michigan’s glacial history

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