Friday, August 1, 2014

Hitting the trail at High Cliff as August arrives

The ledge along the eastern shore of Lake Winnebago is is part of a ridge of rock that forms the "backbone" of the North American continent.  It stretches nearly 1,000 miles in an arc across the Great Lakes from western New York into southern Ontario in Canada woth through the Upper Peninsula of Michigan into Wisconsin.    It is known as the Niagara Escarpment because Niagara Falls cascade over it's edge.
What is now the escarpment was once soft mud on the floor of shallow seas that covered most of Noth America over 400 million years ago. At one time, Wisconsin had a tropical climate, being located about 20 degrees south of the equator, prior to plate tectonic movement northward.  The escarpment is a steep cliff face at the edge of a cuesta, a sloping ridge made of slightly tilted layers of rock.  The cliff formed when soft, crumbly Ordovician shale eroded away beneath harder, Silurina dolomite, (a Magnesium rich limestone), which then broke creating a  flat, cliff face.  The Niagara Escarpment was formed by movements in the earth's crust causing rocks to sag into a depression where Michigan is now.  The up-tilted, exposed edge of this bowl formed the Niagara Escarpment, which faces west in Wisconsin and north in New York.
During the last ice age, the rock ridge caused a vast glacier moving south from Canada to split into two lobes forming GreenBay and Lake Michigan.  About 10,000 years ago, water from the melting glacier found it's way into fractures into the ledge, enlarging them to creating caverns, including Ledge View.  Springs flow from the escarpment, recharging groundwater.
About 1,000 years ago, Native American built earthen effigy mound in geometric and animal shapes to hold burials and mark clan territories and ceremonial sites.  European settleres built kilns to burn dolomite to make lime used for mortar.  The limy soil on top of the escarpment was ideal for raising crops and dairy cows.
Niagara Escarpment

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