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A continental glacier is an ice sheet that covers large portions
of land and is caused during extended periods of cold temperatures
called ice ages. Ice ages can last for thousands to tens of
thousands of years. As glaciers move slowly southward, they pick up
eroded material and carry it as part of the front of the glacier
and as the bed load. This material is called glacial till.
Till is deposited in several places on and along a glacier.
These piles are called moraines. Moraines formed where two glaciers
meet is called a medial moraine. Moraines on the side of a glacier
is a lateral moraine. Till piled at the front edge of a glacier is
called a terminal moraine. Moraines are composed of sand, gravel
and pebbles. Large boulders mixed among the till are called
erratics.
As a glacier melts, the area in front of a terminal moraine is
called the outwash plain. Massive amounts of water wash away loose
sediments making a nearly flat area in front of a steep ridge of
deposited till. Outwash plains can extend for miles before relief
topography starts to take shape.
The last ice age to cover North America ended nearly 15,000
years ago. At that time the Michigan Lobe extended south over what
we today call Lake Michigan and advanced into Northeast IL and
Northwest IN. This last advance brought eroded material from
northern latitudes of Canada, Minnesota, Wisconsin and Michigan and
deposited them in a ridge extending from Porter and Lake County in
Indiana and westward through Kankakee County IL. This terminal
moraine is called the Valparaiso Moraine.
As the Michigan Lobe melted over a 8000 year time period, water
continued to erode and flatten the outwash plain in front of the
Valparaiso Moraine. This area is called the Kankakee Outwash Plain
and serves as the major river basin for the Kankakee River.
At the posted coordinates (N 41° 15.119 W 087° 28.079), you are
very close to the front edge of the Valparaiso Moraine. Take an
elevation at these coordinates. The moraine continues south along
HWY 41 and reaches an additional 7 feet at the leading edge.
Go south along HWY 41 to coordinates N 41° 14.431 W 087° 28.062
and park along the shoulder. Take an elevation reading. Looking
back north, you can see the front edge of the Valparaiso Moraine.
As you look at the Looking south, the vast flat area in front of
you is the Kankakee Outwash Plain.
To log this cache email the following information
1) The elevation at the posted coordinates
2) The elevation at the leading edge of the Valparaiso
Moraine.
3) The elevation at the Kankakee Outwash Plain
4) Calculate the thickness of the Valparaiso Moraine at the leading
edge.
5) To the northwest of your location at the Kankakee Outwash Plain,
you will see an excavation. Do you see any eratics or is it mostly
sand and pebbles?
6) Post a picture of your GPS unit with the Valparaiso Moraine in
the background (you included is a BONUS!)
Congrats to TankHounds and Shydog on the FTF