ESC Pleistocene Glaciation Chapter
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- Louis Agassiz
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-19th century Swiss geologist
-Suggested that eupope and north america were covered by thick ice sheets in the recent geologic past. - Evidence for past continental scale ice sheets
- Erratic boulders, Ground moraine found in northern parts of US and Europe, Glacial straiations on rocks, layers of till.
- Erratic boulders
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-large boulders transported by glacial ice.
-can be traced back to their source rock bodies, marking flow direction of ice sheets. - Milutin Milankovitch
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-1930's
-calculated the amount of sunlight each latitude received in every phase of earth's orbital variations.
-Pacemaker of the Ice ages - Milankovitch Theory
- Ice ages occur when orbital variations cause the northern hemisphere to receive less sunshine in the summer. Predicted that ice ages would peak every 100,000 and 41000 years.
- Axial tilt affect on solar radiation
- When the tilt is decreased, polar regions receive less sunlight; when it is increased, polar regions receive more sunlight.
- Positive feedback factors
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-A changing albedo- increased snow on land
-Less evaporation-sea is less salty
-Biological processes that change CO2 concentration. - Pleistocene interglacials typically lasted how long?
- 10,000 years
- The precent interglacial began how many years ago?
- 13,000
- Little Ice Age
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-1300'2-mid 1800's
-Montain glaciers advanced significantly.