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Geology test 2 umw
almost finished!
| Question | Answer |
|---|---|
| Bathymetry | topography |
| Seafloor topography | mid-ocean ridges, trenches, shelves, abyssal plains, passive vs. active continental margins |
| Abyssal plains | deepest part of seafloor except for trenches |
| Salinity | concentration of dissolved salts |
| Highest salinity of salt water | center of oceans near equator (warmer, less fresh water) |
| Greatest evaporation | inland seas |
| Average salt water temp. | 17 deg. Celsius |
| Causes of surface currents | wind currents drag water molecules, Coriolis effect |
| Coriolis effect | developed by a French engineer in 1830s, the effect of Earth’s spin on currents |
| North flowing surface currents | in Northern hemisphere, deflected east of wind currents, clockwise cells |
| South flowing surface currents | in southern hemisphere, deflected West of wind currents and counter-clockwise cells |
| Causes of deep ocean currents | surface currents, coriolis effect (causes upwelling near equator), changes in temp, salinity and density |
| Deep ocean currents | go down at the poles and up at the equator, creates a conveyer belt that circulates throughout the globe |
| Causes of tides | gravity, centrifugal force, Earth tilts w/ respect to moon, sun’s gravitational pull, geometry of coastlines vary, air pressure |
| Gravity on tides | pull of the moon causes seawater to bulge on side of Earth closest to moon |
| centrifugal force | from Earth’s revolution around the center of mass of Earth |
| Tidal reach | maximum change in sea level in a given area ex. Bay of Fundy, Canada (up to 60 ft daily) |
| Intertidal zone | area flooded at high tide and exposed at low tide (tidal flat) |
| Causes of sea-level change on a global scale | mid-ocean ridge spreading (more rifting and spreading displaces more water onto land), ice sheets melting |
| Sea level 18,000 yrs ago | coast line was farther out, since sea level was lower, more land bridges |
| Glacier | a layer of ice that persists year round and flows under gravity |
| Louis Agassiz | (1807-1873) Swiss paleontologist, geomorphologist, immigrated to US in 1846, founded Natural History museum at Harvard |
| Agassiz contributions | worked with Georges Cuvier on fossil fish, supported catastrophism and fixity of species, 1837 proposed a recent great ice age accepted by 1850s, proposed global ice age (discredited) |
| Field evidence of ice sheets | glacial erratic and till |
| Glacial erratic | large boulder that is out of place and source is miles away, carried by a glacier, Geology is different from that area, ex. Central Park, NY |
| Till | unsorted, angular debris left by melting ice |
| Last ice age | ended 11,000 yrs ago and covered 30% of Earth |
| Mineral | solid naturally occurring, inorganic, crystalline structure (ice is a mineral, glacier is a metamorphic rock) |
| Nature of ice | high reflectivity, if high % of global ice then more reflectivity and cooling, ice less dense than water, water expands when it freezes |
| Types of glaciers | Alpine glaciers and continental glaciers |
| Alpine glaciers | high elevation, ex. Greenland mtn cap, Alaskan Valley glacier |
| Continental | “ice sheets”, Greenland and Antartica, depresses land down and causes subsidence |
| How glaciers form | climate (low temp, high precipitation) and topography (smaller angle of repose to permit build-up of ice/snow |
| Change from snow to ice | takes decades to millennia |
| How glaciers flow | basalt sliding in temperate regions (bedrock creates thin layer of water for ice to slide on) and internal flow in polar regions (land frozen) |
| Brittle behavior | occurs 200 ft down in ice |
| What are the fastest glaciers? | Alpine on average 25-1000 ft/yr |
| Zone of accumulation | in center, where snow and ice build-up |
| Zone of ablation | at the margins of glacier |
| Toe | end of glacier, where calving (breaking off of ice) occurs |
| Advance | more in zone of accumulation and thus the toe moves forward and the glacier is larger |
| Retreat | more zone of ablation, so higher equilibrium line, toe moves up slope and glacier is smaller |
| When glaciers reach the ocean | floating glacier not on the land that will eventually clave ex. Larson Ice shelf (2002) |
| Drop stone | a glacial erratic on the sea floor |
| How Earth’s atmosphere formed | process called outgassing, which outgassed mostly water and carbon dioxide (NOT oxygen) |
| Atmosphere composition | 20% oxygen, 79% nitrogen (can’t go into rocks and minerals), 1% other |
| Where has the water gone? | water condenses to form the oceans, evidence from stromatolites at least 3.5 byo, pillow basalts at least 3.8 byo |
| Where has carbon dioxide gone? | absorbed into limestone and other carbonates (requires lots of water), and photosynthesis |
| Carbon cycle | involves limestone, oceans, and oil/coal |
| How we got so much oxygen | dissociation of water (very slow), aerobic photosynthesis |
| Oxygen levels | 1% by Archean (prokaryotic), 10% by Proterozoic (eukaryotic & multi-celled), 20% by Paleozoic (abundant mutli-celled life) |
| What protects Earth’s atmosphere? | ozone at high levels of atmosphere and Earth’s magnetic field |
| Greenhouse gases | CO2 (biggest concern since long life span), NO2, CFCs, methane, ozone |
| Greenhouse effect | UV radiation comes down on earth, 50% is absorbed, the rest is reflected back as longer wave infrared radiation and trapped by Greenhouse gases |
| Keeling curve | Hawaiian data set since the 1950s of the monthly mean of carbon dioxide, has been exponential since 1700 |
| Maximum carbon dioxide each year | during the spring/summer months in the northern hemisphere |
| Aerosols | tiny particles, lead to acid rain and ozone depletion ex. Waterdrops, acid drops, pollen, volcanic ash, CFCs, carbon soot |
| Acid rain | comes from sulfur-rich coal |
| Ozone depletion | stem from CFC use, migrate to upper stratosphere, Montreal Protocol, replaced by HFCs, has been depleting 4%/yr since mid 1970s, only over Antarctica |
| CFCs(chloroflurocarbons) | used in aerosol sprays, refrigerants, Styrofoam, plastics, long-lived (100 yrs), |
| Weather | atmosphere conditions for short time frame |
| Climate | longterm patterns and changes over time for a region or glob (temp & precip) |
| What controls climate | latitude (determines amount of solar energy), altitude, oceans (coastal regions have less variation in weather), topography, Coriollis effect (winds deflected by Earth’s spin |
| Sea ice | frozen seawater (not grounded) |
| Evidence of glaciation in bedrock | glacial polish and striations (scratches) |
| Evidence of glaciation- Erosional landforms | Alpine has a U-shaped valley and hanging valley (vs. v-shaped and trunk in river) |
| Evidence of glaciation- depositional landforms | moraines, glacial deposit of debris as they melt creating a hill |
| End moraine | toe of the glacier, show the furthest glacier reached, ex. Bylot Island, Canada |
| Evidence of glaciation- glacial deposits | till, erratics, dropstones, glacial outwash, glacial varves (lake sediments), Loess (windblown clay) |
| Continental scale glaciation controls | isostasy (ex. US and Canada), drainage of N. American rivers |
| Pleistocene Epoch | 1.8 mya to 11,000 years |
| Regions of present day glaciation | Greenland and Antarctica |
| Ice sheet land data | till (moraines), landforms, striations, glacial polish, erratics/dropstones, pollen, Paleosols (warmer interglacials=soils) |
| Marine evidence | timing of period can be found by comparing isotopes of oxygen and hydrogen in seafloor sediment (water is heavier when ice is formed and so is sediment), in interglacial it remains unchanged |
| Foraminifera | single-cell eukaryote, whose shells are “heavy” with oxygen18 |
| Which is more detailed land or marine record? | marine over 20 events in last 2 mya while land is only 4 |
| Climate effects from Ice Ages | tundra shifted South, greater rains in north America (less in tropics), windy=Loess deposits |
| Ice shelves | floating glacier |
| Long-term causes of ice ages | plate tectonics and Low amounts of CO2 |
| How plate tectonics affects ice ages | land masses at high latitudes, land masses above sea level, restricted ocean currents |
| How low amounts of CO2 affects ice ages | increase in marine organisms, increase in swamps (photosynthesis), reduces volcanism |
| Pleistocene plate tectonics 1 | about 50 mya, India converged on Asia causing Himalayas to uplift and plateau enhanced |
| Pleistocene plate tectonics 2 | Australia and S. America fully separate from Antarctica, cold currents around Antarctica |
| Pleistocene plate tectonics 3 | Panama land bridge closed opening between Americas, gulf stream permits more snow in arctic region, ice sheets now in Arctic |
| Short-term causes of ice ages | Milankovitch cycles-1920s, Eccentricity (100k yr cycle), Tilt (41k yr cycles), wobble(23k yr cycle) |
| Wobble | timing of seasons and Earth’s orbital position around sun |
| Eccentricity | Earth’s pathway around the sun |
| Combined effects of the cycles | contribute to the amount of insolation |
| Timing between glacial advances | 20, 40, or 100 thousand years |
| Glaciations require | cool summers |
| How much climate change do Milankovitch cycles account for? | 4 deg Celsius decrease, but there has been a 5-7deg decrease on coasts and 10-13 deg decrease on land |
| Feedback mechanisms | (contribute to cooling) reflectivity (more clouds, more ice) |
| If Total melting of ice sheets | 230 feet rise in sea level |
| In the last 150 yrs | warming, fewer icebergs, retreat of ice sheets |
| How long have we had an interglacial period? | 11,000 yrs, usually last only 10,000 |
Created by:
lfalkens
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