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The Earth Through Time, 10th Edition
by Harold L. Levin
CHAPTER 15—CENOZOIC EVENTS
CHAPTER OUTLINE FOR TEACHING
I.
Overview of Cenozoic
A. Subdivision of Cenozoic (m.y. = million years)
1. Three periods
a. Paleogene: 65.5 to 23 m.y.
b. Neogene: 23 m.y to 1.8 m.y.
c. Quaternary: 1.8 m.y. to present
2. Epochs of the Paleogene
a. Paleocene: 65.5 to 55.8 m.y.
b. Eocene: 55.8 to 33.9 m.y.
c. Oligocene: 33.9 to 23.0 m.y.
3. Epochs of the Neogene
a. Miocene: 23 to 5.3 m.y.
b. Pliocene: 5.3 to 1.8 m.y.
4. Epochs of the Quaternary
a. Pleistocene: 1.8 to 0.01 m.y.
b. Holocene: 0.01 m.y. to present
B. Plate Tectonics
1. Vast seafloor expansion
a. 50% of seafloor produced during last 65.5 m.y.
b. most new seafloor in Atlantic and Indian Oceans
2. Significant westward movement of N. and S. America
a. San Andreas fault system produced
b. Andean trench deformed
c. Cascade-Panamanian-Andean volcanic chain developed
d. extensive west coast orogensis
3. Significant rifting
a. North Atlantic: Greenland split from Scandinavia
b. South Pacific: Australia split from Antarctica
c. Indian Ocean: Arabia split from Africa (creating Gulf of Aden
and Red Sea)
4. Significant collision events
a. Africa-Eurasia: Alps built
b. India-Eurasia: Himalayas built
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5. Cenozoic characteristics
a. continents stood high: transgressions limited
b. sharply defined climatic zones
c. cooling trend culminated in Pleistocene Ice Ages
II. Pre-Pleistocene Cenozoic History
A. Eastern United States
1. Structural changes
a. broad gentle uplifts
b. eastern tilting of Atlantic Coastal Plain and shelf
c. subsiding platforms in Florida-Bahamas area
d. Neogene uplift of Florida
2. Sedimentation and erosion
a. Appalachian plains beveled by erosion
b. valley and ridge topography sculpted
c. coastal plain alluvial sedimentation
d. reworking by marine transgressions
e. coralline carbonates (2500 m) in Florida area
B. Gulf Coast
1.
2.
3.
4.
5.
6.
Best stratigraphic record in N. America
8 major cycles of transgression/regression
Paleocene transgression as far north as Illinois
Common cyclic sequence: deltaic above offshore deposits
Comprise seaward-thickening wedge of clastics
Carbonates absent in region
C. Rocky Mountains and Cordillera
1. Structural changes
a. Late Cretaceous-Paleogene accretion events account for
major structural features of western Cordillera
b. Miocene uplift and erosion exposed present topography (e.g.,
Rocky Mountains)
c. Miocene uplift resulted in re-deposition of Paleogene
sediments of intermountain basins
d. Neogene normal faults elevated the Teton Range (6000 m
displacement): Teton fault scarp is 2500 m high
2. Volcanic activity: widespread in the region
3. Sedimentation
a. Paleocene (e.g., Fort Union Fm., 1800 m thick): clastics in
intermountain basins (silt, sand, shale, coal, lignite)
b. Eocene lake deposits in intermountain basins (e.g., Green River
Fm. in basins between Wind River and Owl Creek Mountains: 600
m of freshwater limestone and shale; seasonal varves; 6.5 m.y record of insect,
plant, and fish fossils; oil shales
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c.
Eocene stream deposits (e.g., Wasatch Fm.): intermountain basin
fills, red colors; fine upward from conglomerates to siltstones
d. Eocene-Oligocene floodplain deposits (e.g., White River Fm.):
clays, silts, and ash with extensive mammal accumulations in flood deposits
e. Oligocene lacustrine deposits filled with volcanic ash (e.g.,
Florissant beds): spectacular preservation of insects, leaves, fish,
birds, spores, pollen
f. Miocene fluvial and lacustrine sedimentation (intermountain
basins) and piedmont plains (east of Rocky Mountains: grasslands
with camels, horses, rhinoceroses, deer, other grazing
animals; Great Plains developed; spectacular erosional features
g. Pliocene floodplain deposits: reflect cooler, drier conditions
D. Basin and Range Province: Nevada-Utah to Mexico
1. Structural history
a. Mesozoic over-thrusting
b. Paleogene regional arch
c. Miocene-Holocene arch subsidence and normal faulting: northsouth trending fault-block mountains (horsts and grabens)
developed by tensional forces
2. Causes of structural development: four hypotheses
a. subduction hypothesis: Pacific spreading center active below
region as it was subducted
b. oblique shearing hypothesis: tension due to west coast
shearing
3. Sedimentation
a. Miocene evaporites in lakes
b. Miocene-Holocene coarse clastic shed off of mountains
c. Miocene-Holocene clastics fill grabens
4. Volcanism: different styles on different sides of province
a. western side: extensive lava flows
b. eastern side: explosive volcanism (ash and pumice deposits)
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E. Colorado Plateau
1. Region of non-folded, flat-lying Paleozoic and Mesozoic rocks
a. crustal buttress with deformation all around it
b. plateau raised repeatedly during Early to Middle Pliocene (5 to
10 m.y. ago)
2. Structure and volcanics: steep faults are avenues for lavas (e.g., in the
San Francisco Mountains, AZ)
3. Uplift and erosion: Grand Canyon cut down 2600 m into crystalline
Precambrian rocks
F. Columbia Plateau and Cascades
1. Region built by two styles of volcanic activity
a. relatively quiet fissure eruptions covering 1/2 million km 2 with
2800 m of lava
b. explosive, violent volcanic mountain chains issuing lava,
pyroclastics, and ash clouds (nuée ardente)
2. Columbia Plateau: Neogene basaltic fissure eruptions; layered basalts
3. Cascade range
a. volcanism due to melting of down-going Juan de Fuca plate
b. volcanism began 4 m.y. ago (Pliocene)
c. recent eruptions: Mt. St. Helens, WA (1980)
d. other recent eruptions: Mt. Lassen (1914-15); Mt. Rainier (2000
years ago)
e. caldera-producing eruption: Mt. Mazama exploded to form
Crater Lake (OR) today
G. Sierra Nevada and western California
1. Sierra Nevada Mountains
a. not supported by thick crust, rather by buoyant liquid rock
b. Jurassic: formed by plutonism in Nevadan orogeny
c. Cretaceous and Cenozoic: eroded deeply
d. Pliocene-Pleistocene: range uplifted 4000 m along huge normal
faults on east side; range tilted west depressing the California
trough on west side
e. Pliocene-Pleistocene: rejuvenated streams and valley glaciers
cut present topography (e.g., Yosemite Park)
2. California west of Sierra Nevada Mountains
a. Paleocene-Miocene: affected by subduction tectonics,
deformation, volcanism
b. Miocene: conversion to strike-slip (transform) fault tectonics;
cease subduction in area
c. Miocene-Pliocene: regression due to uplift
d. Miocene-present: creation of submarine basins due to fault
movements; clastics, cherts, diatomites
e. Holocene: final regression from most western California
marine basin
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3. Alaska and arctic islands of Canada
a. Aleutian chain volcanics
b. Aleutian back-arc basin: clastics, pyroclastics, lavas
c. Alaska and Canada: clastics with coal
4. West Coast tectonics
a. East-dipping subduction: Mesozoic and Paleogene
orogenesis
b. Orogenic effects: batholiths, compressional structures,
volcanism, metamorphism, ore emplacement
c. Farallon plate: extensively melted (including spreading ridge);
northern segment = Juan de Fuca plate; southern segment =
Cocos plate
d. Pacific plate: moving northeast prior to west coast contact,
therefore strike-slip fault motion was assumed (Miocene)
e. Baja California split from Mexico: Pliocene (5 m.y. ago);
moving north on Pacific plate
H. South America: Andean orogenic belt
1.
2.
3.
4.
5.
Cretaceous: deformation, metamorphism, granitic plutonism
Cenozoic (especially Miocene): folding and volcanism
Miocene-Pliocene: highlands eroded
Late Pliocene: renewed uplift; present-day relief
Cenozoic tectonics due to continual subduction of South Pacific
plate under western S. America
6. Cenozoic clastics shed off Andes: Amazon and Orinoco basins
or intermountain rifts
I.
Tethyan Realm (Europe)
1. Eocene deformation
a. Africa moves north toward Eurasia deforming Europe and
creating Pyrenees and Atlas Mountains
b. Northern movement converts to scissor-like closure: beginning
formation of Alps
c. Flysch deposition in basins: dark marine shales, immature
sands, cherts
2. Oligocene deformation
a. enormous recumbent folds form and rise to form mountains from Tethys marine
sediments
b. compression forces folds to north on to Eurasia
c. thrust faults cut folds on undersides
d. molasse deposits: Piedmont clastic wedge shed on north side of
rising Alps
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3. Miocene deformation and sedimentation
a. glacial-induced sea-level drop of 50 m
b. tectonic restriction of inlet at straits of Gibraltar
c. factors above isolated the proto-Mediterranean from global sea;
evaporation 5.5 m.y. ago turned basin into an evaporitic basin and
eventually a desert (like Death Valley, CA today)
4. Pliocene-Holocene deformation
a. Jura folds form: older rocks transported over molasse; form
northern front of Alps today
b. Post-Pliocene uplifts continued to today
5. Similar age deformation: Apennines, Caucasus, Carpathians, and
Himalayas
J. Tethyan Realm (India)
1. Paleocene-Oligocene: folding, thrusting, granitic plutonism as ocean
closed between India and Eurasia
2. Miocene: intensive orogenic episode; elongate tracts of seafloor folded
and thrust south onto India; northern trough of India formed (5000 m
continental clastics)
3. Pliocene-Holocene: great elevation of plateaus and folded ranges;
retreat of marginal seas; continued collision of India-Eurasia; Himalaya
Mountains thus built
K. Northern Europe (France, Scotland, Ireland, Spitzbergen, Greenland, Baffin
Island)
1. Early Cenozoic lavas: Giant’s Causeway of Ireland; same age as
Greenland-Europe split
2. Paleocene-Eocene-Oligocene: repeated cyclic transgressions and
regressions into Europe
a. Oligocene: greatest transgression
b. Flooding from North Sea toward SE
c. Paris Basin: thick section above Cretaceous chalks
3. Miocene-Holocene: uplift prevented further transgressions
L. Africa
1. Northern region near Tethys: little deformation, flat-lying rocks
2. Southern region: emergent in Cenozoic
3. Eastern region: Cenozoic uplift and rifting
a. 3000 m of uplift in a broad arch
b. fracturing and normal faulting on arch crest
c. east African rift valleys formed
d. volcanic development in rifts (e.g., Mt. Kenya and Mt.
Kilimanjaro)
e. elongate lakes formed in rifts
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M. Antarctica
1. Paleocene-Eocene: Antarctica was joined with Australia and was relatively warm
2. Miocene: Separation from Australia caused warm currents to flow northward and
Antarctica became cold like today
III. Quaternary (Pleistocene and Holocene) History: the last 1.8 m.y.
A. Overview of Epochs
1. Time of ice ages
a. 40 million km3 snow and ice covered 1/3 Earth’s surface
b. glacial terrains created
c. climatic zones shifted southward
d. Arctic conditions in Europe, N. America
e. intensive rain in lower latitudes
f. human evolution and migrations
2. Climatic characteristics
a. glacial and integlacial intervals
b. ocean cooling events independent from glaciation
B. Pleistocene-Holocene Chronology (m.y. = million yrs)
1. Original concept of Pleistocene base (Lyell, 1839)
a. Marine strata young enough to contain 90-100% of presently
living mollusks as fossils
b. Lyell’s concept applied to marine strata in Italy, not worldwide
c. Non-marine record not well defined as a result
2. Modern concept: Pleistocene base = 1.8 m.y. ago
a. 1.8 m.y. widely accepted date of base
b. 1.8 m.y. does not coincide with onset of glaciation; glaciation
not a synchronous event; oldest extensive glaciation = 1.0 m.y.
c. Marine sediments: base is extinction (last occurrence) of
discoasters
d. Continental deposits: base is first occurrence of modern horse
fossils (Equus), elephants, etc.
3. Modern Concept: Holocene base
a. base defined as level (age) of melting of ice sheets to
approximately their present position and sea level rise to near
present level
b. base defined as above = 8000 yr ago
c. some geologists define base as mid-point in glacial retreat and
sea-level rise
d. base defined as above = 11,000-12,000 yr ago
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4. Independence from “ice age” concept
a. pre-1975 concept: Pleistocene consisted of 4 glacial intervals
and 3 interglacial intervals; Holocene was final interglacial
interval
b. post-1975 concept: glacial intervals are not synchronous and
more than 4 occurred, therefore epochs independent of such
constraints
c. reasoning for above: discovery of 30 intervals of severe cold
over last 3 m.y.
5. Variables affecting Earth’s climates over time
a. atmospheric changes: greenhouse versus icehouse
b. geographic and tectonic changes
c. oceanographic changes
d. astronomic changes: sunspot cycles, Milankovitch cycles, etc.
C. Terrestrial Stratigraphy of Pleistocene
1. Sedimentary deposits by environment (facies)
a. glacial (till): terminal moraine, ground moraine
b. fluvial (stratified drift): braided and meandering streams
c. lacustrine
2. Erosion surfaces
a. bedrock scour by ice
b. melt-water stream incision
c. melt-water flood (scablands)
3. Correlation and relative-age determination requires mutually sustaining
criteria
a. degree of stream dissection of moraine
b. depth of oxidation of sediment layer
c. degree of chemical weathering of layer
d. fossil pollen as climatic indicators
e. varved clays in lake deposits
f. C14 dating of wood, bone, shell, peat (note: 1/2 life = 5,570 yr)
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D. Marine Stratigraphy of Pleistocene: correlation methods in continuous core
1. Oxygen-isotope ratios in calcareous planktonic foraminifers: indicator
of water volume stored as ice in glaciers
a. O18 is heavier and is not evaporated as readily as O16, thus snow
and ice are enriched in O16
b. O18/O16 ratios from cores plotted versus depth in core show
variations in ice volume (thus, sea level) over time; also shows
climate changes
2. Relative abundance of foraminifera sensitive to temperature changes
a. Globorotalia menardii: tropical species associated with warm
waters
b. Globorotalia truncatulinoides: coils right in warm water; coils
left in cold water
c. Background sedimentation rates and ages in core determined by
C14 dating of foraminiferal tests
3. Remnant magnetism
a. depositional remnant magnetism may be correlated with known
geomagnetic time scale
b. age check by allied C14 dating
c. magnetism may be disturbed by bioturbation
E. Effects of Pleistocene Glaciation
1. Sea-level drop: 75 m below today’s level at maximum
a. continental shelves as dry lands (forests, grassland, plains)
inhabited by humans
b. land bridges: British Isles-Europe, Siberia-Alaska
c. interglacial intervals inundated shelves and bridges; forced
animal migrations
2. Glacial physical effects
a. ice-caused erosion
b. weight of ice depressed crust 200-300 m below pre-glacial level;
interglacial crustal rebound (as today); elevation of glacial
coastlines
c. obliteration of river systems by continental glaciers
d. establishment of new glacial and interglacial river drainage
basins (e.g., Missouri and Ohio Rivers)
e. changes in stream gradient and sediment load in glacial versus
interglacial times; sea level affected base levels worldwide
f. continental lakes (e.g., Great Lakes of N. America) scoured in
lowlands by continental ice sheets
g. development of huge ice-dammed lakes of a temporary nature;
huge lake bed deposits exist today (e.g., Lake Agassiz of ND,
MN, and central Canada)
h. pluvial lakes formed: thousands of large and small lakes formed
in low latitudes by excess rainfall in glacial intervals (dry during
interglacials); example: Lake Bonneville, site of salt flats and
Great Salt Lake, UT today
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i.
j.
k.
glacial impoundment lakes: impoundment floods created
channeled scablands (e.g., draining of Lake Missoula (MT)
resulted in flood of 2000 km 3 water and severe erosion
soil erosion: soil stripped off craton of Canada and
transported south
loess-blanket deposition: dense, cold air flowing off glaciers
blew fine material from tills and drift to lower latitude areas (e.g.,
loess blankets of Missouri River valley U.S.; central Europe;
northern China)
F. Causes of Pleistocene Climates
1. Any theory must account for reasons whya. climates grew cooler from Middle Cenozoic to Pleistocene
(long-term trend)
b. glacial-interglacial intervals alternate (short term trends)
c. temperature and precipitation conditions mitigate to form
proper combination
d. many factors may be involved
2. Milankovitch theory of solar radiation
a. Earth’s astronomical motion accounts for changes in amount of
solar energy received, thus spawning glacial intervals
b. Earth’s axial tilt: varies 22o to 24o over 41,000 year period
(changes seasonal length-of-day and amount of solar energy at
high latitude)
c. Earth’s axial precession: axis of rotation moves in circle with
period of 26,000 yr
d. Earth’s orbital eccentricity: varies by 2% with a period of
100,000 yr (thus Earth is closer to the sun at times)
e. Support for theory: radiometric and oxygen-isotope studies
show strong correlation to Milankovitch calculations, especially to
role of eccentricity at 100,000 yr intervals over last 600,000 yr
f. Criticism of theory: why not operative over all of geological
time?
3. Other factors affecting Milankovitch climatic change
a. albedo (reflectivity of Earth): currently 33% solar energy
reflected during this interglacial and sea level high stand; during
extreme low sea levels more continent would be exposed and
albedo higher (thus lower global temperatures); 8o C drop per 1% change
b. cloud-ash-dust absorption of solar energy
c. greenhouse gas content (especially CO2); decrease CO2 =
cooling, increase = warming temporarily but cloud cover and
excess precipitation may trigger ice buildup
d. oceanic effects: northward deflection of Gulf Stream-type
currents (e.g., 3.5 m.y. ago when Isthmus of Panama formed)
would send warmth and moisture to northern regions
e. Continental positions: continents must be at or near poles or
snow will fall in ocean and melt
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4. Milankovitch predictions of future
a. 20,000 cooling trend going into next glacial
b. unknown factors: CO2 and other atmospheric changes by humans
G. Cenozoic Climates: Global Warming, then Cooling
1. PETM – Paleocene-Eocene Thermal Maximum
a. Global warming from carbon-dioxide buildup in atmosphere
b. Gradual event spanning 10,000 years
c. Melting of sea-floor methane hydrate released methane, which formed carbon
dioxide in the atmosphere
d. Global temperatures rose 8oC during the PETM
e. Disastrous effects
(i) acid rain and acidification of the oceans
(ii) foraminiferal extinction in the oceans
(iii) major shifts of plants and animals on land
2. Oligocene cooling
3. Miocene warming
4. Pleistocene and Holocene cooling and the ice ages
Answers to Discussion Questions
1. (a) Mountains of the Basin and Range were formed during Miocene when the crust under
that region was stretched and such tension caused up-thrown blocks (horsts) to become
mountains and down-dropped blocks (grabens) to become valleys. (b) The Great Plains was
formed during Miocene when uplift of the Rocky Mountains caused great volumes of clastic
sediments to be eroded from the mountains and deposited eastward. (c) Columbia and
Snake River Plateau were formed during Cenozoic by vast outpouring of basaltic lavas
erupted along deep fissures in an area of 500,000 km 2. (d) The Red Sea was formed during
Cenozoic when a branch of the Indian Ocean rift split Arabia away from Africa and in the
process opened this seaway. (e) The Teton Range was formed when normal faulting
accompanying Neogene uplifts affected northwestern Wyoming. (f) The Cascade Range
was formed over the last 4 million years as viscous lavas were intruded into the western
margin of the American plate as a result of subduction of the Juan de Fuca plate of the
eastern Pacific.
2. The Alps, Atlas, Apennines, Carpathians, Caucasus, Pyrennes, and Himalayas are all
mountain ranges formed by the closure of the Tethys seaway.
3. Paleogene Period includes (in order from oldest) Paleocene, Eocene, and Oligocene.
Whereas, Neogene includes Miocene, Pliocene, Pleistocene, and Holocene Epochs.
4. The Green River Formation is economically significant because it contains shales rich in
waxy hydrocarbons, a deposit called oil shale that can be processed to yield petroleum. The
Green River Formation is also the source of crude oil pumped from the adjacent Wasatch
Formation. The Fort Union Formation is economically significant because it contains
immense tonnages of low-sulfur coal in its lower levels.
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5. Lake Nyasa and Lake Tanganyika are lakes formed by fault-bounded, down-dropped crustal
blocks. This normal faulting is the result of Cenozoic rifting along a north-south trend in
eastern Africa.
6. The Great Salt Lake is part of a much larger, Pleistocene lake called Lake Bonneville which
once covered an area of 50,000 km 2 and was as deep as 300 m. Lake Bonneville formed
during pluvial or high-precipitation periods that were the result of glacial stages. Such lakes
shrink during drier interglacial stages like the current stage.
7. Glacial versus interglacial (i.e., cold versus warm) sediment records may be determined by
study of oxygen-isotopic ratios (O18 versus O16) in shells of planktonic marine invertebrates
and (or) by studying changes in relative abundances of foraminifers known to be sensitive to
temperature.
8. The Bering land bridge across the Bering Straight was an important connection between Asia
and America. A 50-meter sea-level drop will cause the land bridge to develop. This event
likely occurred occasionally during Cenozoic.
9. Land-level rise around Hudson Bay, the Great Lakes, and Baltic Sea during historic time is
the result of removal of the last glacial ice sheet (which had down-warped the crust owing to
its weight) and a resultant rebound of land elevation.
10. New and faster, Cenozoic westward movement on the American plate and northward
movement of the Pacific plate caused a lateral fault (strike-slip) boundary to develop in the
San Andreas fault of California.
11. Deposition of a seaward-thickening wedge of clastic sediments many 1000s m thick under
relatively shallow-water conditions indicates profound and continual subsidence during
Cenozoic.
12. The Green River oil shales contain prolific amounts of hydrocarbons and thus are a rich
energy source. They are located at surface or shallow depth and thus easily obtained.
Unfortunately, the mining of such deposits deeply scars and affects the land. Hydrocarbons
are tightly bound in the rock and much energy is required to liberate them. Processing oil
shales is not a clean or efficient operation.
13. Albedo (reflectivity) can be increased by exposing more land surface (as in regression or
deforestation), adding cloud cover or dust/ash content to the atmosphere (as in volcanic
eruptions, great dust storms, or great fires), or adding snow/ice cover. Such changes
generally accompany global climatic change. At the beginning of Pleistocene, sea levels
were significantly lowered and increased snow/ice cover was forming at high latitudes due to
oceanic current diversion.
14. Thick Pleistocene loess deposits formed as cold moist winds flowed toward lower latitudes
from continental ice sheets. The winds picked up fine material from glacial surfaces and outwashed drift and transported it to new sites away from glacial margins. The sediments were
originally soils and pulverized rock entrained by mountain and continental glaciers at higher
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latitudes. The narrow size range of loess particles reflects the wind’s narrow size-range
capacity for moving particles and keeping them suspended for significant times in air.
15. O18, being relatively heavy as compared to O16, is preferentially left behind in sea water upon
evaporation. During cool periods the O18 precipitated in snow does not return to the sea, thus
the sea is enriched in heavy O18. The foraminifers taking oxygen to build their carbonate
(CaCO3) tests do not discriminate between isotopes; therefore their tests are enriched in O 18
during cool intervals.
16. Methane hydrates are cold, sea-floor deposits of methane gas (CH4) that is dissolved in or
trapped in water ice. As methane hydrates melt due to volcanic activity on the sea floor or
global warming effects, the released methane gas breaks down and the carbon in the
methane combines with oxygen in the atmosphere to make carbon-dioxide, a greenhouse
gas.
17. d
18. a
19. d
20. c
Chapter Activities
Student activities for in-depth learning.
1. Using the resources on this page about the Channel Scablands (http://www.uwsp.edu/geo/
projects/geoweb/participants/dutch/vtrips/Scablands0.HTM), describe how these unusual
Pleistocene features formed and their relationship to glacial ice melting. What is the relationship
of the scablands deposits to the Columbia Plateau?
2. Use the web resources of the University of California, Berkeley, Museum of Paleontology web
page on the Green River Formation (http://www.ucmp.berkeley.edu/tertiary/eoc/greenriver.html)
to learn about how that formation was deposited and the types of fossils found there. Describe
these fossils and the environment of the lake during Eocene.
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