These five lakes—Superior, Michigan, Huron, Erie, and Ontario—are actually the remnants of a once-greater prehistoric lake called Lake Algonquin.
Together the Great Lakes hold about 20 percent of the world’s freshwater. On the border of Canada and the United States, they are connected to each other and to the Atlantic Ocean by many rivers, canals, and the St. Lawrence Seaway, which allows major shipping to enter the continent’s interior.
Their combined surface area is more than 95,000 square miles (246,611 square kilometers).
This great size sometimes makes them act more like small oceans than lakes, with obvious tides, huge storms, currents, and accompanying shipwrecks.
The five Great Lakes border Canada and the United States. Lake Baikal in Siberia, a very deep lake, contains about the same amount of water as all of the Great Lakes combined, but it has only about one eighth of their surface area.