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How the Great Lakes were formed

A satellite image of Michigan (NASA)
A satellite image of Michigan (NASA)

This article first appeared the Morning Report newsletter. You can sign up for it here.

We take pride in our Great Lakes, but do you know how they originally formed? Hint: It's ice cold.

What's the deal with those giant puddles that surround the Mitten? You may know them as the Great Lakes. While we take the fresh water part of the lakes for granted, we also take their origins for granted. 

How the Great Lakes were formed

Simply put, the Great Lakes were created by glaciers. About 18,000 years ago, the Laurentide glacier covered most of Canada and the Northern U.S. As the glacier moved, it flattened mountains and carved valleys. It's estimated that the glacier was nearly 2.5 miles thick.

About 14,000 years ago, things began to warm and the Laurentide glacier started to melt. As it melted, water filled the huge holes carved by the glacier. This process took about 7,000 years! (And you complain about the commute on I-696!)

Take a look at this map breakdown showing the ice retreat and formation of the Great Lakes over thousands of years. This is from the US Army Corps of Engineers Detroit District:


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