EAS

EAS 100 Continental crust – less dense rock with more silicon, aluminmum Oceanic crust – more dense rock with more iron, magnesium Single supercontinent – Pangaea Three plate boundaries: Spreading centers – new crust gets created Subduction - one crust goes under another crust Transform faults – two plates grinding in parallel with each other Earthquakes: Focus – point where energy is first released during an earthquake Epicentre – the point on earth surface that is directly vertical above an earthquake P waves – primary waves, pass through solid/liquid/gas. Refracted by earth core S waves – secondary waves, pass through solids only. Blocked by earth core Benioff zone – the submerged area of a crust that has been in subduction Water: Sea level rising Oceans 97.5%, ice sheets 1.85%, groundwater, .64%, lake/river/atmosphere .01% 97% is ocean, 2.5% freshwater, .4% of fresh water is renewable Hydrologic pathways – evaporation and transportation, condensation/precipitation, surface runoff and infiltration and subsurface flow Actual renewable water = internal water sources + inflow of water – outflow of water Blue water resources – waters in river, aquifers, lakes, wetlands, impoundments (dams) Green water resources – soil in unsaturated zone Green water flow – from crops, forests, grasslands and savannas Factors that influence stream behavior: width/depth of channel, channel gradient, average velocity and discharge Confining layers – regions of low conductivity are made up of fine-grained particles with a large percentage of mesopores and micropores that restrict the rate of water movement Aquifier – geological unit that can store enough water and transmit it at a rate fast enough to be hydrologically significant An unconfined aquifer – aquifer whos upper boundary is the water table, the water table is defined as the path at which water pressure equals atmospheric pressure Recharge – area is defined as a portion of drainage basin where ground water flow is directed away from the water table Hydraulic head or piezometric – specific measurement of liquid pressure above Ice: Elevation of snow lines lower in polar areas and lower in coastal areas Glaciers – fuck ton of snow accumulates to form glaciers, above snowline 6 Types) Cirque – concave basins carved by the base of a glacier Valley – streams of flowing ice that are confined within steep valley walls Fjord – Next to the sea, often turn into icebergs Icecap – covers mountains and flow radially Icesheet – accumulation of snow over time becomes frozen mass that is an ice sheet, greenland/anarrctica include 95% of earths glaciers Ice shelf – not as thick as icesheet but still occupy parts of anarctica Ice ages – last one 10ka ago, many glacial/interglacial peroids in last 2Ma Glacier ice – forms by evaporation of points on snowflake, just one one block which is all ice Glacier ice is finely layered, clean ice layers represent winter snow, dust laywers represent relatively dry summer, ice also traps atmospheric gases, pollen etc, ice cores provide valuable environment records Flow of ice – fastest in the center, slowest at thee edges, total movement = internal flow + slide on base, polar glaciers are frozen onto bedrock, don’t slide Brittle upper layer – top 50m of a glacier is brittle, it doesn’t flow Polar glacier – below freezing point, cliff terminus and ice is ablated by falling front of glacier Temperate glacer – close to freezing point, has liquid base (round terminus, ice is ablated from top and bottom) Accumulation – snow added Ablation – loss of ice/snow (melting, evaporation, calving) Balance = accumulation – ablation (negative balance receding) Accumulation exceed ablation in upper part of glacier Abalation exceed accumulation in lower part Flow is relatively upward, toward surface Accumulation/ablation zone are separated by equilibrium line, we can see it in the summer through dirty vs clean zone, icefloe is parallel to surface Glacier surge – move several km per year, related to buildup of water at base Rapid glacier retreat – occurs in fjord when it retreats from a sea-floor shoal Erosion: Striations – a line that is grinded? chatter marks – little holes Erosion features landform: U-shapped valleys, circques (bowl shaped valley), hanging valley, aretes (sharp edge ridges), horns (pointed pyramidal peaks) Glacial deposits: till- poorly sorted sediment Terminal/lateral moraines – accumulation oft ill are morains, form at the terminus of a glacier, lateral morains at edges Medial morains – where two glaciers join Drumlins – ice sheet mould oval hills Eskers – temperate glacier are very wet, rivers flowing beneat ice leave ridgers of well sorted sand and gravel which are called eskers Kames – piles of sand and gravel accumulated in streams and lakes on top of ice Sea ice – air temperature falls below zero, freezes together to make continuous ice cover, upward movement of ice (45cm/yr) Movements of sea ice – sea ice move several km/yr, ice crack producing open water, coverage of ice mases produces pressure ridges, large openings in sea ice are polynyas As sea ice freezes salt will flow down and circulate in deep ocean bases (sea ice very reflective high albedo, reflects light/heat and contributes to coldness of arctic regions). Permafrost – frozen ground, contains ice that froze during glacial ages, below is geothermal energy raises temp, thickest in areas that were not covered by insulating ice sheets Climate: 5 variables) Temp – max min average Precipitation – rainfall amounts snowfall amount Humidity Wind – average, peak, direction Cloud cover Overall warming trend of past 150years, fluctuates between decades. Glacial ice records – place markers indicating the year, we see glacial retreat Historical proxy records – frequency of dust storms, freezing date of lake etc Biological climate proxies – tree-ring width show correlation to climate, wider means warmer temperature Isotopic climate proxies – oxygen isotopes occur in water. As ice sheets grow O18 increases in water, decreases in continental icesheet Quaternary glaciation – last 2 million years, cold climates world-wide, glaciers deposted stuff in places where there are no longer glaciers, Europe had 4 advances/retreats Sea level change – in areas that were glaciated raised beaches signify fall of sea-level relative to land, due to isostatic rebound of lithosphere following remove of ice load Many icebergs were created through 6 layers of ice-rated debris Pollen records – provides sample of land vegetation that is easily preserved Isotopic record – water evaporates, vapour contains LESS O18, icesheet grows O18 increases in water and decreases in ice sheets. Last glacation started 70k years ago and ended 10k years ago, we are expected for another ice age in 10k years