More Peninsula Geology

Door County’s rocky promontories are typical of the bay side of the peninsula. This rock formation is the Niagara Escarpment – that tough dolostone that even multiple glaciations failed to wear-down.

This formation was formed during the Silurian age by tropical seas when Wisconsin was located much closer to the equator.

Plate tectonics can move a continent a handful of centimeters each and every year. Year–in and year-out. Before too long (roughly 420 million years) you might find yourself not on the equator but on the 45th parallel – midway between the equator and the North Pole.

Anyway, the glaciers that once occupied this part of Wisconsin only a mere 10,000 years ago eventually receded. That’s not to imply that they turned around and went back to the polar ice cap. Rather they melted in-place leaving their melt water as a vast endowment that filled the Great Lakes.

Lake levels back in those days were considerably higher than they are today. As evidence of that if you are observant you will find beaches, beach cobbles and sea caves quite distant from the current shoreline and many feet higher in elevation.

In the second picture there is a sea cave just above the talus slope of this rocky cliff. It was formed by the pounding of wave action over many, many years.

It also happens to be roughly 50 feet above the current lake level.

Only about 1 percent of Lake Michigan’s water is recharged by precipitation each year.

Lake levels fluctuate.

They always have.

They always will.