Glaciers
Michigan was formed by glacial erosion. Geologists think the erosion may have occurred more than 700,000,000 years ago when huge glaciers descended from the Arctic. Much of the rock and sediment around and under the Great Lakes was left behind when the glaciers melted.
Glaciers could have been from a half mile to one mile thick. Millions of years ago, the weight of the ice crushed and scraped the earth to form valleys and slopes. The softer the ground underneath the glacier, the more erosion. When the climate became warmer, the glaciers melted. The water drained into the deep groves that cut through the land. These became lakes.
This map is adapted from a surface geology map of the Kalamazoo-Black-Macatawa-PawPaw River Basin from A Water and Land Resource Plan for the Kalamazoo-Black-Macatawa-PawPaw River Basin
This map shows what glaciers left behind in the Kalamazoo area. The material carried by the ice is deposited whenever the ice melts. These glacial deposits are of two l types, till and outwash. Glacial till is material deposited directly by the ice and is unsorted and unstratified. It is a mixture of all shapes and sizes of rock. Moraine is till deposits which are made up of hills and depressions. Many times the depressions contain small lakes or ponds. Outwash is the the sorted and stratified material laid down by glacial meltwaters.
Sources:
A Water and Land Resource Plan for the Kalamazoo-Black-Macatawa-PawPaw River Basin, Citizens' Advisory Council, County Task Force, DNR, USDA
Kalamazoo County Geology and Environment, Western Michigan University Departments of Geology, Geography and Biology
by Molly and Sarah
