The Ancient Shore of Lake Algonquin EarthCache
Hidden : 4/2/2008
Difficulty:
1.5 out of 5
Terrain:
1 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

You are standing on the shore of Lake Algonquin. Well, you are standing where it used to be.

Until this area was incorporated as the City of Evanston in 1863 it was known as Ridgeville. Ridgeville was named after the most prominent local geographic feature, a long ridge running along the lakeshore. Ridge Avenue now runs along the length of this ancient line. But when and how did the ridge originate?

The simple answer is that it is a moraine that formed during the Ice Age. At the end of the Pleistocene Era the Laurentide ice sheet made a series of advances across the Midwestern landscape. At its southern limit it reached as far as the Ohio River, scouring the land flat throughout Illinois. During the last advance, which peaked around 18,000 years ago, the Wisconsin Glacier advanced through the bed of what is now Lake Michigan, deepening the gouge in the terrain created by earlier advances. Debris scraped up by the glacier was left in a pile along its edge. As the ice retreated the debris was left behind, resulting in the ridge you see today.

This ridge became the shore of Lake Algonquin. As the Wisconsin Glacier retreated around 11,000 years ago the melting ice pooled in the proglacial lakes left behind. Lake Algonquin was formed of much of present day Lakes Michigan and Huron. The moraine on which you are standing formed the rim of the bowl that kept the water in place. Eventually, as the glacier retreated further around 9,500 years ago, an outlet was exposed that allowed the water to drain east to the Atlantic Ocean. The water level dropped as the water flowed out and Lake Algonquin was gone. Eventually the water returned but the level was not as high as it had been. Lake Michigan and Lake Huron still share the same water level, but they are pinched apart by the Straits of Mackinac. While they are still effectively linked they are know known as individual Great Lakes instead of as the even larger one from the past, Lake Algonquin.

Lake Algonquin was once held in by this ridge. Lake Michigan has its own shore. How much has the water dropped? How far did the shoreline move? That is for you to determine. This may not be the most picturesque location for an Earthcache, but man takes less time to develop an area than nature. Try to imagine the area as it must have appeared 10,000 years ago.

To claim credit for this earthcache you must:
• Estimate the distance the shoreline has moved. Estimate the drop in water level in feet from the line of the ridge to the current level of the lake. Send this information in an email to the cache owner, do not post in your log.
• Take a picture at or near the posted coordinates. Your picture must show the slope of the ridge and include your GPS unit.

Logs without the required email or photographic evidence will be deleted.

Additional Hints (No hints available.)



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