Transcript Michigan`s Glacial History ppt

Michigan’s Glacial
History
How do scientists prove that
glaciers once covered
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 cooled…
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 warm,
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 warm,
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 warm,
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 warm,
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 sediments
Moraines are made of unsorted
sediments. Only mass movements
and glaciers deposit unsorted
sediments.
Mass Movements?
Glaciers??
Moraine Deposits have the same shape as the
Great Lakes.
• Michigan
moraines run
parallel to the
shoreline.
• So how do
they relate??
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
11.15 Identify glacial features
using a Topographic Map
• Glacial topo map lab: