Lake Erie was gouged out by glacial ice between 1 million and 12,600 years ago.
It was one of the first Great Lakes to be uncovered during the last retreat of the glacial ice.
The oldest rocks from which the Lake Erie basin was carved are about 400 million years old and formed in a tropical ocean-reef environment.
Lake Erie and its shoreline are a major source of many minerals. The largest sandstone quarry in the world is located in Amherst, Lorain County, Ohio. Salt mines in Cuyahoga and Lake Counties extend out under Lake Erie and are an important source of revenue to the State. Sand, gypsum, and limestone used for construction purposes are found in abundance. Large reserves of natural gas, over 3 trillion cubic feet, are located under Lake Erie.
