Glaciers Earth Science Chapter 6 p 154 159 168 173 Valley and Piedmont Glaciers Southern Hemisphere Malaspina Glacier Alaska Northern Hemisphere Glacier movement tracked by stakes Glacial Snow Budget Iceberg Photo Crevasse Striations and polish 1 Cycle of valley glacier erosion U Shaped Valley with tarns Hanging Valley Arete Cirque Horn Fiord http jesse usra edu articles iceagemodule iceagemodule paper html Lateral moraine Lateral and Medial Moraine Moraine deposit 2 http ns geo edu ro paleomag Loess Continental Glacial deposits Pleistocene Ice Maximum Bering land bridge Upper Midwest End Moraines Coastal moraines of New England http www atmos washington edu dennis Our Changing Climate html Upper Midwest drainage before glaciation Upper Midwest Drainage after glaciation Pluvial Lakes of Southwest Deranged drainage after ice melts 3 Ice Age Sea Level on North America Past Glacial Ages Location of 300 MY Continental Glaciation Pliocene Pleistocene Ice in Antarctica starting about 40 m y a Widespread N Hemisphere ice about 3 mya Advances every 40 000 to 100 000 years Karoo Ice Ages 260 to 350 mya Lasted 90 million years Wegener s evidence of continental movement Location of 300 MY Continental Glaciation with continents located 300 mya Past Glacial Ages Documentation Andean Saharan Ice Ages 430 to 460 mya Lasted 30 million years Cryogenian 630 to 850 mya Lasted 200 million years Periods of all Earth covered with glacier Drift Loess and marine deposits Oxygen isotope ratio in shells Air trapped in ice CO2 levels Huronian Over 2 billion years ago Lasted 300 to 400 million years Causes Elliptical orbit Axial Tilt variation Land mass configuration High latitude land mass Antarctica High elevation in westerlies Andes Cascades Coincidence of astronomical variations of Earth in relation to Sun Orbit shape eccentricity Axial tilt amount obliquity Tilt direction superimposed on orbit shape progression of the equinox CO2 levels may be effect and not cause 4 obliquity Precession of axial tilt Milankovitch cycles Northern hemisphere insolation differences due to Milankovitch cycles Oxygen isotope fractionation Temperature record from O 18 Threshold diagram Positive Climate Feedback Loops Ice albedo feedback loop Ice albedo decreases temperature increases ice Reduced ice increases temperature 5 Positive Climate Feedback Loops Ice albedo decreases temperature increases ice Reduced ice increases temperature Glacial periods result in larger arid areas increasing delivery of iron nutrients to sea lowering CO2 levels and temperature Lowering sea level will expose reefs to weathering Reaction consumes CO2 lowering temperature Rising sea level has opposite effect Temperature compared to sulfur aerosol concentration Negative Climate Feedback Loop Forest cover negative feedback Forest die out during glacial ages reducing mechanism to remove CO2 from atmosphere increasing temperature Nutrient cycle Nutrients related to sea level change Ice Age Sea Level on North America 6
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