The Great Lakes and Glaciers
Around a billion years ago, a fracture in the earth running from what is now Oklahoma to Lake Superior generated volcanic activity. It almost split North America. Over 20 million years, lava from the fracture flowed in this area. It created mountains covering the regions now known as northern Wisconsin and Minnesota and the Laurentian Mountains were formed in Eastern Canada. Occasional volcanic activity continued while these mountains eroded. Molten magma below the highlands of what is now Lake Superior spewed out to its sides causing the highlands to sink and form a huge rock basin that would one day hold Lake Superior. With time, the fracture stabilized and the rock tilted north to south.
This region went from fire to ice with the arrival of the glaciers. In fact, if you were to go back in time and visit Michi-gan 14,000 years ago, you would have found the Great Lakes area covered in a sheet of ice, called a glacier. These sheets averaged over one mile thick. At rates of only a little over a half foot per day, the glacier slowly made its way across the Great Lakes basin. It carved out deep valleys and moved large amounts of soil. As the glacier melted and moved towards Canada, it left behind a series of large holes that filled with meltwater from the glacier. These formed the basic shape of the Great Lakes. It wasn’t until around 6,000 years ago that the lakes took their final shape we see today.
Learn more about the history of the Great Lakes and Glaciers in today's All About Michigan!
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