The landscapes of Northern America,
especially around the five Great Lakes, was formed during the Wisconsin
glaciation. The Crown Point phase of this glaciation occurred over a 2,400 year
period, beginning around 15,200 years ago.
At this time, the part of the glacier that would become Lake Michigan
was so thin that it was held back by the topography of the land and was
restrained only to a certain area (Schoon, p. 20). Large amounts of sediment piled up around its
edges. This long, curving ridge of sand
is known as the Valparaiso Moraine and is covered by glacial till. After it was formed, the Lake Michigan part
of the glacier retreated and then advanced again and the Tinley/ Lake Border Moraine
was built. This moraine is narrower and
not as high as the Valparaiso Moraine (Schoon, p. 21). These two moraines are important because they
form part of the Eastern Continental Divide (Schoon, p. 22).
Lake Michigan (http://en.wikipedia.org/wiki/Lake_Michigan)
Kettle Lakes are large holes form
when enormous chunks of ice break away from a glacier and are buried by
sediment deposited by water from the melting glacier (this is called outwash). When the ice thaws, the sediment collapses,
forming a large hole. The hole is then
filled with water and becomes a kettle lake. Cedar Lake is the largest natural lake in
northwest Indiana and seems to be a kettle lake. Sediments are often washed into kettle lakes,
making them shrink in size (Schoon, p. 23).
Cedar Lake (http://en.wikipedia.org/wiki/Cedar_Lake,_Indiana)
To the south of the Valparaiso
Moraine lies the Kankakee Outwash Plain.
This was created by meltwaters which were carried away from the glacier
and eroded valleys through the moraine.
When the water moved past the moraine and the ground leveled out, the
water lost speed. It deposited sand,
forming a flat plain. Although Lake
Michigan is known for its dunes, there are actually more dunes in the Kankakee
Outwash Plain than along Lake Michigan (Schoon, p. 24).
Groundwater is an essential natural
resource. Areas with glacial outwash
have a good supply of groundwater. Areas
without much glacial outwash have little groundwater because hard rocks are not
comprised of much open pore space for holding water. That water also smells and tastes bad because
of the dissolved mineral matter it often contains. Groundwater is necessary as it is our principal
source of drinking water (Camp and Richardson, p. 12).
The Ohio River most likely existed
before the Pleistocene ice ages.
However, it was much shorter back then.
Glaciers shed meltwater into the Ohio River. When glaciers retreated, sediment filled the
valleys, creating a higher floodplain.
Rivers eroded this area, creating the channel that is now there (Camp
and Richardson, p. 12)
Three major river valleys in Indiana
have been affected by glaciers. The
largest of these is the Wabash River. It
was formed by meltwater floods from the Wisconsinan ice (Camp and Richardson,
p. 218). The Marion- Mahomet Valley is
filled with outwash. The sediments
deposited in this valley are porous and therefore able to hold a large amount
of groundwater. This valley existed before the glaciers, but
was made larger by the floods that came after several glacial advances (Camp
and Richardson, p. 219). The Teays River
in Ohio and West Virginia was once thought to have cut through Indiana, but recent
research proves otherwise. Instead, the
Teays River appears to have joined with the Kentucky and Licking Rivers. More research is needed to know the exact history
of this river (Camp and Richardson, p. 221).
Wabash River Valley (http://en.wikipedia.org/wiki/Wabash_River)
Sources
Camp, Mark J., and Graham T. Richardson. Roadside geology
of Indiana. Missoula, Mt.: Mountain Press, 1999. Print.
Schoon, Kenneth J.. Calumet beginnings: ancient
shorelines and settlements at the south end of Lake Michigan. Bloomington:
Indiana University Press, 2003. Print.
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