The Formation of the Great Lakes

The formation of the great lakes took place many years ago. The features of the great lakes aren't the same today as it was around 2 million years ago. The great lakes were formed many years ago during the ice age. About 1.6 million years ago was a period in the ice age known as Pleistocene Epoch. During this time era many areas of the earth and the North American continent was covered in ice. Almost 30% of the Earth's surface was covered with large sheets of ice known as glaciers. There were glaciers that covered Canada and states on the northern border such as Minnesota. The glaciers crushed many mountains as they moved and created many valleys. The glaciers also left behind land formations along with the glacial erosion. The great lakes were created by this erosion and melting of one glacier that existed around 100,000 to 14,000 years ago. The glacier covering Canada and most northern states was known as Laurentide.

Laurentide was very large and was about 4 kilometers thick. The glacier was at it's biggest around 18,000 years ago. After causing much of the North American and Canada's glacial erosion, Laurentide began to melt. The temperature began to get warmer and Laurentide began to grow smaller. As Laurentide started to melt, the melt water began to fill the valleys and leveled mountains as well as giant holes left in the earth's surface by the glaciers. When the great lakes were formed, they contained much more water than they do today. Their river outlets and routes had also changed while the glacier was melting. Eventually there was a clear route to the Atlantic Ocean where the water began to flow into. Eventually this caused the water levels to drop to the current levels they are at today.
Since the glaciers flattened out the land all around the great lakes, much of the land continues to rebound and grow. The land that is not suppressed by the glaciers anymore grows at a rate of 7.5 centimeters every 100 years.

Even though there is rebounding taking place there is still evidence of the glacial erosions. The shorelines of the great lakes began to also take formation. Most of the beaches and sand was formed from the uplifted sand being brought to the shore from the waves of the lakes. The sand formed dunes also on the lakes. The dunes were formed from sand bars that were created from the rivers, which cut off the bays from the lakes. The shore of the great lakes is important because it is home to many plants and animals. The beaches help to keep the food chain the same by giving migrating birds food to eat.