EAS Final
Which of the following is evidence that Neoproterozoic glaciations occurred at sea level?
Dropstones
How do we know that the glaciers occurred at low latitude?
Magnetic materials are parallel to bedding planes in sed. rocks w/ dropstones
Which is not a possible contributing factor towards the freeze-down?
More volcanism
How did the earth escape the snowball?
Weathering decreased, allowing CO2 to accumulate
Fossil bivalves (e.g. clams) are much more abundant than fossil worms. Which is the least likely reason for this?
Clams are more abundant than worms
Which of the following is not used date the sedimentary rocks which contain fossils?
The decay of radionuclides in the sedimentary rocks
The polar bears are a relatively recent species, only diverged from brown bears about 250,000 years ago. The polar bears hunt on Arctic sea ice and brown bears hunt on land. Which of the following is not likely to be true:
Polar bears and brown bears routinely interbred
Members of the animal phylum Priapulida have hard parts. When did this phylum first appear in the fossil record?
550 mya
What increases as specialists gradually replace generalists?
Diversity
What is the extinction rate over time?
0.00001% per year for species
How many mass extinctions have there been over time and what were they?
5: Ordivician, Devonian, Permian, Triassic, Cretaceous
What are potential causes for mass extinctions?
Extraterrestrial impact, intense volcanism, ecological catastrophe, continental drift/sea level drop, habitat loss, global cooling/glaciation, ocean anoxia
Extinctions of species occur how often?
All the time
How can volcanism lead to mass extinction?
Short term cooling (particulates in atmosphere help reflect sunlight back to space), acid rain (sulfur released from volcano), longer term greenhouse effect
What were the causes of the End Permian Extinction?
Two pulses of massive volcanism, which caused?:
1) Short term cooling
2) ?Carbon release from volcanism and from coal beds
3) Global warming
4) Ocean acidification
5)Ocean stratification and anoxia

or a meteor caused it

What are three ways that volcanism can cause mass extinctions?
1) Changing the atmospheric CO2 content
2) Making acid rain
3) Changing the earth’s climate
Three facts about the Permian mass extinctions:
1) Ocean chemistry changes could have played a role
2) The evidence for an extraterrestrial impact is controversial
3) A larger percentage of species went extinct than during the Cretaceous/Tertiary extinction
What is evidence for the impact at the K-T boundary?
1) Iridium anomaly: there is 60x too much iridium at boundary– can’t be explained by slow down in sedimentation.
2)Platinum, gold, silver were also enriched, and ratio was the same as in meteorites
3)The isotope ratio of 187Os/186Os is greater in the crust than it is in meteorites, and then ratio in KT boundary is closer to the ratio in meteorites than the crust.
4) Spherules and microtectites were found in the boundary, as well as shocked quartz grains
5) Impact crater (Yucatan peninsula).

Meteorite was probably 10-15 km in diameter

If we know that Pb is a siderophile element, then we know that:
Pb is enriched in ordinary chondrites relative to the earth’s crust
How is material spread around the globe after a meteorite impact?
1) Heat from impact vaporizes liquids and solids
2) Drop in density causes shock wave (explosion)
3) Atmosphere gets less dense with height, so material will rise and spread until it is at the level where the atmosphere is the same density and then it will condense and fall back to earth
4) Large particles enter low orbits around earth and then fall back down
5 ways that a meteorite impact would cause a mass extinction:
1) Global darkness, which would kill the bottom of food chain (plants) and make the earth cold
2) Water vapor would cause greenhouse warming
3) Carbonate would become vaporized and cause green house warming
4) Acid rain: kills plants, poison surface of ocean
5) Global fire
Two ways that meteorite impacts and volcanism correlate to cause extinction:
1) Impacts/extreme volcanism occur randomly, but when they coincide, we get severe extinctions
2) Impacts trigger extreme volcanism, which exacerbates the effects of impact on life
Evidence for Mid-Cretaceous (100 mya) Warmth:
1) Land Fossils: Ferns, Crocodiles found in Siberia
2) Distribution of coal and evaporite deposits
3) High sea level- may re?ect small or non-existent glaciers.
4) Oxygen isotope ratios in carbonate shells
What is evident about the Cretaceous period from the rock record?
1) It was warmer than today near the poles and temperate latitudes (but not tropics necessarily)
2)? Warm fauna and flora were found at higher latitudes than today
When shells form they discriminate against:
18O (Oxygen)
High 18O/16O in shells implies _____ temperature, because they discriminate against 180 less in ______ water.
cold temperature
Low 18O/16O in shells implies _____ temperature, because they discriminate against 180 less in ______ water.
warm temperature
Low 18O/16O ratios of planktonic foraminifera in the Cretaceous tropics tell us that:
The tropics were warm
Low 18O/16O ratios of benthic foraminifera in the Cretaceous tropics tell us that:
High latitudes were warm
Why was the mid-Cretaceous era warm?
Higher CO2 levels in atmosphere caused by either:
1) Indirect evidence: Faster rates of sea?oor spreading -> faster rate of CO2 input into atmosphere -> higher atmospheric CO2.
OR
2) Independent con?rmation from carbon isotope ratios of CaCO3 precipitated in ancient soils.
How did we determine the atmospheric CO2 levels using the Paleosol Method?
1) 12C (99%) and 13C (1%) are stable isotopes of carbon
2)The process of photosynthesis discriminates against 13C when taking CO2 from the atmosphere and incorporating the carbon into organic material (CO2 + H20 -> CH2O)
3)? Organic matter of land plants has lower 13C/12C than the ratio in the atmosphere
4) Plant organic matter (roots, fallen leaves) decays within the soil (CH20 -> CO2 + H2O), releasing CO2 that is low in 13C/12C
4) Atmospheric CO2 also diffuses into the soil
5) If atmospheric CO2 concentrations are high, the 13C/12C in soil CO2 is close to the atmospheric ratio
6) If atmospheric CO2 concentrations are low, the 13C/12C in soil CO2 is close to the organic ratio
7) CaCO3 precipitating in soils records the 13C/12C in soil CO2
A high ratio of 13C/12C in soil gas as recorded by soil carbonate minerals reflects:
A high proportion of carbon from the atmosphere
What is the stomata density method?
1) Stomata are holes in the leaf of a land plant where CO2 enters (CO2 + H2O -> CH2O)
2) Plants also lose water through their stomata
3) When atmospheric CO2 is higher, the plant needs fewer stomata, so we can tell the number of stomata from fossil records, which indicates the level of atmospheric CO2
Leaves have fewer stomata when atmospheric carbon dioxide levels are high
So they will lose less water
Glaciers happen when
snow turns into ice over land
Evidence of glaciation:
1) Grooved/polished surfaces
2) Unsorted sediments (till)
3)Dropstones in marine sediments
How do we have a continuous record of glaciation from oxygen isotopes?
1) H2/16O evaporates more readily from the ocean than H2/18O
2)Snow (which forms when vapor condenses) will have a lower 18O/16O ratio than the ocean
3)Glaciers will have a lower 18O/16O than the ocean
4) The more water locked up in glaciers, the higher the 18O/16O of the seawater left behind
During the Cretaceous there were no continental ice sheets. The ratio of 18O/ 16O in sea water was _______ than today.
lower
There is ______ oxygen (18O) in water, and ______ oxygen (16O) in ice sheets.
heavier in water, lighter in ice
Higher 18O/16O in seawater, _____ 18O/16O in shell; Lower 18O/16O in seawater, _____ 18O/16O in shell given the same temperature.
Higher/lower
During the Cretaceous the ratio of 18O/16O in sea water was .3% lower than today. Tropical temperature was the same as today. The ratio of 18O/16O in tropical planktonic foraminifera was
.3% lower than today
What causes glacial cycles?
-Tilt of the earth’s axis could contribute (Milankovitch’s theory)
________ is when the hemisphere you are in is tilted towards the sun
Summer
To build ice you need a _____ winter and a _______ summer.
warm winter/cool summer
To create a warm winter/cold summer, you need 3 things:
-Low tilt angle (happens every 41,000 years)
– Precession such that winter occurs when earth is closest to sun (every 23,000 years)
-Elliptical orbit (precession will not affect the climate if the orbit is circular)
If you want an ice sheet to grow in the Northern Hemisphere the earth’s axis should be more:
Upright (low tilt angle: warm winter/cool summer)
If you want an ice sheet to grow in the Northern Hemisphere, the Northern Hemisphere summer should occur at:
Aphelion (the place farthest from sun on earth’s orbit) (which creates a cool summer)
If you want an ice sheet to grow in the Northern Hemisphere the earth’s orbit should be
More elliptical
Seasonality has around _____ year cycles
23,000
Large deglaciations correspond to _____ Northern Hemisphere summers.
warm
Ice sheets _____ more quickly than they _____.
decay than grow
If orbital cycles drive glaciation why do southern hemisphere glaciers expand at the same time as northern hemisphere glaciers?
Land mass in northern hemisphere are at latitudes that are sensitive to precessional forcing.(Antarctica is already full)
Evidence for lower temperature on land:
1) Mountain glaciers at low latitudes descended 1 km, indicating cooling
2)Noble gasses in groundwater indicate cooling in tropical/temperate regions
3) Vegetation ranges shifted toward equator (recorded in pollen from lake sediments)
Henry’s Law: (4 things)
1) Gases are soluble in liquid
2) Gases are always moving across the gas-liquid interface
3) At equilibrium, the concentration of the gas in solution is proportional to the pressure of the gas in the overlying space
4) Solubility is specific for each gas and generally increases with decreasing temperature
Water that has equilibrated with the atmosphere at cold temperatures contains:
more gas
Water that left the earth’s surface 20,000 years ago has more Xe than surface water today because:
Gas solubility increases at cold temperatures
If you change the rate of sea floor spreading it would take _______ years for the carbon in the fast pool to respond
800,000
The exchange of carbon between ocean/atmosphere/plants/soil is called:
fast pool of carbon
We know from ice cores, that atmosphere had less carbon in the last ice age, and we know from pollen/ice sheets that land had less carbon, which means that the _____ must have had more carbon.
ocean
Ocean-atmosphere carbon equilibrium:
1) Glacial ocean was cooler: solubility of CO2 increased in the ocean and reduced the CO2 in atmosphere
2) Glacial ocean was saltier: decreased the solubility of CO2 in the ocean and raise the CO2 in the atmosphere
Amount of carbon in atmosphere depends on: (3 things)
1.How much of the surface ocean carbon is CO2 (gas)
2. How cold the surface ocean is
3. How salty the surface ocean is
What determines partitioning of carbon between surface and deep waters?
1)Carbon pumps create a carbon gradient between surface and deep ocean
2) Mixing deep and surface waters only partially erases this gradient
Solubility pump:
1) Water equilibrates with atmosphere at surface
2) Deep waters equilibrated with atmosphere at cold temperatures
3) Gases are more soluble in cold waters
4)Deep waters have more carbon
Biological pump:
1) Organisms take up carbon during photosynthesis in the surface ocean
2)When they die they sink into the deep ocean
3) Carbon is returned to seawater when organic material is broken down
If the temperature of the ocean decreases, atmospheric CO2 concentration:
decreases
If the ocean biota went extinct, atmospheric CO2 concentration would:
Increase (the biological pump goes away — biota take CO2 from the atmosphere)
If the mixing between surface and deep waters decreases, atmospheric CO2 concentration:
Decreases
(Mixing erases the gradient. Less mixing –> carbon pumps bring more CO2 down to the bottom –> less atmospheric CO2
Ice ages are paced by changes in:
earth’s orbit
Global cooling during ice ages is a result of:
reduced atmospheric CO2 (which is a consequence of more carbon in the deep ocean by the biological carbon pump)
What is the main reason the global temperature is lower 20,000 years ago relative to 2,000 years ago:
Atmospheric CO2 was lower 20,000 years ago
Where did all hominid species originate?
Africa (7 million BC)
How do we know that early hominid species spread to Eurasia?
fossil evidence
Where and when was the first fossil evidence of modern homo sapiens found?
-Africa: 160,000 years ago
-Outside Africa: 50,000 years ago
Given enough time, a population will have a common ______ ancestor.
maternal
Humans with more similar __________ DNA have more recent common ancestor, because mutations accumulate in the DNA of ___________ at a set rate.
Mitochondrial; mitochondria
The DNA in your mitochondria is almost identical to you biological _______.
mother’s
The fact that there is less genetic diversity among Europeans, Asians and Americans than among Africans:
supports the idea that modern humans from Africa replaced earlier hominid species on other continents
Type of hominid that used tools and fire, and existed until at least 18,000 years ago:
homo florensis
What caused American megafauna (large mammals) extinctions?
Arrival of humans (overkill from hunting)
How dod we know that megafauna extinctions were caused by humans and not climate?
1) Megafauna survived other climate transitions
2) No climate transition associated with Australian extinctions
3) Extinctions were less severe in Africa where humans and megafauna co-evolved
What percent of species on islands have gone extinct within the last 500 years?
90%
What evidence does not support the idea of human induced megafauna extinctions?
European megafauna extinctions at 10-12 kyr (?)
If we wanted to restore the North American ecosystem to close to its natural state we should
establish bison and grizzly bear, and elephant and llama populations (?)
For every ____ in the atmosphere, there is one _____ in sediments.
Oxygen; carbon
______ release energy when we find the reduced carbon in organic matter and burn it.
Fossil fuels
The earth’s atmosphere contains 3.75 x 10^19 moles of O2 gas. How many moles of organic carbon are stored in the earth’s sediments and rocks?
3.75 x10^19 moles (the same amount)
Low 02 environments:
1. Swamp/bog (so much decaying organic material that water becomes anoxic)
2. Anoxic ocean/sea (Organic matter falls to seafloor, oxygen is consumed and CO2 is produced, and once O2 is gone, organic matter is no longer oxidized and is buried)
Burial of ocean sediments is enhanced by: (3 things)
1) High flux of organic matter to sediments (more C to be buried, O2 used up fater)
2) Low bottom water O2 (O2 used up quickly with smaller amount of C oxidation necessary to use O2)
3) High sedimentation rate (C buried deeper more quickly, harder for more O2 to diffuse into sediments from overlying seawater)
_____ patterns cause upwellings of deep water to occur in a few places where biological activity is the highest, and therefore biological debris accumulates below these zones.
Wind patterns
Chlorophyll has higher productivity and higher sedimentation rates near:
continents
The organic carbon content of ocean sediments accumulating on the mid-atlantic ridge is low because:
The rates of sediment accumulation is low
Coal is made from decayed ____ matter in _____.
plant matter in swamps/bogs
What is the solid, waxy, organic material, made from compact mud with organic matter, that is not a useable fossil fuel?
Shale with kerogen
What is made after shale is buried and heated (has large molecules and is viscous)?
Tar, petroleum jelly, paraffin
What is made when tar, petroleum jelly, are heated at even higher temperature (smaller molecules, less viscous)?
diesel oil, kerosene, gasoline
What is made when oil, kerosene, gasoline are heated to 100 degrees, and the liquids break down (smallest molecules)?
Gases: propane, ethane, methane
Where can you get hydrocarbons? (3 places)
1) Source rocks (fine grained rocks formed from organic rich mud)
2) Reservoir rock (nearest porous rocks)
3) Cap rock: (Oil migrates upwards until trapped by impermeable rocks)
What percent of buried plant material becomes useable petroleum?
Less than 0.1%; not hot enough, not buried deep enough, no appropriate trap
Natural gas forms at higher temperatures than _________.
oil
As fossil fuels are extracted and burned, ____ increases, _____ decreases.
CO2 increases, O2 decreases
If we burn all of the available fossil fuel, atmospheric oxygen will decrease by:
less than 1%
More expensive types of fossil fuels: (4)
1) oil shale
2) tar sands
3) shale gas
4) Methane in deep sea sediments (stored as methane hydrate)
How do we know that atmospheric CO2 concentrations have been rising since 1800?
CO2 is measured in air trapped in polar snow and ice
1 Petagram (Pg)= 1 _____ metric tons = 1 gigaton
billion; gigaton
1 Teragram (Tg)= 1 _____ metric tons
million
1 kg of carbon = _______ kg of carbon dioxide
3.67
Sources of CO2 in the atmosphere: (4)
1) Coal: 43%
2) Oil: 34%
3) Gas: 18%
4) Cement: 5%
Only _____ % of CO2 can be found in the atmosphere
40-45%
____ _______ will absorb some of the extra CO2, and it will take approximately 1 month for it to equilibrate with the atmosphere
surface ocean
Water exchange between surface and deep ocean takes around ____ years, so the rate of ocean mixing will determine how fast the CO2 is absorbed into the ocean
500
Approximately ____ % of fossil fuel CO2 emissions is absorbed by the atmosphere, ___ % is absorbed by the biosphere through fertilization, and _____ % is absorbed by the ocean.
50;26;24
Timescale for neutralization of fossil fuel CO2:
-70% will diffuse into deep ocean in 500 years
-20% will be absorbed into ocean sediments in 5000 years
-10% will be drawn out of the ocean/atmosphere by chemical weather in 1 million years
The CO2 that has been released into the atmosphere over the last decade from the burning of fossil fuels and from the destruction of forests and soils can be found:
in the atmosphere, ocean, and biomass/soil (?)
The extra atmospheric CO2 from the burning of fossil fuels will be 99% gone in
5 million years (?)
Effects of increased greenhouse gases: (6)
1) Direct temperature increase from trapping longwave radiation close to earth
2) Indirect temperature increase from feedbacks (water vapor/cloud/snow-ice albedo)
3)Storm patterns/more intense hurricanes
4)Precipitation patterns (wetter wets and drier dries)
5) Sea-level rise (expansion of ocean/melting glaciers)
6) Changes in patterns of vegetation/habitats of animals
The warming observed over the past 2 decades is mostly a result of:
increased greenhouse gases (?)
Which of the following is not a projected impact of increased of atmospheric CO2?
Increased incidence of tsunamis (?)
Exponential growth:
amount added with time proportional to how much there is. Characterized by constant doubling time
The human population until 1970’s was ____, but since the doubling time has ______ with time.
exponential; decreased
_____ systems reach carrying capacity smoothly.
Simple
_____ systems’ populations oscillate about the carrying capacity.
Complex
Most estimate that the human carrying capacity is around ____ billion people.
12-15
The carrying capacity critically depends on:
finding alternative energy resources
Estimated timescale for the future:
____ years- global human population stabilizes
________ years- atmospheric CO2 recovers from fossil fuel release
_________ years- head into another ice age
________ years- a meteorite more than a km wide will probably strike the earth
________ years- there will be a super continent at the equator
______ years- 10% more solar luminosity will cause the CO2 thermostat to break and the oceans will evaporate
_____ years- Milky way collides with Andromeda
_____ years- Sun finishes H burning phase and becomes red giant (500 x more luminous)
_______ years- Sun dies (fusion done)
100 years- global human population stabilizes
5000 years- atmospheric CO2 recovers from fossil fuel release
50,000-200,000 years- head into another ice age
10,000 years- a meteorite more than a km wide will probably strike the earth
25,000,000 years- there will be a super continent at the equator
1.1 billion years- 10% more solar luminosity will cause the CO2 thermostat to break and the oceans
3 billion years- Milky way collides with Andromeda
6 billion years- Sun finishes H burning phase and becomes red giant (500 x more luminous)
-7 billion years Sun dies (fusion done)
Describe how we know that the atmospheric CO2 was lower by 100 ppm during the full ice age?
Pockets of air in ice cores
Was the biological pump likely stronger or weaker during the ice age?
Weaker (apparently because there was less plankton, although this answer doesn’t really make sense because there was less atmospheric CO2 during the ice age but a weaker biological pump increases the amount of atmospheric CO2)
Early hominid species were present in Africa:
4 million years ago
Modern humans in Asia descended from
modern humans that left Africa 50,000 years ago.
The tiny skeletons found on the island of Flores are from individuals that are thought to be:
descended from early hominid species
Ground sloths inhabited North America starting 9 million years ago. They disappeared:
10,000 years ago due to the arrival of humans in North America
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