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.
Located on the Niagara River, which drains Lake Erie into Lake Ontario, Niagara Falls has the highest flow rate of any waterfall in North America, with 700,000 gallons of water traveling down the falls every second.
The length of time that it takes for water in a lake to be completely replaced is called retention time. Each of the Great Lakes has a different retention time. Lake Superior's retention time is much longer than the others: 191 years compared to just 3 years for Lake Erie.
Lake sturgeon (Acipenser fulvescens) are an awesome sight. The largest fish in the Great Lakes, they can grow up to nine feet long and weigh more than 300 pounds.
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