What created the Great Lakes? glaciers earthquake rivers folding

The Great Lakes, which include Lakes Superior, Michigan, Huron, Erie, and Ontario, were primarily created by the action of glaciers. During the last Ice Age, which peaked around 20,000 years ago, thick ice sheets covered much of what is now Canada and the northern parts of the United States. As the climate began to warm, these ice sheets started to melt and retreat. The glaciers carved out deep basins in the Earth's crust from the pressure and scraping of ice advancing and retreating over the land. When the ice finally melted away, these basins filled with water, forming the Great Lakes.

The process of glacier formation and melting also involved a series of advances and retreats (glacial periods and interglacial periods), and with each advance and retreat, the glaciers reshaped the landscape further. Glacial till, a debris of rocks and soil left behind, was also instrumental in shaping the surrounding environments and creating the fertile lands around the lakes.