How were the Great Lakes formed?
The Great Lakes basin is a relatively new phenomenon because it was formed by glacier activity only during the last 10,000 years. Geologically speaking, this is as short a time for the planet as a single second is out of your busy day! The foundation of the Lakes, however, was laid through several geologic eras spanning millions and millions of years. The continental glaciers repeatedly moved from what is now Canada over the Great Lakes region again and again as they thawed and melted, only to be later reformed. As these glaciers inched forward — some of them up to 2,000 meters (that’s about 6,500 feet) thick — they scoured the surface of the earth, leveled hills, and altered forever the previous ecosystem. Small valleys created by the river systems of the previous era were deepened and enlarged to form the basins for what are now the Great Lakes. Related references: TEACH: How the lakes were formed Great Lakes Atlas, 3rd ed. Two Natural Processes in the Great Lakes: Geology and Clim
. The last major glacier called the Laurentide formed. It covered almost all of Canada and extended to the United States as far as Chicago, Illinois. As it started melting and receding, it pushed against the land andmade big empty spaces. All the water that was left behind, called meltwater, filled those holes which made the Great Lakes. (This may help your child with homework.
