Download Geologic Setting - cuyamacageography

Directions:
Take I-5 South. Exit at Coronado Ave. Turn right onto Coronado Ave. and head west
for approx. three miles (it becomes Imperial Beach Blvd.). Turn left onto Third Ave. at
the four-way stop (you'll see the Reserve's concrete sign). Follow the road around the
corner and the Visitor Center will be on the right.
Stop #1 North end of Sweetwater Lake.
“Sweetwater Dam started as a 60-foot high structure. However, it was designed
so that it could be expanded in height. During construction, additional analysis of
the reservoir area showed that raising the dam to 90 feet would store five times
more water in the reservoir. So, as the 60-foot high structure was nearing
completion in January 1887, the decision was made to continue work for another
16 months to raise the dam to 90 feet. It was finally completed in April 1888, and
it provided a valuable water supply for the area. Then in 1895, a rain of six inches
in a 24-hour period created a flood greater than the designers had anticipated.
There was no precedent for expecting that much rain and runoff in a short period.
The result was that Sweetwater Dam was overtopped for a period of 40 hours,
with the highest reservoir level 22 inches over the elevation of the parapet.
Sweetwater Dam remained stable during this event. The cascading water caused
erosion downstream of the structure and washed away some of the pipeline and
other facilities, but did not adversely affect the dam. Following this flood, the
parapet was repaired and raised two feet, but with 200 feet in the middle left as an
overflow weir or spillway. An additional spillway was added on one side of the
dam, to convey flood flow through the dam, rather than have it pass over the dam.
An apron was added below the spillway to convey floodwater safely past the
structure. The walls of the canyon below the dam were protected with concrete
and steel beams. A 15-foot high wall was also constructed 50 feet downstream
from the dam as a water cushion basin for flow going through the 200 foot
overflow spillway. This basin would absorb the impact of water falling from a
height of about 90 feet over the dam.” The Journal of San Diego History Winter
2002, Volume 48, Number 1
The Sweetwater Dam was built to accommodate the growing population in Chula Vista
and National City. On opening day, water was poured out a giant hose with signs that
said “Water to Waste”, and water systems were installed to usher in a period of
successful citrus crop, and for a time Chula Vista was the Lemon Capital of the World.
Development has continued to this day, fueled in part by this water source. Following
this development, invasive plants and species such as Arrundo and Pampas Grass have
edged out native species.
The La Nacion Fault runs near this area from the south near the US/Mexico border north,
and it approximated to end near the intersection of I-15 and I-805.
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Question #1: The dam changed the geography of the area. What other kinds of changes
happen when a dam is built?
Question #2: What non-native plants do you see at this location?
Stop #2 the Tijuana Estuary
Tijuana Estuary is a small intertidal coastal estuary on the international border between
California and Mexico. The estuary is primarily a shallow water habitat, though it is often
termed an "intermittent estuary," as it is subjected to extreme changes in stream flow at
different times of the year. Extended periods of drought leave parts of the estuary dry
during some periods, while flooding inundates the same areas during others. For this
reason, Tijuana Estuary is considered to be a very unique part of the National Estuarine
Research Reserve System.
The Tijuana River Estuary is one of the few salt marshes remaining in Southern
California, where over 90% of wetland habitat has been lost to development. The site is
an essential breeding, feeding and nesting ground and key stopover point on the Pacific
Flyway for over 370 species of migratory and native birds, including six endangered
species.
A marker on the bluff, first placed there in 1851 just after the treaty of Guadalupe
Hidalgo, delineates the western beginning of the International Border.
Border Field State Park is located in the southwestern corner of the Reserve, on a bluff
overlooking the ocean, the estuary, and the bull ring that lies just south of the
U.S./Mexico border.
For more information about the Tijuana Estuary and Border Field State Park please visit
www.tijuanaestuary.com and The California Coastal Records Project at
http://www.californiacoastline.org/cgi-bin/image.cgi?image=10086&mode=
sequential&flags=0&year=2002
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Stop #2 the Tijuana Estuary
Tijuana Estuary is a small intertidal coastal estuary on the international border between
California and Mexico. The estuary is primarily a shallow water habitat, though it is often
termed an "intermittent estuary," as it is subjected to extreme changes in stream flow at
different times of the year. Extended periods of drought leave parts of the estuary dry
during some periods, while flooding inundates the same areas during others. For this
reason, Tijuana Estuary is considered to be a very unique part of the National Estuarine
Research Reserve System.
The Tijuana River Estuary is one of the few salt marshes remaining in Southern
California, where over 90% of wetland habitat has been lost to development. The site is
an essential breeding, feeding and nesting ground and key stopover point on the Pacific
Flyway for over 370 species of migratory and native birds, including six endangered
species.
A marker on the bluff, first placed there in 1851 just after the treaty of Guadalupe
Hidalgo, delineates the western beginning of the International Border.
Border Field State Park is located in the southwestern corner of the Reserve, on a bluff
overlooking the ocean, the estuary, and the bull ring that lies just south of the
U.S./Mexico border.
For more information about the Tijuana Estuary and Border Field State Park please visit
www.tijuanaestuary.com and The California Coastal Records Project at
http://www.californiacoastline.org/cgi-bin/image.cgi?image=10086&mode=
sequential&flags=0&year=2002
All things in an environment can be classified as either biotic or abiotic.
Estuary
The Tijuana
Question #1: Please describe the physical site conditions that characterize each of
the marshland habitat, and explain how the plant communities have adapted to the
physical sites on which they occur (including examples of drought survival strategies
as appropriate.)
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Question #2: Making a Food Pyramid, place the Biotics in context of Primary
Producers (plants), Primary Consumers, Secondary Consumers, Tertiary
Consumers and Detritovores. (You will see this inside the Visitor’s Center)
Primary
Secondary:
Tertiary
Question #3: What is one of the strategies of the plants in this ecosystem that allows
them to survive in salt water?
Question #4: What types of birds and other wildlife do you observe at this site?
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Question #5: What are some of the properties of the marsh that make it worth
preserving alongside this urban environment?
Questions #6: How does the Tijuana Estuary’s location so near the U.S./Mexico
border help or hinder the efforts for protection?
Question #7: If you have a GPS at a location, mark a location that is easily found on
a Google Earth aerial or satellite photograph. Please mark a UTM and
Longitude/Latitude point. Then, when you get home, check to see if your GPS
reading is the same as the reading for Google Earth.
UTM Coordinate:______________________________________
Longitude/Latitude Coordinates: __________________________N
_________________________W
Name of site you have marked _____________________________________
Question #8: List some of the various wildlife you have found during this walk:
Birds:
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Plants:
Insects:
Aquatic Creatures:
Directions:
Exit the Tijuana Estuary via 3rd Street, and turn right onto Palm Ave. Go to Rainbow
Street, and follow this to SR-75/Silver Strand Blvd.. Turn left onto SR-75/ Silver Strand
Blvd. Drive approximately 1.1 miles, turning right into the parking area at the Biological
Observation State at the San Diego Bay National Wildlife Complex, South Bay Salt
Flats.
Stop #3 Biological Observation Station at the San Diego Bay National
Wildlife Refuge Complex, South Bay Salt Flats
The San Diego Bay is entirely surrounded by the development of 5 cities, including
Chula Vista, Coronado, Imperial Beach, National City and San Diego; open spaces
include portions of the Sweetwater and Otay River corridors. It also includes two major
Naval Facilities: North Island or the Naval Base Coronado, and The Silver Strand
Training Complex, formerly known as the Naval Radio Receiving Facility (NRRF), has
become the primary training facility for the military's Special Forces.
Across the street from the salt flats, facing the ocean is a facility often called "elephant
cage" which is the nickname of the large landmark, the "Wollan Weber" circular antenna.
The antenna was used to provide primary communication links for the Navy's submarine
community. Today this 450-acre facility is used for training Navy Seals for approaches
from both the Pacific Ocean and San Diego Bay sides, as well as a site for urban warfare
training.
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Naval Base Coronado is called North Island because prior to World War II, it was
technically an island. There was a small watercourse that spanned an area between
Coronado and North Island. However, during World War II, the base was expanded, and
the area filled in. The Naval Base Coronado houses aircraft, warships and is responsible
for environmental cleanup should any oil spills or other types of environmental accidents
occur in the bay.
The 3,940 acre San Diego Bay National Wildlife Refuge Complex, South Bay Unit, was
dedicated in June of 1999. This land includes portions of open bay, active solar salt
evaporation ponds, and the western end of the Otay River drainage basin.
Because development had eliminated 90 to 100 % of submerged lands, intertidal
mudflats, and salt marshes north and central San Diego Bay, the new South Bay refuge
preserved and continues to restore the remaining wetlands, mudflats and eel grass beds to
ensure that the bay's thousands of migrating and resident shorebirds and waterfowl will
continue to have habitat into the future.
The San Diego Bay supports numerous endangered and threatened species of plants and
animals and is a vital link to other wildlife areas. Rare eel grass beds, thousands of
resident and over-wintering waterfowl, seabirds, shorebirds and the largest contiguous
mud-flat in southern California make this refuge an essential resource for numerous bird
species, and an important stop on the Pacific Flyway (see map attached.) For this very
reason, San Diego Bay is a favorite of bird watchers throughout the county, and is one of
the locations observed for both the San Diego Bird Atlas and the Annual Audubon
Society Christmas Bird Count.
The Rose Canyon Fault begins at this end of the San Diego Bay. It extends through Rose
Canyon (to see this, go to Morena Blvd. to the Costco) and north to Torrey Pines.
Question #9: What is the prominent feature located on the Rose Canyon Fault?
Question #10: How is this site different from the Tijuana Estuary?
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Question #11: From this vantage point, you can see the mesas in relation to the City
of San Diego. Please describe an inversion that would form because of these mesas
visible from this site.
Question #12: What are some of the environmental impacts of development on this
marsh environment?
Question #13: What types of wildlife do you see at this location?
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Directions:
Depart the parking area, and turn right onto Silver Strand Blvd. Drive 3.5 miles, bearing
left onto Orange Ave., then follow the signs to cross over the Coronado Bay Bridge
returning to Interstate 5. Take the on-ramp for Interstate 5 North, and travel for 17.5
miles and exit at Clairemont/Mission Bay Dr. (exit 22). Turn right onto East Mission
Bay Dr. and drive 0.9 miles to the parking lot for De Anza Cove. This is a great place to
stop for lunch.
Stop #4 Mission Bay
Geologic Setting
San Diego County can be divided between three distinct geomorphic regions: the Coastal
Plain region as exposed west of the Peninsular Ranges, the Peninsular Range region, and
the Salton Trough region as exposed east of the Peninsular Ranges. This geomorphic
division reflects a basic geologic difference between the three regions, with Mesozoic
metavolcanic, metasedimentary, and plutonic rocks predominating in the Peninsular
Ranges, and primarily Cenozoic sedimentary rocks predominating to the west and east of
the central mountain range. The irregular contact between these geologic regions reflects
the ancient topography of this area before it was buried by the thick sequence of
Cretaceous and Tertiary sedimentary rocks deposited over the last 75 million years by
ancient rivers and in ancient seas.
Together, these rocks and their contained biological record (i.e., fossils) document the
geological and biological evolution of this part of western North America. They record a
time when consumption of an ancient oceanic crustal plate created an archipelago of
volcanic islands, and when this same plate subduction produced massive volumes of
magma that later congealed in the crust to form plutonic rock.
Local rocks also record an early period when tectonic forces uplifted and erosion exposed
the plutonic rocks to form a mountainous coastline, similar to the Andes along the west
coast of South America.
Also recorded are periods of higher rainfall and subtropical climates, which supported
coastal rain forests with exotic faunas and floras; periods of drowned coastlines, great
rivers, and relentless erosion; periods of extreme aridity and renewed volcanism; and
periods of widespread faulting and crustal shear and the formation of new seaways.
Question #14: What are the visible differences between the South Bay Salt Marsh
and De Anza Cove?
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Question #15: If you have a GPS at this location, mark a point that is easily found
on a Google Earth aerial or satellite photograph. Please mark a UTM and
Longitude/Latitude point. Then, when you get home, check to see if your GPS
reading is the same as the reading for Google Earth.
UTM Coordinate:______________________________________
Longitude/Latitude Coordinates: __________________________N
_________________________W
Name of site you have marked _____________________________________
Coastal Plain Region
The Coastal Plain Region is underlain by a "layer cake" sequence of marine and nonmarine sedimentary rock units that record portions of the last 140 million years of earth
history. Over this period of time the relationship of land and sea has fluctuated drastically
so that today we have ancient marine rocks preserved up to elevations around 900 feet
above sea level and ancient river deposits as high as 1,200 feet.
Faulting related to the local La Nacion and Rose Canyon fault zones has broken up this
"layer cake" sedimentary sequence into a number of distinct fault blocks in the
southwestern part of the county. North of La Jolla the effects of faulting are not as
pronounced. The Rose Canyon Fault is believed to be capable of a magnitude 6 or 7
earthquake. This has been a consideration in the building methods surrounding both
Mission Bay and San Diego Bay.
Mission Bay
The gradually sloping mudflats on Fiesta Island provide habitat for shorebirds such as the
ruddy turnstone, willet, and black-billed plover. The sandy beach of the western shore is
a nesting area for the snowy plover. Many birds including the house finch, horned lark,
western meadowlark and the mourning dove nest on Fiesta Island in protected areas of
coastal chaparral. Fiesta Island has a large California least tern protected nesting site at
the northern tip of the island. The tiny elegant and lively least tern is a familiar summer
resident.
Tecolote Creek flows into the inlet of Fiesta Island creating a small marsh area where the
river meets the Bay. Many species of duck are visible during their seasonal migration.
Some of our annual visitors include the coot, ruddy duck, bufflehead, cinnamon teal,
northern pintail, green-winged teal, scaup and redhead. Loons inhabit this area year
round.
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Perez Cove is one of the three known nesting sites of the great blue heron in San Diego
County. These enormous long-legged, long-necked birds are commonly sighted nesting
in the tops of Torrey Pine trees. Throughout the year the great blue heron are visible
around bays, lagoons, ponds, and lakes throughout San Diego County. The great blue
heron feeds primarily on fish, but their diet may also include mice, small birds, frogs, and
other small animals.
Mariner's Point is home to the smallest tern species, the least tern. The California least
tern is an endangered subspecies nesting in patches of fairly flat sandy ground with little
or no vegetation. Like many species, the least tern may abandon its nest if disturbed.
Effective conservation measures, including fences and signs provide some protection for
these birds. The least tern breeds along the Pacific Coast as far north as San Francisco.
June or July is the best time to see the least tern nesting at Mariner's Point. You can see
them hovering high above the water's surface, then plunging in head first in pursuit of
small fish, or skimming low over the water.
Question #16: Please describe the physical site conditions for this area, and explain
why these marshlands are so rare and considered by scientists to have a high
conservation value.
Question #17: What are the ecological and economic impacts of San Diego’s
population pressures on this area? What are the impacts of the recreational uses of
Mission Bay?
Question #18: How will the development of Fiesta Island change this habitat?
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Directions:
Return to Interstate 5, and drive north for approximately 6 miles, and exit on Genesee
Ave. Turn left onto Genesee Ave, and drive for 1.3 miles. The name will change to
Torrey Pines Road. Drive another 1.1 miles. Turn left into the Torrey Pines State
Reserve, or go past the Reserve and turn around about a mile ahead and return to park
free in the beach parking strip.
Stop #5 Torrey Pines State Reserve
San Diego’s coastal region has a longer growing season because of maritime influences
and the Mediterranean climate. Santa Ana winds blow from the East, especially in
autumn. The rainfall is only about 10 inches per year; however coastal fog adds moisture
to this environment, both by condensation on the plants and soil and by increasing the
humidity in the air thereby lowering the transevaporation rate.
The plant communities include the coastal strand, coastal sage scrub, chaparral, Torrey
pine woodland, and salt marsh. The riparian and freshwater marsh communities are not
included, even though they slice through the coastal strip at various locations.
The vegetation associated with the Torrey pine woodland is a mixture of plants from the
coastal sage scrub and chaparral plant communities. The shrubs we will see in this area
are chamise (Adenostoma fasciculatum); manzanita (Arctostaphylos spp); Nuttal’s scrub
oak (Quercus dumosa); ceanothus (Ceanothus spp); toyon (Heteromeles arbutifolia); and
mountain mahogany (Cercocarpus minutifolus). The Nuttal’s scrub oak and Wartystemmed ceanothus (Ceanothus verrucosus) is characteristic of the Torrey Pines’
maritime chaparral plant community.
The Torrey pine (Pinus torreyana) is the most restricted and rarest pine in North
America. It grows in the Torrey pine woodland or Pacific coniferous forest. This pine is
thought to be a relict population of an ancient coastal forest which has been reduced
during the drying period of the last ten thousand years to the sandy soils of the sandstone
cliffs and canyons of Torrey Pines State Reserve and Santa Rosa Island. Extensive root
systems and deep summer fogs promote both the tree's survival and continued
proliferation. The trees along the cliff are twisted and gnarled into spectacular shapes by
the constant winds, while those which are sheltered are more robust and vertical.
The common species include Salt Grass (Distichlis spicata); Pickleweed (Salicornia
virginica); Glasswort (Salicornia subterminalis); Alkali Heath (Frankenia grandifolia);
and various species in the goosefoot family.
Most of the rocks in the Reserve were deposited in or near the ocean. Sea level has
changed relative to the land. During the last ice age, about 10,000 years ago, sea level
was 300 feet lower than now. The lagoon to our north was carved 300 feet deeper than its
present mud floor, then filled with mud when the ice melted and the sea rose. If global
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warming melts all the ice in Antarctica and Greenland, sea level will be 300 feet higher,
lapping at the Lodge.
Question #19: The forest habitat found here is called Torrey Pine Woodland.
Please describe the dominant trees that occupy this habitat and explain why there is
not a greater diversity of tree species in the area.
Question #20: The Torrey Pines are shaped by what forces in the environment?
Question #21: Please describe the habitat types found at this location.
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Faults
Faults crossing the Reserve are most easily seen in the beach cliffs The Carmel Valley
Fault hits the beach about 500 yards south of Flat Rock. The Delmar Formation dips
below the sand at about 100 yards south of Flat Rock but is raised up about 26 feet into
view again by the fault. In thin-bedded rocks another 100 yards south, even very small
faults which offset the rocks by only a few inches can be seen.
Question #22: What type of faulting is visible on the cliffs at Torrey Pines State
Reserve?
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Question #23: What type of fault is the Rose Canyon Fault?
Question #24: Which direction is Southern California moving?
Question #25: What are some of the past impacts to the local coastline from Global
Climate change and how are these visible from the cliffs?
Thank you for participating: I hope that you had a good time and learned
something of value today (and maybe even got to play in the Ocean!) Please hand in
this worksheet before leaving.
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