You’ve seen the photos from space. Five massive, blue thumbprints pressed into the middle of a continent. People call them "inland seas," but honestly, that doesn't even come close to describing the scale. When you stand on the shore of Lake Superior in the middle of November, watching fifteen-foot waves hammer a jagged shoreline, it doesn't feel like a lake. It feels like a threat. It feels like an ocean that forgot to be salty.
The Great Lakes North America are a geological fluke. They hold about 21% of the world's surface fresh water. Think about that for a second. If you took all that water and spread it across the lower 48 states, the entire country would be under nearly ten feet of water. Most people think they’re just places for summer cabins or shipping ore, but the reality is much more chaotic and, frankly, a bit more dangerous than the postcards suggest.
The Superior Problem: More Than Just Cold Water
Lake Superior is the boss. It’s the largest freshwater lake in the world by surface area. It’s so big that it has its own localized weather systems. You’ll be driving through clear skies in Duluth, and twenty minutes later, you’re in a "lake-effect" snow squall that shuts down the highway. It’s moody.
The water is famously cold. Even in August, the surface temperature rarely climbs high enough to be called "comfortable." If you jump in, it’s a physical shock. This coldness is why the lake is a graveyard. Because the water is so frigid, it inhibits bacterial growth that would normally cause shipwrecks to break down or bodies to rise. Down in the depths, things stay preserved. The SS Kamloops, which went down in 1927, still has its cargo—and some say its crew—eerily intact in the darkness.
It’s deep, too. 1,333 feet at its lowest point. That’s enough to submerge the Empire State Building with room to spare.
The Weird Physics of Seiches
Most people understand tides. The moon pulls the ocean, the water goes out, the water comes in. Simple. The Great Lakes don't really have tides, at least not significant ones. Instead, they have seiches.
Imagine you’re holding a giant bowl of soup and you give it a sudden, sharp shove. The liquid sloshes to one side and stays high for a moment before rushing back. That’s a seiche. In 1954, a massive seiche on Lake Michigan caused an eight-foot wall of water to slam into the Chicago lakefront. People were swept off piers. It happens because of sudden changes in atmospheric pressure or strong winds pushing water to one end of the lake. When the wind lets up, the water "rebounds" to the other side.
You can be standing on a beach in Michigan and see the water level drop a foot in twenty minutes, only to have it come roaring back later. It’s unpredictable. It’s one of those things that makes these lakes feel alive in a way a smaller body of water just doesn't.
The Niagara Connection and the Flow
We tend to think of the Great Lakes North America as five separate puddles. They aren't. They are a single, slow-moving river system flowing from West to East.
👉 See also: Red Hook Hudson Valley: Why People Are Actually Moving Here (And What They Miss)
- Superior starts the party at the highest elevation.
- It drops through the St. Marys River into Huron and Michigan (which are technically the same lake hydrologically, connected by the five-mile-wide Straits of Mackinac).
- Then it drains into the much smaller, much shallower Lake Erie.
- From Erie, it takes a violent 160-foot plunge over Niagara Falls into Lake Ontario.
- Finally, it heads out the St. Lawrence River to the Atlantic.
Because Erie is so shallow—averaging only about 62 feet deep—it’s the "warm" lake. It’s also the most volatile. Shallow water kicks up faster in a storm. While Superior has long, rolling swells, Erie has short, choppy waves that can flip a boat before the captain even realizes the wind has shifted.
Invasive Species and the Changing Ecosystem
If you walk along a beach on Lake Lake Michigan today, you’ll probably see millions of tiny, striped shells. These are Zebra and Quagga mussels. They shouldn't be here. They hitched a ride in the ballast water of ocean-going tankers coming through the St. Lawrence Seaway in the 80s.
They’ve changed everything.
They filter the water so efficiently that the lakes are actually clearer than they were fifty years ago. This sounds like a good thing, right? Who doesn't want clear water? Well, the problem is that sunlight can now reach much deeper into the lake, which causes massive algae blooms that kill off native fish. They also strip out the plankton that forms the base of the food chain.
Then there’s the Sea Lamprey. It’s basically a swimming necktie with a mouth full of concentric circles of teeth. It latches onto trout and salmon and rasps a hole through their scales to drink their blood. In the 1940s and 50s, they nearly wiped out the lake trout population. We spend millions of dollars every year on "lampricide" treatments in tributary streams just to keep their numbers down. It’s an endless war.
The Wreck of the Edmund Fitzgerald: Not Just a Song
You can’t talk about the Great Lakes North America without mentioning the shipwrecks. There are estimated to be over 6,000 wrecks across the lakes, with some historians suggesting the number is closer to 10,000.
The most famous is the SS Edmund Fitzgerald.
Gordon Lightfoot wrote the song, but the reality was a lot grimmer. In November 1975, the "Fitz" was hauling iron ore pellets across Superior. It got caught in a massive storm with 25-foot waves and hurricane-force winds. The ship was over 700 feet long—a giant. It vanished from radar without a single distress call. To this day, nobody is 100% sure if she bottomed out on a shoal, took on water through the hatches, or was simply snapped in half by two massive waves.
✨ Don't miss: Physical Features of the Middle East Map: Why They Define Everything
The lake doesn't give up its dead. The search teams found the ship in two pieces at the bottom, but the 29 crew members were never recovered.
The Economic Engine Nobody Sees
While everyone focuses on the recreation, these lakes are basically a highway. The Great Lakes-St. Lawrence Seaway System connects the heart of the North American continent to the rest of the world.
Think about the steel in your car. There’s a good chance the iron ore for that steel came from the Mesabi Range in Minnesota, traveled by rail to Duluth, was loaded onto a 1,000-foot "Laker" ship, and sailed through the Soo Locks to a mill in Gary, Indiana, or Cleveland, Ohio.
The "Soo Locks" in Sault Ste. Marie are actually more vital than most people realize. If those locks went down for a significant amount of time, the North American steel industry would effectively grind to a halt. It’s a delicate, high-stakes logistical dance that happens every day from March to January, until the ice gets too thick to move.
Why Lake Michigan is Different
Lake Michigan is the only one of the five located entirely within the United States. It has the largest freshwater dunes in the world. If you go to Sleeping Bear Dunes, you’re looking at piles of sand hundreds of feet high that were dumped there by retreating glaciers 10,000 years ago.
It’s also home to some of the most sophisticated urban engineering on the planet. In the late 1800s, Chicago actually reversed the flow of the Chicago River. Instead of the river flowing into Lake Michigan (and polluting the city's drinking water with sewage), they dug a canal that forced the river to flow out of the lake toward the Mississippi River. It was a massive middle finger to geography, and it’s still one of the most controversial water-diversion projects in history.
The Salt Problem
In the last decade, scientists have started sounding the alarm about "freshwater salinization." Basically, we use so much road salt in the winter in places like Michigan, Wisconsin, and Ontario that the runoff is turning the lakes salty.
It’s not enough to taste it yet, but it’s enough to mess with the chemistry of the water. Some smaller inland lakes are already reaching salt levels that are toxic to native microscopic life. In the Great Lakes, the sheer volume of water dilutes it, but the trend line is heading in the wrong direction.
🔗 Read more: Philly to DC Amtrak: What Most People Get Wrong About the Northeast Corridor
How to Actually Experience the Lakes
If you want to understand the Great Lakes North America, don't just go to a crowded beach in Chicago or Toronto.
Go to the Upper Peninsula of Michigan. Go to a place called Pictured Rocks. The cliffs there are stained with minerals—iron, copper, manganese—creating streaks of red, green, and orange against the turquoise water. It looks like the Mediterranean, but the air smells like pine needles and the water is 45 degrees.
Take a ferry to Isle Royale. It’s one of the least-visited National Parks because it’s a rugged island in the middle of Lake Superior. There are no cars. Just moose, wolves, and a handful of hikers. It’s one of the few places left where you can see what the lakes looked like before we showed up with our freighters and our invasive mussels.
What Most People Get Wrong
People assume the Great Lakes are "safe" because there are no sharks or jellyfish.
Wrong.
The danger here is the weather and the currents. Rip currents on the Great Lakes are just as deadly as those on the Atlantic coast. Because the waves have a shorter "period" (the time between waves), you don't get a break. If you get knocked down, the next wave hits you before you can stand up. Every year, dozens of people drown because they underestimate how much energy is moving in that water.
Moving Forward: Your Great Lakes Checklist
If you’re planning to explore this region, you need to approach it with a bit of respect. It’s not a swimming pool.
- Check the Marine Forecast: Don't just look at the weather on your phone. Look at the "Small Craft Advisory" for the specific lake. If the NWS says stay off the water, stay off the water.
- Visit a Maritime Museum: The Great Lakes Shipwreck Museum at Whitefish Point is chilling. It houses the bell from the Edmund Fitzgerald. It puts the scale of these "lakes" into perspective.
- Watch the "Lake Effect": If you’re visiting in winter, understand that the "snow belt" is real. You can have three inches of snow in one town and three feet in the town ten miles away because of how the wind picks up moisture from the open water.
- Support Local Conservation: Groups like the Alliance for the Great Lakes work on keeping plastic and excess nutrients out of the water. With the threat of Asian Carp reaching the lakes through Chicago's canals, these organizations are the front line.
The Great Lakes aren't just a geographic feature. They are the lifeblood of an entire region, a source of drinking water for 40 million people, and a reminder that even in the middle of a continent, nature can still be vast, terrifying, and beautiful. Treat them like an ocean, because for all intents and purposes, they are.