EAES 101 Lecture 25: Historic Climate Change
8 Nov 2016
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11/7/16: varied considerably, fluctuating between periods of both warmer and colder than current temperatures. Sediments deposited directly by glaciers as they melt are characterized by: an absence of sorting. Glacial till: debris deposited after ice melts, characteristically, poorly sorted, angular, contains material not native to the region. Evidence of past glaciation: tillite: glaciers grind up surface rocks-debris becomes lithified, moraines, straiations, dropstones, loess, eratics, u-shaped valleys-harder to see in the rock record. Iclicker: you"ve taken a 100 m core of ocean sediments and found dropstones all the way through them, from top to bottom. What does this tell you about the history of glaciation in the area: there was constant glaciation for the whole period represented by the sediments. Iclicker: you have now drilled a core of sediment from the ocean near the equator. You find 100 m of sediment that has thin layers of dropstones every 10-20 m or so.
