Did the Great Lakes used to be an ocean?

The story of the Great Lakes began over 1 billion years ago, when the ancient supercontinent Laurentia began splitting in half. Over the course of about 10 million years, the Midcontinent Rift System opened a massive fissure on its way to becoming a new ocean basin.



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Thousands of years ago, the melting mile-thick glaciers of the Wisconsin Ice Age left the North American continent a magnificent gift: five fantastic freshwater seas collectively known today as the Great Lakes — Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario.

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Distance from the Atlantic Ocean to Duluth, Minnesota via Lake Superior is 2,038 nautical miles and takes 8.5 sailing days. Since 1959, more than 2.5 billion tons of cargo (estimated at $375 billion!) have moved to and from the Canada, the United States, and 50+ other nations.

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Geology of Lake Inferior Lake Inferior is an underground lake that is located beneath Lake Superior. It is believed to be formed by a process known as karstification, which is the dissolution of limestone and dolomite rock. This process creates sinkholes, caves, and underground rivers and lakes.

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Lake Superior is the Cleanest and Clearest Great Lake Because of its somewhat isolated location and long cold winters, not much farming is done along Superior's shores. This means lower amounts of nutrients, sediments, and organic material are floating around the lake.

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Lake Superior is the world's largest freshwater lake by area (31,700 mi2 /82,100 km2). It is also the coldest and deepest of the Great Lakes, with a maximum depth of 406 meters (1,332 feet). By most measures, it is the healthiest of all the Great Lakes.

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How did the Great Lakes get so deep? The Great Lakes are deep due to the heavy glaciers slowly moving north over time. The weight of these glaciers caused the now Great Lakes to become deeper as they moved.

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Lake Superior holds a massive volume of water because of its enormous inland basin and the hundreds of rivers that feed it.

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True tides—changes in water level caused by the gravitational forces of the sun and moon—do occur in a semi-diurnal (twice daily) pattern on the Great Lakes. Studies indicate that the Great Lakes spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters in height.

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Lake Erie is the fourth-largest lake in North America (by surface area) and the eleventh-largest worldwide. It is the Great Lakes' southernmost, shallowest, and smallest by volume. By the 1960s, Lake Erie had become the most polluted of the Great Lakes, owing to the substantial industrial presence along its coasts.

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Lake Michigan The Great Lakes are all water bodies that swimmers should think twice about entering. Lake Michigan in particular is the roughest of the Great Lakes, and poses a major risk to those thinking of taking a dip. This body of water is often named the most dangerous lake in the United States.

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Lake Superior is the world's largest freshwater lake by area (31,700 mi2 /82,100 km2). It is also the coldest and deepest of the Great Lakes, with a maximum depth of 406 meters (1,332 feet).

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Lake Michigan wrecks: the oldest and the mostest Lake Michigan contains more shipwrecks than any of the other Great Lakes, as well as the oldest recorded one: the French ship Griffon, the first European vessel to sail the Lakes.

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Lake sturgeon are the largest fish in Lake Superior. They are among the oldest fish in the lake too. Did you know that a lake sturgeon can live to be older than 100 years? This species of fish has also been around for a long time—about 150 million years.

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Overall, the answer is yes. Lake Superior is safe for swimming.

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There is an abundance of life and different creatures you might find in Lake Michigan. Whales just aren't one of them. See all of the animals you can find in the lake here.

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Water in the Great Lakes comes from thousands of streams and rivers covering a watershed area of approximately 520,587 square kilometres (or 201,000 square miles).

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