Ask anyone about the Great Lakes and chances are most will recall the mnemonic device taught in school to remember their names: “HOMES,” which stood for Huron, Ontario, Michigan, Erie, and Superior. But unless those students lived in a state that bordered these lakes, they may not have learned much about them beyond a cursory geography lesson.

It’s time to change that with a few cool facts you can use to wow guests at your next dinner party.

The Largest Body of Freshwater on Earth

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When combined, the Great Lakes equals one-fifth of the planet’s total freshwater supply. That’s a mind-boggling 6 quadrillion gallons of water. Consider this: these five lakes are over 95,000 square miles of combined area with a total span of 750 miles. This means that the lakes are larger than the United Kingdom. The Great Lakes are so large that they’ve earned the nickname as “the nation’s fourth seacoast” even though four of the five lakes are bordered by both Canada and the United States. Lake Michigan is the only lake that is completely within U.S. borders.

Larger Than You Think

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Here are a few size-related quick facts to give you a bit of perspective on the scale and size of the Great Lakes.

  • They are so large that their combined shoreline is almost equal to half the circumference of our planet.
  • A drive completely around all five lakes would take 6,500 miles or 108 hours. And there are official Circle Tours you can book and complete in four and a half days.
  • If you were able to remove all of the water from the Great Lakes and spread it evenly across the U.S., the entire country would be covered in 10 feet of water.
  • Technically, Superior, Michigan, and Huron are one body of water connected by the Straits of Mackinac.  
  • Lake Superior is the largest lake. It’s so large that all the other Great Lakes could easily fit into it, with room for three more lakes the size of Erie.

Experts Agree That the Great Lakes Are Really Seas

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Even though we think of these five bodies of water as lakes because they’re freshwater, they exhibit many behaviors associated with seas. For example, the Great Lakes experience tides twice a day. All five lakes are actually connected via channels and have a constant current that cycles water between each lake starting from the farthest, westward lake, Lake Superior. Water flows from Superior toward Michigan, Huron, and into Erie. From here, the water flows over Niagara Falls into Lake Ontario and out to the Atlantic Ocean by way of the St. Lawrence River.

Depending on the depth of each lake, experts have found that the time required to fully replace all of the water in a lake, or retention time, can vary from a couple of years to centuries. Because Superior is so large, its retention time is 194 years. However, the smallest, Erie, has a retention of just over two and a half years. Ontario’s retention is six years, followed by Huron at 22 years, and finally Michigan with 77 years.

You Can Sail From Lake Superior to the Atlantic Ocean

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Long before the Wright brothers made flight an option, people used waterways to get from point A to point B. This waterway has been in use since the days of the Vikings and became extremely popular with early settlers as a convenient sailing route to ship goods between coastal cities and points inland. In the earliest days of the U.S., traveling from, say, New York Harbor to Minnesota was a serious time commitment that could take weeks.

These days, thanks to modern sailing technology and an established canal and locks system, an adventurous person can leave from Duluth, Minnesota, in Lake Superior and reach the Atlantic Ocean in roughly eight and a half days. However, sailing experts agree that it is far easier to travel from Superior out towards the Atlantic Ocean versus the reverse direction. Because the lake currents run west to east, boats experience less resistance than when traveling east to west.

The Great Lakes Are Vital to Our Livelihoods

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This isn’t hyperbole. The Great Lakes doesn’t just represent 20 percent of the world's and 84 percent of North America’s freshwater supply. An estimated 40 million people who live in the Great Lakes region rely on these bodies for their water. Beyond providing a critical resource, these lakes also support fisheries and shipping, with 125 million tons of cargo passing through the Great Lakes’ shipping lanes every year carrying primarily agricultural products and iron ore. And most importantly, The Great Lakes represent a vital ecosystem that is home to over 3,500 species of plants and animals.

So, the next time you’re looking to flex your brain power and impress friends or family with interesting facts, start with the Great Lakes. Often overshadowed by the Atlantic and Pacific oceans, these lakes are a vital part of life for millions of people living in North America.