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| Major elements in the whole Earth |
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| Major elements in atmosphere |
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| P-waves (compressional) can travel through: |
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| S-waves (shear) can travel through: |
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| ___-waves are faster than ___-waves |
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| P waves are faster than S waves |
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| P and S waves travel faster in ____ materials. |
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| Waves are ____ when the speed changes |
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| There is an S-wave shadow zone because: |
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| S-waves cannot travel through liquid |
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| There is an P-wave shadow zone because: |
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| P-waves travel more slowly through liquid |
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| Material becomes more ____ the closer we get to the center. |
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| When there is a conversion to a more dense mineral structure, the seismic velocity ____. |
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| Why is outer core liquid and inner core solid? |
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| There is more pressure on the inner core. |
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| How did the Earth get layers? |
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| Homogenous accretion (Earth was built of one material and the melting and separation occurred later; molten rock and metal don't mix; molten metal is denser and sinks to the center) |
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| Fe and Mg silicates (olivine and pyroxene) |
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| Earth's mantle has a composition most similar to a: |
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| stony chondrite meteorite |
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| Elements that like to be in a metallic form that go to the core: |
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| Siderophiles (gold, silver, lead) |
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| Elements that fit into the silicate structures that go to the mantle: |
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| Lithophiles (Na, Al, Ti, Si, Mg) |
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| Where did the heat from melting come from? |
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| Heat from impacts and now extinct radionuclides and long lived radionuclides |
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| When did the core and mantle form? |
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Definition
Most likely in the first 30 million years of Earth's history
Core: 182 W/183 W frozen at time of core formation (no more W added since Hf went into the mantle)
Mantle: 182 W increases with time as 182 Hf decays |
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| Who developed the Continental Drift hypothesis? |
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| As you move away from the ridge, the ___ of the ocean increases. |
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| Sediment thickness ______ away from the ridge crest. |
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| Magnetism of young rocks point ____ while rocks older than 750,000 years point _____. |
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| New ocean crust is created at ______ ______, which crust moving away from the ridge (seafloor spreading) |
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| When were South America and Africa joined as one continent? |
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| 120,000,000 years ago (120 million years) |
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| What is the underground movement of two pieces of rock relative to each other along a fault plane? |
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| If seafloor is created at ridges, then it is destroyed at ______ zones, which occurs are ______ boundaries. |
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| Outer rigid shell of the earth (contains crust and and rigid part of the mantle) |
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| Part of mantle beneath the lithosphere (moves as a fluid) |
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| Volcanoes occur at _____ and ______ plate boundaries. |
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| Earthquakes occur at ______, ______, and ____ boundaries. |
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| divergent, convergent, strike-slip |
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| Mountain belts are built at ____ boundaries. |
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| Ocean crust forms at _____ plate boundaries. |
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| What drives plate motion? |
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| Crust travels from spreading center where it is created to a subduction zone where it is destroyed |
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| What does isostatic compensation of continents and ocean crust prove? |
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| The upward buoyant force on an object is equal to the weight of the displaced fluid |
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| Density contrast in a fluid |
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| What inhibits convection? |
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| High viscosity (then the heat will be transferred by conduction) |
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| What contributes to convection (high Rayleigh number)? |
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| high coefficient of thermal expansion, high gravitational constant, large temperature difference between top and bottom, low viscosity, low thermal conductivity |
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| Where ridges migrate away from each other. |
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| Plate movements cause local _____ at ridges and major _______ at subduction zones. |
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| What helps drive plate motion? (when high pressures converts basalt to eclogite, which has a higher density than the surrounding mantle, which makes the slab dense and pulls it to the bottom) |
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| Intra-plate (hot spot) volcanism reflects: |
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| Hot spots are _____ ______ rising beneath the plate at a single point. |
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| Subduction zones correspond to _____ in mantle convection. |
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| _____ crust is old and thick (30 km) and ______ crust is young and thin (5 km). |
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| Continental crust is made of _______ and ocean crust is made of __________. |
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| Granite (quartz, feldspar, mica); basalt (olivine, pyroxene, feldspar) |
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| First partial melt of the mantle creates: |
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| Fe, Mg, Si, O plus Na, Ca, Al, and more Si, O (which is ocean crust!) |
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| Large ions incompatible with olivine and pyroxene structure that go into the melt: |
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| How to get the mantle to melt: |
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| Shallow, thick ridges are formed over ____ spots; deep, thin ridges are formed over______ spots. |
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| More melting at a higher temperature correlates to low _____ and ______ depth, |
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| How is continental crust formed? |
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| Partially melted ocean crust (get even higher concentrations of large ions that don't belong in olivine and pyroxene, which creates pink feldspar) |
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| Ocean crust is ______, while continental crust is ______. |
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| Large ion concentration would be highest in ______ crust, then _______ crust, then the _______. |
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| continental; oceanic; mantle |
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| Large ion concentrations are higher in _____ oceanic crust forming over _____ spots. |
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| thin; cool (large ions are not happy in the mantle so they want to go into the melt ,so the higher the temperature, the more that melts, and the lower ion concentration is) |
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| Most abundant elements in universe: |
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| Most abundant elements on Earth: |
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| Most abundant elements in life: |
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| Most abundant elements in atmosphere: |
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| Gases are more likely to escape in a ______ atmosphere. |
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| Escape velocity is _____ for smaller planets. |
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| ______ gases are more likely to escape. |
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| _____ planets are better able to retain an atmosphere. |
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| Origin of ocean and atmosphere: |
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-Volatiles trapped in solid minerals; released during core/mantle
-Late arriving carbonaceous chondrites (ordinary chondrites contain enough water to fill four oceans)
-Late arriving comets |
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| _____ isotopes indicate that much of the early atmosphere may have been lost to space when H2O was steam |
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| _____ molecules have a higher average speed than _____ molecules. |
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| Most of the carbon on Earth is in ________. |
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| What helps keep the atmosphere's oxygen content within a narrow range over geologic time? |
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- At high oxygen levels, organic matter spontaneously combust
-At low oxygen levels, burial of organic carbon in the ocean will increase.
-At high oxygen levels, burial of organic carbon in the ocean will decrease. |
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| Long-term fluxes of carbon to and from silicate rock reservoir provide a negative feedback that stabilizes earth's climate because |
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| increased temperatures lead to increased weathering rates |
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| The faint young sun paradox is resolved because |
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| early earth was likely to have more greenhouses gases in the atmosphere. |
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| A self sustained chemical system capable of self0replication and evolution. |
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| Why is carbon important to life? |
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-Has 4 electrons missing from outer shell, which allows for reactions that allow energy flow and storage
-Can form molecules that are solid, liquid, and gas at the temperatures of liquid water |
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| Built amino acids. Proved that it would take a specialized environment (deep sea vent) to create them on Earth. |
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| Cell membranes consist of a ____ bi-layer. |
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| To build nucleic acids, a _______ can help concentrate ingredients. |
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| What is easy to make in the lab from inorganic chemicals? |
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| First type of life t get energy from sunlight (photosynthetic): |
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| cyanobacteria (blue-green algae) |
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| Types of rocks that cool from melt |
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| Type of rocks that are weathered particles |
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| Type of rocks that are deformed at high temperatures and pressure |
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| Organic matter has low_____/______ levels. |
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| The presence of life makes the ratio of 13C/12C in carbonate rocks higher than the ratio in bulk earth because organisms: |
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| preferentially take up the heavier isotope (13C) |
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| What fossil evidence do we have of earliest life? |
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Cells- 3.5 bya
-Stromatolites- 3.5 by a |
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| What chemical evidence do we have of earliest life? |
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| Banded iron formations appear at 3.5 bya |
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| _________ _________ _________ required anoxic ocean and atmosphere (so Fe can dissolve in seawater) and O2 gas in some isolated environments (to precipitate Fe oxides, Fe2O3) |
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| Controls on atmospheric oxygen: |
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-process which produce oxygen (photosynthesis)
-processes which destroy oxygen (consumption by oxidation of minerals/volcanic gases/organic material) |
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| 3.5-2 bya: All oxygen produced by photosynthesis is consumed by oxidation of minerals |
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| All oxygen produced by photosynthesis is consumed by oxidation of minerals |
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Minerals at earth's surface are saturated with oxygen and O2 builds up in atmosphere (evidence: red beds are rocks with oxidized iron minerals)
And eucaryotic cells develop |
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| final rise to today's oxygen levels. first animals appear. |
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| Why does the presence of banded iron formations between 3.5 and 2 bya require the presence of life in the ocean? |
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| Because iron precipitates from seawater in the presence of oxygen gas |
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| Why does the presence of BIF require an oxygen poor atmosphere? |
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| Because iron dissolves in seawater in the absence of oxygen |
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| What supports the idea that O2 gas started accumulating in the atmosphere after about 2 bya? |
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-BIF no longer form after 2 bya
-Redbeds appear after about 2 bya
-Eucaryotic cells appear at about 2 bya |
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| Objects with lower temperatures emit electromagnetic radiation with _______ wavelengths than objects with higher temperatures. |
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| An object with a radius twice the size of another object will emit energy ______ times as fast as the other object. |
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| 4. (radius squared; bigger objects emit more energy) |
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| The rate at which energy emitted by the sun/area over which this energy is spread |
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| Flux ________ with distance from the sun. |
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| Solar radiation is _______ radiation, while infrared Earth radiation is _________ radiation. |
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| Energy absorbed by the earth is the ______ at the distance of the Earth's orbit x cross section of the Earth |
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| Incoming energy from the sun is determined by ________ parameters and _______ of the sun. |
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| orbital parameters and temperature of the sun |
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| The temperature at the surface of the earth will be reached such that _______ in= ________ out. |
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| A planet that is 5 times as far as another planet from the sun absorbs energy from the sun __________ times as fast as the other planet. |
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| 1/25 (1/distance squared) |
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| A planet that is 5 times as far as another planet from the sun emits energy back to space __________ times as fast as the other planet. |
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| 1/25 (1/distance squared) |
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| Reflectivity of the sun on earth |
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| What contributes to albedo? |
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| Clouds, ice, snow, aerosols, volcanic SO2 |
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| When outgoing infrared radiation is observed by the atmosphere and re-radiated both out to space and back down to the ground |
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| Water vapor (most important), CO2 (rarer, but effective at trapping radiation), methane, N2O, ozone |
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| The earth's surface is warmer than earth's temperature as seen from space because |
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| the energy emitted from earth's surface must balance incomings shortwave radiation from the sun and incoming long wave radiation from the atmosphere (greenhouse effect) |
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| Two ways to change earth's surface temperature: |
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1) Change energy absorbed by sun
2) Change amount of greenhouse gases |
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| Process in which perturbation causes system to travel further away from initial state |
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| What stabilizes earth's climate? |
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| Long term CO2 regulation by weathering and volcanism |
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| What removes CO2 from the atmosphere? |
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1) Chemical weathering
2) Plants and animals that form hard shells |
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| What puts CO2 in the atmosphere? |
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1) Volcanism (when shells made of carbon are subducted, the carbon is released through volcanoes.
2) CO2 enters atmosphere faster when plate tectonics move faster |
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| CO2 is removed faster from the atmosphere when _______ on continents is higher. |
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| Early in earth's history, there were probably more greenhouse gases (methane) that kept a role in keeping the earth warm |
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| The high ratio f 2H/H in Venus' atmosphere tells us that: |
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| much of the water escaped as steam, which is why carbonates cannot form on Venus |
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