Michigan's Geological Landscape
The shaping of Michigan's geological landscape began more than one million years ago, during the great Ice Age. Her features were sculpted by four massive continental glaciers scouring across the Midwest. Michigan experienced the last great ice sheet, known as the Wisconsin Glacier, about fourteen thousand years ago. This huge ice mass was a mile thick and almost four million miles square. Its northernmost head touched Hudson Bay, and its icy tongue reached toward the banks of the Ohio River. As this "river of ice" crept over the underlying rocks, its base scraped millions of tons of earth like a giant bulldozer over the land. This debris composed of soil, pebbles, cobbles and boulders was pushed forward, grinding rocks into glacial dust, while boulders scratched their signatures on the bedrock.
Then the climate began to warm. Meltwater carried the soils and rocks away from the melting glacier, depositing its drift over the landscape. As this blend of soils and rocks was dropped away from the ice, the low hills, or moraines, were created across the state. Michigan's glacial drift averages 200 to 300 feet; however, the thickness of drift has measured over 1,000 feet in a few Michigan locations and is non-existent in others. The grinding of boulders created particles of various sizes and weights. The heaviest pieces fell first, forming stony ridges which formed the stream's flow direction and the edge of the glacier as it melted. Lighter materials were carried farther, dropping along the way as the flowing water slowed. These materials dried in sheets forming vast, flat multi colored areas of sand, silt, clay and a mixture of the three called outwash plains.
The weight of the glacier over the Michigan basin was lessening, and the earth began to rebound, like a sponge returning to its original shape when the squeezing stops. The Michigan landscape began to emerge like a slowly rising phoenix. Plants began to appear on the drying landscape. Communities formed as various plants found a suitable growing environment near each other.