Ice_Ages_lecture - At its maximum about 20 thousand years ago an ice sheet covered most of Canada and part of the northernmost U S Today in the

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At its maximum about 20 thousand years ago, an ice sheet covered most of Canada and part of the northernmost U. S. Today in the Northern Hemisphere an extensive ice sheet covers only Greenland.
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A few thousand years ago, rock debris embedded in an ice sheet had cut parallel grooves and had polished the surface of this outcrop in southern Ontario. Angular, unsorted fragments within the bedrock, also of glacial origin, were deposited by an ice sheet 2.4 billion years ago.
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Today we live in an “Icehouse” Earth, with major ice sheets in the polar regions (Greenland, Antarctica). At least one earlier Icehouse Earth episode has been identified.
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“Greenhouse Earth” is a time when there is no glaciation anywhere, and this has been the standard climatic state. The Mesozoic Era, the Age of Dinosaurs, was a time of Greenhouse Earth.
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“Snowball Earth” is a far more severe climatic state in which the entire planet is frozen solid. The ocean was covered by ice estimated to have been as much as a kilometer thick. Climate was extremely cold and dry.
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The opposite of Snowball Earth is “Hothouse Earth,” a time of intensely hot climate worldwide. Hothouse Earth followed immediately upon the heels of Snowball Earth. You would not want to be around during either Snowball or Hothouse Earth!
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years, polar glaciation is nicely explained by continental drift: where the landmasses are located with respect to Poles and the Equator. During the Paleozoic Era a supercontinent
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This note was uploaded on 09/14/2009 for the course GEO 401 taught by Professor Lassiter during the Spring '08 term at University of Texas at Austin.

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Ice_Ages_lecture - At its maximum about 20 thousand years ago an ice sheet covered most of Canada and part of the northernmost U S Today in the

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