Michigan’s Glacial History. How do scientists prove that glaciers once covered Michigan?
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Transcript of Michigan’s Glacial History. How do scientists prove that glaciers once covered Michigan?
Michigan’s Glacial Michigan’s Glacial HistoryHistory
How do scientists How do scientists proveprove that that glaciers once covered glaciers once covered
Michigan?Michigan?
Each of the Great Lakes began as a river.
Image from Earth Science, Tarbuck and Lutgens, 2003
Theoretical Michigan Before the Ice Age
When the climate When the climate cooledcooled……
Ice advanced southward from Canada over the
Great Lakes Region.
As the climate cooled…
• The rivers froze.
• Glaciers moved through them – widening and deepening them to form today’s lake bottoms.
14,500 & 14,000
13,000
11,000 damned to the North
9,500 two outlets
When the climate began to When the climate began to warmwarm, , glaciers began to retreat.glaciers began to retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
When the climate began to When the climate began to warmwarm, , glaciers began to retreat.glaciers began to retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
When the climate began to When the climate began to warmwarm, , glaciers began to retreat.glaciers began to retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
When the climate began to When the climate began to warmwarm, , glaciers began to retreat.glaciers began to retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
http://www.ofps.ucar.edu/gapp/networks/images/greatlakes_map.jpg
Kettle Lakes
S.E. Michigan Kettle Lakes
Moraine Deposits = unsorted sedimentsMoraine Deposits = unsorted sedimentsMoraines are made of unsorted
sediments. Only mass movements and glaciers deposit unsorted
sediments.
Mass Movements?Mass Movements?
Glaciers??Glaciers??
Moraine Deposits have the same shape as the Moraine Deposits have the same shape as the Great Lakes.Great Lakes.
• Michigan moraines run parallel to the shoreline.
• So how do they relate??
Other glacial evidence…Other glacial evidence…
Kalkaska, Michigan
Why do scientists believe that glaciers once covered Michigan?
• Michigan is covered with unsorted moraine deposits.
• The moraine deposits follow the outline of Great Lakes.
• Other depositional features such as drumlins and kettle lakes are found throughout Michigan.
• Erosional features like striations are found in Michigan as well.
11.14 Explain what happens to Earth’s crust when a glacier is
removed.
• Isostatic Rebound– The upward movement of the Earth’s crust
• Glacial topo map lab:
11.15 Identify glacial features using a Topographic Map
