Glaciers

From 600-to- 230 million years ago, Monroe was on the bottom of a large shallow sea that covered much of central North America. Today a peek back to that time can be seen in the limestone rocks that form layers along the sides of the North Dixie Highway Underpass. These limestone rocks are the remains of that ancient sea. From about 500-250- million years ago, Monroe’s climate was probably much warmer than it is today because it was located father south. The seas eventually retreated and about a million years ago the first glaciers began advancing into the Midwest from Canada. Matter of fact, a little bit of Canada is under the feet of all Monroe residents.

Glaciers advanced into the Monroe area from Canada and carried sand, silt, clay, and boulders. These materials were left here permanently when the last of the glaciers retreated north and left the upper Midwest about 10,000 years ago. Geologists say glaciers that covered Monroe were up to a mile-high. The glaciers’ bulldozing power was so intense as they moved south that they gouged deep depressions and basins in the land. As the glaciers receded north from the Midwest, enormous amounts of meltwater from the glaciers filled the deep depressions — eventually forming Lake Erie and the four-other Great Lakes.