•March 27, 2024•

What Did a Trillion Tons of Glacial Ice Do to Moultrie County?

by Janet Roney

Well, duh…it flattened it, of course. But, that’s not all it did.  

When the Wisconsin Glacier came down from Canada 30,000 years ago or so, it brought tons and tons of dirt, gravel, rocks, and sand with it that it picked up along the way. When global warming began 14,000 – 18,000 years ago and melted the ice, it left up to 200 feet of this debris, called glacial till, on top of everywhere the glacier reached.  

The weight of the ice and glacial drift depressed the earth’s crust, and shifted the viscous mantle below it. Like a teeter-totter, its weight pushed up the surface of the ice-free areas south of it. When the ice melted, post-glacial rebound began and continues to this day. Every century, the elevation of northeastern and central Illinois is rising from 3 to 4 feet, while land to the south is lowering. Bridge builders have to pay attention to that fact.       

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