<P> The Great Lakes (French: les Grands - Lacs), also called the Laurentian Great Lakes and the Great Lakes of North America, are a series of interconnected freshwater lakes located primarily in the upper mid-east region of North America, on the Canada--United States border, which connect to the Atlantic Ocean through the Saint Lawrence River . They consist of Lakes Superior, Michigan, Huron (or Michigan--Huron), Erie, and Ontario . </P> <P> The Great Lakes is the largest group of freshwater lakes on Earth by total area, and second largest by total volume containing 21% of the world's surface fresh water by volume . The total surface is 94,250 square miles (244,106 km), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km), a bit less than the volume of Lake Baikal (23,615 km3). Due to their sea - like characteristics (rolling waves, sustained winds, strong currents, great depths, and distant horizons) the five Great Lakes have also long been referred to as inland seas . Lake Superior is the second largest lake in the world by area, and Lake Michigan is the largest lake that is entirely within one country . </P> <P> The Great Lakes began to form at the end of the last glacial period around 14,000 years ago, as retreating ice sheets exposed the basins they had carved into the land which then filled with meltwater . The lakes have been a major highway for transportation, migration, and trade, and they are home to a large number of aquatic species . Many invasive species have been introduced due to trade, and some threaten the region's biodiversity . </P>

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