"Even today the Great Lakes landscape is bouncing back from the glaciers that retreated 10,000 years ago.
A key question researchers recently sought to answer is whether that has anything to do with fluctuating lake levels.
Here’s how it might work: The massive ice sheets pushed down the earth’s crust like a person pressing on a basketball, said Grahame Larson, professor of geology at Michigan State University.
And when the ice is gone, the relatively pliable layer under the Earth’s rocky crust rebounds, though more slowly than the surface of a basketball. ...
In fact, the Great Lakes basin is still rebounding, but at different rates in different places."