Ask anyone about the Great Lakes and chances are, most can recall the mnemonic device "HOMES" they learned in school to remember the names Huron, Ontario, Michigan, Erie, and Superior. But unless you lived in a state that bordered these lakes, you might not have learned much about these vast bodies of water beyond a cursory geography lesson. Here are five surprising facts about the Great Lakes.
They Account for 1/5 of the Earth's Fresh Water
When combined, the volume of the Great Lakes equals one-fifth of the planet’s total freshwater supply. That’s a mind-boggling 6 quadrillion gallons of water. The five lakes cover over 95,000 square miles of combined area with a total span of 750 miles.
This means that together the lakes are larger than the entire United Kingdom. They 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.
They're Larger Than You Think
Here are a few size-related 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 Earth.
- A drive around all five lakes would take 6,500 miles or 108 hours. 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, Lakes Superior, Michigan, and Huron are one body of water connected by the Straits of Mackinac.
- Lake Superior is the largest lake of the five. It’s so large that all the other Great Lakes easily fit inside it, with room for three more lakes the size of Lake Erie.
They're Technically Seas
Although we think of these five bodies of water as lakes because they’re freshwater, they exhibit many characteristics associated with seas. For example, the Great Lakes experience tides twice a day. All five lakes are 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 one of the Great Lakes — retention time — can vary from a couple of years to centuries. Because Lake Superior is so large, its retention time is 194 years. However, the smallest of the Great Lakes, Lake Erie, has a retention time of just over two and a half years. Lake Ontario’s retention is six years, followed by Lake Huron at 22 years, and finally Lake Michigan at 77 years.
You Can Sail From Lake Superior to the Atlantic Ocean
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.
They're Vital to Our Livelihoods
This isn’t hyperbole. The Great Lakes don't just account for 20% of the world's and 84% of North America’s freshwater supply. An estimated 40 million people who live in the Great Lakes region rely on these bodies for water. Beyond providing a critical resource, the lakes also support fisheries and shipping, with 125 million tons of cargo passing through the Great Lakes’ shipping lanes each year — carrying primarily agricultural products and iron ore. And most importantly, the Great Lakes represent a vital ecosystem home to over 3,500 species of plants and animals.