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103 Cards in this Set
- Front
- Back
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What is geology? |
Study of the Earth |
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What is planetary geology? |
The extension of geology to other worlds, including moons, asteroids, etc. -Aim is to understand what processes shape planetary surfaces |
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How can we infer the density structure of Earth's interior? |
Seismic waves - vibrations that travel through the Earth's interior and along its surface |
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What is the structure of the Earth's interior? |
Least dense --> Most dense (all terrestrial planets show this similar structure) 1) Crust 2) Mantle 3) Inner Core (Earth, Venus, and Mercury all have relatively the same size core --> but Mercury has relatively large core compared to its mantle) |
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What causes the density layering seen in the terrestrial planets? |
Differentiation! - gravity causes the denser liquids to sink toward the center (hotter/lighter materials rise) |
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All terrestrial planets show evidence for differentiation: they have metal cores. This implies that? |
Temperatures must have been high enough to melt metals. (so at some points, all planets were hot enough to melt metal!) |
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What does the heating process do? |
Converts energy (kinetic, potential, or mass-energy) into thermal energy. |
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What are the 3 types of heating processes? |
1) Accretion - impacts (gravitational potential energy converted to kinetic, converted to thermal) 2) Differentiation 3) Radioactive Decay - mass energy in nuclei converted to thermal |
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What are the 3 types of cooling processes? |
1) Convection (hot stuff rises, cold stuff sinks) 2) Conduction (carries heat out of surface) 3) Radiation (energy is radiated into space) |
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How did the planetary interiors INITIALLY heat up? (the cause of the density differentiation found in terrestrial planets) |
Hot enough at one point to melt metals b/c of: 1) Differentiation 2) Accretion |
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What is the main source of heating in terrestrial planets today? |
Radioactive decay of nuclei |
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What is geological activity? |
Changes on the surfaces of planets due to internal HEAT activities (volcanoes, earthquakes..) |
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How did the Moon and Mercury's surfaces look a long time ago? |
Same as now...they are geologically "dead" |
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What are the four major processes that alter planetary surfaces? |
1) Impact cratering 2) Volcanism 3) Tectonics (only Earth has plate tectonics) 4) Erosion |
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What are impact craters? |
When a planet collides with an asteroid or comet -creates an impact 10 times as big as object -more small craters than big -large impacts linked to dino extinction -craters exist on ALL terrestrial planets |
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Why does the moon have more impact craters than the Earth? |
The Earth's atmosphere burns up the objects before it reaches the surface |
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Are there more crater impacts now or before? |
Most during heavy bombardment period (lots of planetesimals at that time, so more impacts) |
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What can we learn from counting the number of craters on the surfaces? |
Can tell the age of planetary surfaces I) Heavy cratering = old (highlands) II) Light cratering = young (mare) |
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You compare two different regions on a planet. One has many craters, the other has far fewer. What can you conclude? |
They both must have experience roughly the same number of impacts, therefore some other process must have masked some crater in the region that shows fewer impact craters! |
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What is volcanism? |
Any eruption of lava (molten crust) onto the surface of a planet |
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How do we differ different types of volcanism? |
By their thickness of lava |
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What are the three types of volcanism? |
1) Volcanic Plains - lava flattens out before solidifying 2) Shield Volcanoes - solidifies before it completely spreads out (can be tall but not steep) 3) Stratovolcanoes - can't flow far before solidifying (tall/steep) --> tend to only be found on Earth |
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What is the largest volcano in the Solar System? |
Shield Volcano on Mars (Olympus Mons) |
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What is Tectonics? |
Surface reshaping resulting from stretching or compression of the crust |
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What is Erosion? |
Processes that break down or transport rock through action of ice, liquid or gas Ex. dunes shifted by wind, valleys created by glaciers |
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What is the "geological age" of a planetary surface? |
Not the planets age! Different parts of the same planet can have different geological ages |
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How do we determine geological age? |
Counting craters (lots of craters, not much has happened since heavy bombardment - therefore geologically older) -chronometers |
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The Moon - which two very distinct surfaces are found here? |
1) Lunar Highlands (light zones) - more heavily cratered 2) Lunar Maria (dark zones) - geologically younger |
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Is the near or far side of the moon more heavily cratered? |
Far side |
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The lunar highlands show more craters than the lunar maria, this means that... |
The lunar maria cover older impact craters |
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Difference between determining age from crater counting and radiometric dating? |
Crater count - relative age Radiometric dating - absolute age (highlands 4.4. billion years old, maria 3 - 3.9 billion years old) |
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Why study moon impact craters? |
Heavy bombardment must have been the same for all terrestrial planets...impact rates of the moon should be the same as other terrestrial planets |
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What types of processes alter the surface of the moon? |
Volcanism (maria - volcanic plains), some tectonic features (generally in maria), impact craters |
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When did lava fill up the impact craters that are now the lunar maria? |
Few 100 Millions of years after the impact (due to moon's small size, it cooled down fairly quickly - decay of radioactive elements heated mantle enough to melt rocks into lava) |
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Surface features found on moon? (Moon's tectonic features) |
-Volcanic rilles (lava tubes)
Moon's Tectonic Features: -Wrinkle ridges (lava plain shrinks/cools/contracts, rock buckles up) -Graben(dip)/Horst(bulge) (formed under extension stresses)
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Present-day activities on the sun? |
Sandblasting - micrometeroites impact soil and pulverize rocks resulting in moondust (very abrasive that erodes crater rims - big issue for astronauts)
For the most part the moon is "geologically dead" - no recent activity |
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Mercury's geology? |
-least studied (MESSENGER helping now - but nothing has landed on mercury before) -surface is similar to moon (craters less crowded together, fewer molten lava plains cover craters, small volcanic plains) -huge impact crater reverberated throughout planet and jumbled crust on opposite side
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Mercury's Tectonics? |
Mercury's core and mantle shrank...causing crust to contract (some of the crust slid under others - created steep cliffs) - shrinkage of entire planet! |
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Geological activity on the Moon and Mercury stopped long ago. This is mainly because? |
They are small (small planets cool faster, so not enough interior heat left to produce volcanism or tectonics) |
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Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If true, which of these could explain it? |
The higher surface temp has "baked out" all the liquid water from Venus's crust and mantle |
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What does Mars's surface look like? |
-Fewer craters than Moon or Mercury (more geologically active since it is bigger) -Southern hemisphere more heavily cratered than Northern |
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Mars' Southern hemisphere shows heavily cratered highlands while the northern hemisphere shows plains and fewer craters. This means that? |
The southern hemisphere is a much older surface than the northern hemisphere |
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What geological processes are found on Mars? |
Volcanism (lava plains erase craters in N plains/ Olympus mons), tectonics, erosion, and impact cratering |
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What is the Tharsis bulge on Mars? |
A large region of elevated terrain (caused by magma plume rising up and pushing the crust up) |
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Are there any active volcanoes still on Mars? |
-Crater counts - inactive for 10's of millions of years -possibly recent activity less than 2 million years ago though |
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Tectonics on Mars? |
-Most prominent feature is Valles Marineris (rift valley) |
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Evidence for Erosion on Mars? |
Water and wind processes -lots of evidence that Mars had liquid water on its surface in the past! (canals-river beds on mars, impact of muddy ground, possible flash floods) -water erosion likely doesn't exist now, too cold for liquid water, and atmospheric pressure would prevent liquid water from existing for a long time |
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Evidence of Martian Blueberries? |
Spherules made of hematite (can be formed of water...but other formation mechanisms also possible) |
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Evidence of Goethite on Mars? |
Can only be formed in water!!! |
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If water isn't still on Mars, where has it gone? |
-Rainfall era ended 2-3 billion years ago -large portion lost in space -some deposits still present as ice (large subsurface water ice deposits) |
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What causes wind erosion on Mars? |
Atmosphere on Mars causes wind erosion (from dust storms, dust devils) - slowly eroding polar caps |
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Compared to Mars, I would expect Venus to show... |
Fewer impact craters (uniformly distributed - surface about the same age over entire planet- young about 750 million years old), more volcanism (all 3 types), and more tectonics (very little erosion)
-no small craters - smaller meteorites burn up in thick atmosphere |
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Volcanism on Venus today? |
-Probably still active (sulfuric acid in atmosphere; 10 fold drop in sulfur dioxide - indicative of active volcanoes) |
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Tectonics on Venus? |
Coronae - mantle plumes that push up the crust (stretch marks on surface) --> thought that Venus baked water out of crust, so crust is much stronger and heat cannot escape |
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Is there erosion on Venus? |
-Only minor (too hot for liquids like water or ice, no wind either due to slow rotation of Venus) |
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What geological processes are present on Earth? |
-All 4 + plate tectonics (only terrestrial planet - contributes to stability of our climate) - many impact craters have been erased by glaciers |
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Evidence for plate tectonics on Earth? |
-Continental drift -Seafloor spreading -Seafloor crust (recycled more often through subduction - 200myo) and continental crust(4 byo) -Subduction zones (ring of fire) |
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What's an atmosphere? |
Layer of gas surrounding a planet -generally very thin (2/3 of air in atmosphere is within the lowest 10km) |
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What is an atmosphere good for? |
-Determines temperature and overall climate of planets -where weather happens -we breathe atmosphere -protects us from dangerous radiation -determine whether water can exist in liquid form on a planet's surface |
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How are atmosphere's characterized? |
By their 1) Chemical composition, and 2) Pressure at the surface (how much gas) |
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What is chemical composition? |
The relative amounts of different gases that are found in the atmosphere |
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What is surface pressure? |
-The atmospheric pressure at the planet's surface (the weight of the atmosphere per square meter) -measured in pascals (1 bar = 1 atmosphere pressure at Earth's surface) -Higher pressure means more weight, so more gas in the atmosphere (pressure decreases the higher up you are, ex. pile a bunch of pillows, bottom pillow will feel most pressure) |
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Planet A and Planet B are the same size, but A has more gas in its atmosphere then B. All other things being equal, I would expect that |
The surface pressure of planet A is higher than the surface pressure of planet B |
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How can we determine the chemical composition of planetary atmospheres? |
1) Spectroscopy 2) Measure directly by probes (terrestrial planets) |
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Are the atmospheres of terrestrial planets similar or different? |
Wildly different ! |
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Comparisons between terrestrial planet atmospheres? 1) Moon & Mercury 2) Mars & Venus 3) Earth |
Moon (He, Na, Ar) & Mercury (He, Na, O) - thin (almost negligible) atmospheres (trillion times less pressure than Earth)
Mars & Venus (96% CO2; 4% N) - similar composition (very different pressures - mars minimal, Venus the most 90bars)
Earth (77% N, 20% O) - unique both in composition and pressure (1 bar) |
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Do properties of planetary atmospheres change over time? |
YES! -Fossil evidence that Earth's atmosphere has changed -Geological evidence that Mars atmosphere has changed (had higher surface pressure to allow for liquid water) |
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Temperature is average motion energy of particles. Where do particles near the surface get their energy from? |
-NOT internal heat (doesn't significantly contribute) -SUNLIGHT - the main source of energy for planetary surfaces (absorbed energy converted into motion energy) |
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Reflectivity of a planet depends on its... |
Surface composition and colour (darker surfaces absorb more light/reflects less) |
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The Moon and Earth are at the same distance from the Sun, but the Earth's reflectivity is higher...thus... |
The Moon's surface temperature should be higher than the Earth's surface temperature. |
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What is the "No greenhouse" temperature? |
What the surface temp would be in the absence of an atmosphere (using distance of planets from sun and their reflectivity) -if this were true, Venus would be colder than Earth...which is not true |
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The surface temperatures of Venus, Earth, and Mars are determined by what? |
Greenhouse effect (atmospheric blanket) -their atmospheres allow visible light in to heat the planetary surface, but make it more difficult for the infrared heat to escape the planet) -greenhouse gases absorb and reemit infrared radiation, thereby heating the lower atmosphere |
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Planets emit most of their radiation at... |
Infrared wavelengths (extremely hot objects emit visible and x-rays) |
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What are the 3 major greenhouse gases? |
1) H2O (water vapour) 2) CO2 3) CH4 (methane) |
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What is the process of volcanic outgassing? |
Process of releasing gases from the planet's interior and ejecting them into the atmosphere (dominant for of atmosphere GAINING gas)
Other minor sources: -Sublimation or evaporation -micrometeorites |
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What are the main gases released by volcanic eruptions? |
-H2O (only material brought to Earth by comets from Solar Nebula) -CO2 -N2 -H2S & SO2 (sulfur bearing gases)
-Since all terrestrial planets show previous evidence of volcanic activity, they must have gained their atmospheres by OUTGASSING, and so their early atmospheres should have contained the above materials |
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How are gases removed from the planet's atmosphere (atmospheric losses)? |
1) Recycling processes - gas removed from atmosphere but incorporated into surface (condensation or chemical reactions) 2) Permanent loss - thermal escape, impact blasts, solar wind stripping (is less significant for planets with strong magnetic fields to deflect solar wind) |
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How does the thermal escape process work (atmospheric losses)? |
-gas particles are removed permanently when they reach escape velocity (lighter particles reach EV faster & smaller planets have lower EV so particles escape easier) -larger planets can keep their heavier gases |
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The Moon & Mercury's atmosphere's presently? |
-only source of atmospheric gain is micrometeorites -extremely low density atmosphere (due to heavier atoms being retained for a while to form an exosphere) |
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Why does Mars have a lower pressure now than it did before? |
Small --> cooled faster --> less volcanic activity (less outgassing)
-Iron core solidified which weakened magnetic field --> allowed for Solar Wind to strip Mars' atmosphere (stripped of CO2) |
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How did Mars get its red colour? |
When mars cooled, iron core solidified, lost magnetic field, solar wind stripped CO2 and H2O dissociated to O and H by solar UV photons -O chemically reacted with iron in rocks and planet's surface to rust them and turn planet red |
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Will Mars every have liquid water again? |
No
Small size (cooled down faster), iron core solidified (magnetic field lost), solar wind stripped CO2 and H2O, less atmospheric pressure/less greenhouse effect, no liquid water |
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What is the surface of Venus currently like? |
-High density (90 bar) -Extremely hot (same temp day and night/at poles and equator) - because of strong greenhouse effect (there's 200,000 X's more CO2 than Earth) -100% cloudy cover -Hardly any winds/rain |
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Global Warming is thought to be caused by the... |
Addition of carbon dioxide |
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If Venus and Earth had similar compositions/size/outgassing...where has all of Earth's CO2 gone? |
It's in Earth's rocks! (carbonate rocks) |
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What are carbonate rocks? |
Ex. Limestone (contain carbonate ion CO3) |
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How do carbonates form? |
1) Ocean takes up CO2/dissolves it 2) Minerals and CO2 combine to form carbonates (by marine life/chemical reactions)
(Cycle - eventually volcanoes outgas CO2) |
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So why did Venus not form large quantities of carbonates? |
Formation of carbonates requires the presence of liquid water (since water comes from outgassing, why are there not comparabe amounts? --> Venus must have lost most of its water) |
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If the Earth and Venus had the same amount of outgassing (therefore should have had the same amount of water) where did all of Venus's Water go? |
Venus hardly rotates (therefore no strong magnetic field), solar wind stripped O and H atoms from UV photons |
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But why did all the water on Venus end up in the atmosphere in the first place? Why did Venus not just form oceans and keep them, just like Earth? |
Runaway Greenhouse Effect
-Venus is closer to the Sun, higher temperature, more evaporation (more water vapor in the atmosphere) --> water vapor is a greenhouse gas --> increasing temp (cycles) - it becomes so hot that CO2 is baked out of carbonate rocks |
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In a few billion years, the Sun will heat up the Earth much more than now; this will result in a Venus-type Earth? |
True (When the sun is ending its life, it will get larger and we will be closer to it) |
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Why did Earth retain most of its outgassed water? |
Cool enough for water to condense and form oceans -Magnetic field protects from magnetic field -Ozone layer protects from UV radiation |
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Why does Earth have so little CO2 in its atmosphere? |
Oceans allow CO2 to dissolve and form carbonates |
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Why is Earth's atmosphere primarily made of N and O? |
Outgassing primarily produces water, N2, and CO2
-Most of water in oceans, and most of CO2 in carbonates, N2 becomes dominant gas
-O2 is very reactive, so need continuous O2 suppliers (life - photosynthesis, buildup of O2 took 3 billion years) |
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Why does Earth have an ultraviolet-absorbing stratosphere? |
O2 is transformed to O3 in upper atmosphere by UV radiation (ozone is a good absorber of UV radiation)
- So need Oxygen for Ozone |
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Is it a coincidence that there is "just enough" CO2 in the atmosphere and not significantly more or less? |
NO, atmosphere will always adjust itself to have just the right amount of CO2 - CO2 Cycle
(When the sun was fainter we had more CO2, we have less CO2 now that the sun is warmer) |
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Describe the CO2 Cycle |
Warm Earth --> more evaporation/rainfall, CO2 dissolves to carbonates (greenhouse effect decreases)
Cool Earth --> less evaporation, outgassing CO2 builds (due to plate tectonics), planet warms again (greenhouse increases)
* process takes 10's of millions of years (plate tectonics drive this cycle/make the cycle so slow) |
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What was the Snowball Earth & Hothouse Earth? |
Evidence that temp dropped enough for oceans to freeze worldwide (ice reflects sunlight, so cooled down even further) -Since outgassing from volcanism would still produce CO2, and CO2 could not be converted to carbonates with no liquid water, increase atmospheric pressure, increase greenhouse effect, increase temp --> leads to "Hothouse Earth" |
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How do we look at short term changes in global temperatures? (recent climate change) |
Look at antarctic ice cores (Heavy water deuteriu when world is warmer, less when world is cooler)
- Can also analyze gas bubbles for CO2 levels in atmosphere (warm - high, cool - low) |
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Milankovitch Cycles and Temperature |
Milankovitch cycles (cycle of CO2 level fluctuations over years)
Changes in atmosphere is the main thing that determine the change in the climate (CO2 and temp have increased over time slowly) |
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What is currently going on with our climate? |
1) Earth is warming up faster and faster 2) Burning fossil fuels always produces CO2 3) Greenhouse gases will continue to heat up the Earth |
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What if we stopped burning fossil fuels immediately? (quit cold turkey) |
We've altered the Earth's climate for next few hundred years, regardless if we completely quit using fossil fuels |
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When will we see such effects as sea level rise? |
We can already measure that the sea level is rising (water expands a bit as it warms) -bigger problem when Greenland and Antarctica melt (less so for north polar ice) |
