ATOC notes March 30

ATOC notes March 30 - Moraines in US-Wisconsin same time...

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ATOC notes March 30, 2009 GLACIAL CYCLES What is a Glacier? : Slow moving river of ice - Typically in canyons Difference from Ice sheet? - Earth: presently colder than in the past - Recall general decline in CO2 concentration over last billion years - Not much glaciations in the past - 2 or 3 possible exceptions (“snoball earth”) Geological evidence for glaciations - Moraine - Geological feature caused by glaciers - Glaciers scoop out large deep valleys - Material pushed around by movement of glaciers - Glat bottom gulleys Stratigraphy - Matching geo sediments by age - Units of sed. Often given names (either by discoverer or by their location)
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Unformatted text preview: Moraines in US-Wisconsin same time Wurn-Illinoian same time Riss-Kansan same time Mindel-Nebraskan same time Gutz in order from youngest to oldest Oxygen isotopes-Normal oxygen has 8 neutrons and 8 protons, molecular weight of 16-Small fraction of O2 has 2 extra neutrons thus is oxygen 18-So in water we can hve this normal H20 or heavy water H218O-Harder to evaporate heavy isotopes, so left behind-Easier to precipitate heavy isotopes, vapor is lighter again...
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