eesci final 3

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eesci final 3
2011-05-11 13:47:48

esci, glaciation
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  1. Pleistocene glaciations
    -most recent ice ages
  2. glaciers
    -persistant mass of ice that forms on land and flows like water (ductile deformation at depth-brittle fracturing near surface) down slope under the influence of gravity
  3. Geological evidence of glaciation
    • terrestrial - erosion (horns cirques and u shaped valleys) glacial striations-scratches in bedrock
    • depositional environments- ground moraine under ice
    • moraine ridge- at the edge of glacier
    • outwash plain - sediments worked by streams
    • eratics - boulders in the middle of nowhere
  4. Marine evidence of glaciation
    • O18 and O16 ratios measured in fossil foraminifera
    • Core evidence - annual bands of ice give a climate record, ox. isotopes can give you temp.
  5. Effects of Glaciation
    • Isostatic effects- vertical movement of lithosphere & asthenosphere (uplift)
    • Drainage effects - creation of Great Lakes, great basin -fluvial lakes and ice dams
    • Sea level falls when glaciers form, rises when they melt
  6. Pleistocene extinction theories
    • extinction of large mammale in North America
    • climate change-( but extinction did not happen all at once worldwide)
    • Overhunting - a small population of large mammals (inverse correlation with body size) worldwide timing matched human development
  7. Causes of Pleistocene glaciations