apex at the
mountain base
(canyon mouth) and a radial, fan-like divergence downslope therefrom.
Fault: A crack or fracture in the Earth’s crust along which there has been differential movement (displacement).
It may represent the juncture between two adjoining crustal blocks or plates into which the Earth’s surface is
broken. Movement along a fault can cause earthquakes, or, in the process of mountain building, can release
underlying magma and permit it to rise to the surface, creating a volcanic eruption.
Feldspar: The word feldspar is from German meaning “field crystal.” The feldspars are the most common
family of minerals and are characterized by having two cleavages at nearly right angles. The crystal structure
permits considerable ionic substitution, giving rise to two major types of feldspars: 1) the orthoclase group
of aluminosilicates combined with potassium creating potassium feldspar (K-feldspar) which is commonly
pink in granitic rocks. and 2) the plagioclase feldspar group of aluminosilicates which permit complete
substitution of the alkalis sodium for calcium in the crystal structure. Feldspars are common in most igneous
rocks, in many metamorphic rocks and in some sandstones. One of the most important constituents of
igneous rocks, feldspar is nearly as hard as quartz but does not appear as glassy. Orthoclase feldspar may be
pink while plagioclase feldspar is white to dark gray. Many fragments of feldspar display a multitude of
closely spaced parallel lines and the mineral will not fizz in acid.
Firn Line: An average line or elevation on a mountain above which ice lies on the ground throughout the year.
Fumarole: A vent or opening through which issue steam or other volcanic gasses, such as hydrogen sulphide.
Gabbro: A coarse grained, intrusive, plutonic, igneous rock composed almost entirely of feldspar (plagioclase
variety) and dark minerals (dark minerals are more than 50% of content), in almost equal amounts; richer in
iron, magnesium and calcium and poorer in silica than granite. Quartz is absent from gabbro.
Geothermal Gradient: Rate of temperature increase associated with increasing depth beneath the Earth’s
surface, normally about 25 degrees C per kilometer.
Glacier: A large, dense mass of ice, formed on land by the compaction and recrystallization of snow, which
moves downslope because of its weight and gravity. Active glaciers are effective eroding and depositional
agents and have played an important role in sculpturing and otherwise contributing to the present shape of
much of the surface of the Sierra Nevada Mountains.
Gneiss: A metamorphic, coarse-grained, banded rock in which layers of granular minerals alternate with layers of
flaky ones.
Granite: A coarse grained, intrusive, plutonic, igneous rock composed of quartz and feldspar; granite usually
has a salt and pepper appearance that reflects the grainy texture and mixed coloring of the rock’s minerals.
Glassy grains are quartz while the shiny, pink, white or gray grains are mica or feldspar. The few black or
brown grains are mica, amphibole or pyroxene. In chemical composition, granite is equivalent to rhyolite,
relatively rich in silica, potassium and sodium. In modern usage, granite refers to a collection of rocks that
are similar in their origin and coloring but display differences in the exact proportion of their chemical
constituents. Granodiorite and quartz monzonite are examples of granitic rocks.
Granodiorite: A member of the granite family, granodiroite is a coarse grained, intrusive, plutonic, igneous rock
intermediate between quartz monzonite and quartz diorite. Granodiorite contains more plagioclase feldspar
than true granite and less than quartz diorite.
Hanging Valley: A U-shaped tributary and truncated glacial valley the floor of which is much higher at its
mouth than the floor of the lower, wider U-shaped trunk valley. If the floor of the hanging valley is occupied
by a stream, the flow forms a waterfall as it plunges over the lip of the truncated valley mouth to the floor of
the trunk valley below.
Holocene Epoch: The 10,000 to 12,000 year-long span of time that has elapsed since the end of the Pleistocene
Epoch (IceAge). It is the division of geologic time in which we now live.
Horn (Matterhorn): Pyramidal steep-sided alpine peak; an erosional remnant created where glacial ice has
eroded away surrounding rock material from at least three sides (cirques are often positioned just below the
horn).
Hornblende: A (usually) dark-colored mineral, the commonest member of the amphibole minerals, commonly
found in igneous and metamorphic rocks.
Hot Spot: A persistent heat source in the upper mantle unrelated to plate boundaries. Isolated “hot spots”
generating magma are believed to underlie the Hawaiian Islands and the Yellowstone region.
Igneous Rock: From the Latin world for “fire,” igneous refers to rocks derived from the solidification of magma.
Igneous rocks that congeal beneath Earth’s surface are called plutonic or intrusive, while those formed on the
surface are volcanic or extrusive.
Intrusive Rock: An igneous rock body that, while fluid magma, penetrate into or between other rocks, but
solidify before
reaching the surface.
Island Arc: A curving line of volcanic islands formed along the boundaries of converging tectonic plates.
Juan de Fuca Plate: A relatively small segment of the Pacific Ocean plate that is presently being subducted
beneath the margin of the North American plate. The Juan de Fuca slab extends from northern California
northward to southwest British Columbia.
Lapilli: The Latin terms for “little stones,” it is applied to round to angular, “pea-sized,” rock fragments
measuring 0.1 to 2.5 inches in diameter, which are erupted explosively in either a solid or molten state.
Lateral Moraine: A ridge-like accumulation of bouldery, unsorted, debris (till) pushed to the side of an
advancing glacier or deposited along the lateral margin of a retreating glacier.
Lava: Magma that reaches the Earth’s surface through a volcanic eruption. The term is most commonly applied
to streams of molten rock flowing from a volcanic vent. It also refers to solidified volcanic rock.
Lithosphere: The rigid outer shell of the Earth, including the rock crust and upper mantle.
Mafic: Pertaining to rocks composed dominantly of iron and magnesium silicates. Contrasts with sialic.
Magma: Gas-rich molten rock confined beneath the Earth’s surface; when erupted at the surface it is called lava.
Magma Chamber: Underground pocket or reservoir of magma, from which the molten material erupted by
volcanoes is drawn.
Magmatic Fluids: Volcanic gases, particularly water and carbon dioxide, dissolved in magma.
Magnetic Pole: A region where the strength of the Earth’s magnetic field is greatest and where the magnetic
lines of force apparently enter or leave the Earth. A magnetic field is the region in which magnetic forces
exist.
Magnetic Reversal: A change in the polarity of the Earth’s magnetic field. The last magnetic reversal occurred
about 700,000 years ago.
Mantle: That portion of the Earth’s interior lying between the molten core and the rigid outer crust, a zone of
hot plastic rock extending approximately 1800 miles beneath the surface. This is the region in which magma
is generated.
Meta-: Prefix indicating that rock has been metamorphosed.
Metavolcanic: Rocks formed by metamorphism of volcanic materials.
Melange: A heterogeneous mixture of rock materials, often pervasively sheared, of angular and variable-sized
blocks, often from local or distant sources, developed in a subduction zone.
Mica: The mineral group, micas, are potassium aluminum silicates containing water in the form of hydroxyl ions.
Two varieties are common, muscovite, a white or clear mica belonging to the sialic group of minerals and
biotite, a dark mica rich in iron and magnesium and therefore belonging to the category of mafic minerals.
An unusual mica in the Sierra Nevada is mariposite, a green mica containing chrome. All mica splits or
separates into thin, flaky, tough, often transparent and usually elastic sheets or laminae. Mica will not fizz in
acid and glimmers in the sun. Tiny fragments in stream bottoms can be easily mistaken for gold (which is
much heavier). Mica is abundant in granites and in many metamorphic rocks and is also a significant
constituent of many sandstones.
Mohorovicic: Discontinuity: the boundary separating the Earth’s crust from the mantle beneath it, sometimes
called the “Moho.”
Monzonite: A member of the granite family, monzonite is a plutonic igneous rock containing plagioclase
feldspar and orthoclase feldspar and dark minerals, but very little or no quartz. It is commonly darker gray
than granite but not as dark as diorite.
Moraine: A typically linear ridge of rock fragments (usually called till) deposited by a glacier. Moraines can be
classified as terminal, recessional, lateral, or ground. A landform resulting from glacial deposition. The word
“moraine” is French for “rubbish heap.”
Nuee Ardente: A “glowing cloud” of hot volcanic ash and gas that typically rises above and extends beyond the
margins of
a pyroclastic flow.
Obsidian: A dense, black, glassy volcanic rock almost devoid of bubbles and mineral crystals because it cooled
so rapidly that it didn’t crystallize. It is formed from highly silicic magma, ranging from dacite to rhyolite.
Young domes and flows of obsidian occur at the Mono Craters in the Mono Basin.
Oceanic Crust: The relatively thin slabs of basaltic crust forming the ocean floors.
Oceanic Ridge: A large submarine mountain range formed by volcanic eruptions along fissures on the ocean
floor.
Olivine: Important rock-forming iron and magnesium silicate mineral, especially in mafic or ultramafic rocks.
Olivine is olive-green, hard, commonly found in basalt and probably is a major constituent of the mantle..
Ophiolite: A group of basic and ultrabasic igneous rocks, ranging from basalt to gabbro and peridotite, including
rocks rich in serpentine. Regarded as a sample of oceanic crust and often associated with a subduction zone.
Orthoclase: A common white or pink mineral of the feldspar group having two good cleavages at right angles,
and found in high-silicon content rocks, especially granite.
Paroxysm: A violently explosive eruption of great magnitude.
Pegmatite: An intrusive, plutonic, igneous granitic rock with very large crystals, usually quartz, feldspar, and
mica. Although it can be of any composition it usually has the same mineral composition as granite. Very
coarse grained and usually occurring in dikes or veins associated with a mass of finer-grained plutonic rock.
Pelean Eruption: A violently explosive eruption that produces pyroclastic flows and is often associated with
dome-building activity. This type of eruption is named for the 1902 activity of Mount Pelee, a volcano on
the Caribbean island of Martinique. Pelean eruptions have occurred at the Mono Craters location.
Pendant (roof): A large mass of metamorphic rock within a younger intrusive rock, thought to have hung down
into the original intrusive body from the roof of the intrusive chamber. Roof pendants are present is various
locations atop the Sierra Nevada batholith and represents remnants of the rock into which the batholith
intruded but have not yet been eroded away.
Peridotite: Intrusive, plutonic, igneous rock in which grains are coarse and large enough to distinguish from one
another. Peridotite is composed of dark minerals, particularly olivine, with no quartz. Rock is darkly
colored, usually dark green or black Most peridotite in the Sierra Nevada has been altered to serpentine.
Phreatic Eruption: A violent steam explosion that produces little or no new lava. It typically ejects solid
fragments of pre-existing rock from the volcanic structure. Triggered by the conversion of ground water into
steam by an underground heat source, small phreatic eruptions characterize the opening stage of many
eruptive episodes. Red Cinder Mountain (Red Hill) in Rose Valley is a phreatic cone and the Inyo Craters
are the consequence of phreatic eruptions.
Pillow Lavas: Lava structure consisting of an agglomeration of rounded masses that resemble pillows; occurs in
basic volcanic rocks erupted under water.
Plagioclase: A group of closely related soda-lime feldspars varying in composition from acidic to basic. It is
found in most igneous rocks, is common in metamorphic rocks, and shows twinning striation on good
cleavage surfaces. “Plagio” is from the Greek meaning “oblique” or “side or sideways.”
Plastic: Capable of being molded or bent under stress.
Plate (Tectonic): A large rocky slab of the Earth’s crust that slowly moves over the plastic upper mantle beneath
it. The Earth’s crust is comprised of approximately 12-21 distinguishable tectonic plates.
Plate Tectonics: An important geologic theory stating that the Earth’s rigid outer shell is broken up into about
12 -21 distinguishable slabs or plates that are in constant motion. Concentrations of earthquakes and
volcanic activity occur at the boundaries between plates.
Pleistocene Epoch: The division of geologic time immediately preceding the Holocene Epoch having begun
about 1.6 - 2.0+ million years ago and lasting until about 10,000 or 12,000 years ago. The Pleistocene
period was characterized by repeated development of large continental ice sheets and mountain glaciers in
most of the world’s major mountain ranges including the Sierra Nevada Mountains. Many of the volcanic
features encountered in the Owens Valley and Mono Basin were formed during the Pleistocene Epoch.
Plinian Eruption: The kind of violently explosive eruption named after Pliny the Younger who wrote of the
catastrophic eruption of Mt. Vesuvius, Italy, in A.D. 79. The term is commonly used to denote the phase of
an eruption in which violently up-rushing gas carries large volumes of fragmental rock high into the
stratosphere. It also refers to a paroxysmal outburst like that of Vesuvius, producing large volumes of
tephra, pyroclastic flows, and the formation of a caldera caused by the collapse of the volcano’s former
summit.
Pliocene Epoch: A division of geologic time immediately preceding the Pleistocene and lasting from about
12,000,000 to about 2,000,000 years before the present.
Plug: Solidified lava that fills the conduit of a volcano. It is commonly more resistant to erosion than the
material composing the surrounding cone and may remain standing as a solitary pinnacle or “neck” when the
rest of the original edifice has been eroded away.
Pluton: A body of igneous rock intruded into the crust that solidifies at depth. Named for the god of the
underworld, Pluto, plutons range in size from less than one mile in diameter to more than 500 square miles;
all of them extend downward an unknown distance into the earth. Some plutons may be adjacent, although
they are distinguishable from one another while others are separated form one another by areas of
metamorphic rock or by bands of other types of igneous rocks in the form of dikes. A collection of adjacent
plutons that extend over a sizable area may be termed a batholith.
Porphyry: Any intrusive igneous lumpy rock containing coarse crystals in a finer-grained mass (matrix). Some
crystals are much larger than other.
Pumice: A highly porous volcanic rock fragment formed of glassy lava-foam blown from a vent. Usually lightcolored, pumice is typically so full of tiny bubbles or vesicles that it is buoyant.
Pyroclastic (Pyroclast): Volcanic rock that is erupted in fragments, from the Greek word for “fire-broken.”
Pyroclastic Flow: An avalanche of incandescent rock fragments and hot gas that travels downslope like a heavy
fluid. A pyroclastic flow may be composed of either pumice or dense lithic (non-vesicular) rock debris, or be
a combination of both.
Pyroxene: An important group of rock-forming iron and magnesium silicate minerals. Pyroxene resembles
amphibole except that pyroxene breaks at nearly right angles and crystals are short and stubby rather than
long and thin. Unlike amphibole which breaks (cleaves) at right angles, pyroxene cleaves at oblique
angles(56o and 124o). An end view of a pyroxene crystal is early a square. Comprised chiefly of calcium and
magnesium, pyroxene is usually found in dark-colored igneous rocks; is common in gabbro.
Quartz: Quartz is the usually the last mineral to from in granite and is thus forced to grow in the spaces between
the earlier-formed feldspars and micas. As a result quartz in granite typically lacks well-developed crystal
faces. Composed of silicon and oxygen, quartz is the most common and most durable family of common
minerals. Although commonly clear, especially if it is a constituent of granitic rock, pebbles and boulders of
white (milky) quartz are common in the Sierra Nevada. Mineral quartz is likely to display a vitreous luster
(sparkle like tiny glass beads) and will neither scratch nor effervesce (fizz) with acid
Quartz Monzonite: Plutonic rock containing quartz and approximately equal amounts of plagioclase and
orthoclase feldspar. Intermediate between granodiorite and granite.
Quartzite: A rock formed by metamorphism of sandstone or chert, which is hard, coherent and consists of
quartz.
Quaternary: The youngest geologic period, encompassing the Pleistocene and Holocene epochs, which began
about 2,000,000 years ago and including the present time.
Rhyolite: Extrusive equivalent of a granite. A generally light-colored lava rock with an extremely high silica
content (72% or more) and so fined grained that minerals are too small to be distinguished even with a hand
lens. A few larger fragments of quartz, feldspar, or pumice may be visible. Rich in sodium and potassium, it
is thick and pasty when erupted. Because gases dissolved in rhyolitic magma cannot escape easily, it can be
extremely explosive.
Rift System: Linear spreading centers along plate boundaries where crustal plates are separating and moving
apart. Magma is erupted along active rifts, creating new crust.
Schist: Metamorphosed crystalline rock that splits readily into flakes or slabs. Most grains are large enough to
be seen easily.
Scoria: Glassy fragments of dark-colored volcanic rock, less porous than pumice, commonly the product of jets
of semi-liquid lava shot into the air or the vesicular crust on the surface of lava flows.. Scoria fragments
range in size from 0.1 to 2.5 inches. Scoria is darker and heavier than pumice.
Sea-Floor Spreading: Term describing the volcanic creation of new sea floor as lava erupts along mid-oceanic
ridges, pushing the older oceanic floor away from the actively erupting fissures. This process pushes oceanic
plates away from the spreading centers toward the edge of continents, where the sea floor is subducted
beneath continental margins.
Serpentine: A rock, usually oily green and sometimes spotted, consisting largely of the mineral serpentine, a
hydrous magnesium silicate, produced by alteration of ultramafic (rich in iron and magnesium) igneous rocks.
Sialic: Pertaining to rocks composed dominantly of silicon and aluminum. Contrasts with mafic.
Silica: The term used for the chemical combination of silicon and oxygen, a primary constituent of volcanic
rocks.
Silicic Lava: A term describing lava rich in silica (over 62-64%) and having a relatively low melting point (about
850 degrees Centigrade). Silicic magma typically emerges as a stiff, viscous mass and does not flow long
distances. Silicic lavas may congeal near the eruptive vent to form steep-sided domes such as at Mammoth
Mountain, Mammoth Domes, Mammoth Craters, Obsidian Dome and Wilson Butte.
Sill: A tabular intrusive body of igneous rock parallel to bedding of the enclosing sedimentary rock. Relatively
thin compared to its lateral extent.
Snow Line: The line, as on a mountain, above which, there is perpetual snow. The snow line separates the zone
of accumulation from the zone of ablation.
Striation: A short, narrow mark, often a few millimeters deep and many centimeters long, on rock surfaces,
produced by abrasion; frequently the result of glacial action.
Subduction: The process by which sea floor is pulled or dragged beneath the margin of a continent or island arc.
Subduction Zone: The region of convergence of two tectonic plates, one of which sinks beneath the other.
Tarn: An alpine lake that occupies a cirque. Sometimes refers to a mountain lake held in place by a moraine.
Tectonics: The study of the formation and deformation of Earth’s crust that results in large-scale structural
features. The word tectonic comes from the Greek tektonikos and refers to building or construction.
Tephra: The term used by Aristotle to describe all the pyroclastic material that has been thrown into the air
above a volcano. Tephra can range in size from fine dust and ash to lava fragments many tens of feet in
diameter.
Terrane: An extensive area of related rock outcropping.
Terminal Moraine: A ridge-like accumulation of rock debris pushed and/or carried by a glacier and deposited at
the end of the glacier snout, marking its farthest advance.
Till: Unstratified (unlayered) rock debris carried and deposited by a glacier, typically consisting of unsorted
gravel, boulders, clay and sand.
Travertine: An accumulation of calcium carbonate formed by precipitation and deposition from ground or
surface waters, commonly porous and cellular.
Tufa: Calcareous rock formed around a hot spring where the calcium precipitates to combine with other
minerals, commonly carbonate. Tufa towers of Mono Lake were formed as calcium-carbonate accretions at
the orifices of freshwater springs that opened on the floor of Mono Lake. Tufaceous refers to tufa.
Tuff: Volcanic rock composed of a fine-grained pyroclastic material, such as the deposit of an ash flow. A
microscope shows tuff to consist of very tiny pieces of volcanic glass or rock or both. Tuff may be mixed
with clay, sand or pebbles. Welded tuff is a rock formed from fragmental material hot enough to fuse or weld
together when emplaced.
Ultramafic: Applies to rocks containing less than 44 percent silica but rich in magnesium and iron minerals.
Unconsolidated: Term referring to rock particles that are loose, separate, or unattached to each other. Tephra
eruptions typically from unconsolidated deposits that are easily eroded.
U-Shaped Valley (Trough): A term referring to the typical U-shaped cross-section of a glacial valley whose
walls have
been steepened and bottom flattened by glacial erosion. U-Shaped valleys, such as the valley
of
Convict and June Lakes and the valleys of Rush, Parker, Walker and Lee Vining creeks, and the Middle Fork
of the San Joaquin river are common features of the Sierra Nevada Mountains.
Vent: an opening, typically cylindrical in form, in the Earth’s surface through which volcanic material is ejected.
Vesicles: Pores of tiny cavities in a volcanic rock formed by the development of gas bubbles in the liquid magma.
Some pumice is vesicular enough to resemble a sponge.
Viscosity: A measure of a liquid’s resistance to flow. In magma, viscosity is largely determined by temperature,
gas content and the chemical composition of the molten material, particularly its silica content.
Vitric: A term describing volcanic material consisting mainly of glassy matter, such as vitric ash, which is at least
75% glass.
Welded Tuff: A fine-grained volcanic rock composed of pyroclastic material that was so hot when emplaced
that its fragments fused together. The Bishop tuff of the volcanic tableland south of the Long Valley Caldera
is a welded tuff.
Zone of Ablation: The portion of a mountain glacier below the zone of accumulation where air temperatures at
the surface of the glacier are higher than further up slope and glacier ice melts and/or evaporates.
Zone of Accumulation: Site of origin for a mountain glacier. Usually the site of a basin/depression-like feature
at high elevation (often on a north-facing slope) where accumulated snow and ice, under pressure of its own
weight, flows outward and subsequently down-slope as a glacier.
DITTIES FOR REMEMBERING ORDER OF GEOLOGIC AGES
PALEOZOIC ERA memory ditty [Campbell’s Ordinary Soup Develops Mysterious Pains in the Pants]
[CAMBRIAN, ORDOVICIAN, SILURIAN, DEVONIAN, MISSISSIPPIAN, PENNSYLVANIAN,
PERMIAN]
MESOZOIC memory ditty [TRIASSIC, JURASSIC, CRETACEOUS]
CENOZOIC memory ditty [Pink Elephants On My Pink Pajamas]
[PALEOCENE, EOCENE, OLIGOCENE, MIOCENE, PLIOCENE, PLEISTOCENE]