The water reared up and slammed onto the sand like an ambush predator. Then it withdrew, and came back. Again and again the surf attacked the beach, and exploded over a nearby concrete breakwater. White gulls stood out against a dull sky as they fought to stay aloft in winds that had gathered strength over hundreds of miles of open water. The National Weather Service had issued a gale warning, an alert used only for marine locations. But this wind advisory wasn’t for the coast along Cape Cod or California, and the spray from the angry surf wasn’t salty. This stormy seaside scene unfolded on a spring day along the shores of a mere lake, far from the nearest ocean.
The Great Lakes of North America’s midsection—Superior, Michigan, Huron, Erie, and Ontario—together span nearly 100,000 square miles, with a combined coastline just shy of 10,000 miles. They hold more than a fifth of Earth’s unfrozen fresh water, straddle an international border, and help move more than $15 billion dollars worth of cargo each year. They even have their own U.S. Coast Guard district, the only lakes with such a distinction. And the Guard’s rescue teams stay busy: Superior and its siblings are capable of storm surges, rip currents, tsunamis, rogue waves, unique extreme weather phenomena, and destructive surf. They have claimed more than 6,000 ships, more than the Gulf of Mexico and the Black Sea combined, according to estimates. So should we really be calling them the Great Inland Seas?
“The most accurate answer you’re going to get is, ‘I don’t know,’” says John Richard Saylor, author of the upcoming Lakes: Their Birth, Life, and Death. “I do think it comes down to semantics, what you want to call a ‘sea.’”
For many, the Great Lakes are indeed greater than lakes. The United States Environmental Protection Agency, for example, describes them as “vast inland freshwater seas.” A seminal 2017 paper in Limnology and Oceanography, authored by some of the most influential researchers studying the lakes, also refers to them as ‘inland seas.’ But what makes a sea varies by source.
You might, for example, associate seas with saltwater, but “Whether water is salty or fresh does not cleanly separate lakes from seas,” says Robert Sterner, director of the Large Lakes Observatory at the University of Minnesota Duluth and one of the coauthors of the 2017 paper. “Many lakes are saline, some more so than the oceans. And the Baltic Sea is pretty fresh, especially near its headwaters.”
Generally speaking, seas are defined by size and borders—but, from there, things get murky. The U.S. National Oceanic and Atmospheric Administration (NOAA), for example, describes seas as smaller than oceans and at least partially bounded by land (the Sargasso Sea, in the center of the Atlantic Ocean and defined by surrounding currents, is an exception). Merriam-Webster has more than half a dozen definitions for the word “sea,” including “an inland body of water,” citing the Caspian Sea as an example. However, most scientists actually consider the Caspian a lake because it is surrounded by land with no connection to an ocean. “I generally say the Caspian Sea is not on the list of Earth’s large lakes mainly for cultural, not scientific, reasons,” says Sterner.
Let’s muddy the waters a bit more: The Dead Sea is a saltwater lake, and the Gulf of Mexico and Hudson Bay are both seas. Meanwhile, a growing number of scientists believe the Red Sea may actually be a young ocean.
Back in the Midwest, even the people who have known the Great Lakes the longest haven’t settled on exactly what they are. The lakes themselves began emerging more than 10,000 years ago when mile-high glaciers, which had carved basins and gashes into the land, retreated at the end of the last ice age. Meltwater filled depressions left behind, creating first marshy areas and then deeper bodies of water over several millennia—and humans were there to witness it. A 2021 paper in the journal PaleoAmerica described initial research at Belson, a site in Michigan that may be 13,000 years old and represents some of the earliest evidence of humans in the Great Lakes region. Also in 2021, in the journal PLOS One, another team of researchers described 9,000-year-old flakes of obsidian, evidence of toolmaking, found at the bottom of Lake Huron. Interestingly, the material’s chemical composition indicates that the volcanic glass originated in Central Oregon, about 2,500 miles to the west, hinting at extensive travel and trade networks across the continent at the time.
While the languages of these earlier people are not known, over the last few millennia the Great Lakes have been home to several Native American and First Nations peoples, most of which belong, culturally and linguistically, to the Anishinaabe. The term covers a number of communities dispersed over a broad and varied geographical area, but there is continuity among them in how the Great Lakes are perceived.
“I refer to Anishinaabe as a confederacy of different nations, which include Ojibwe, Potawatomi, and Odawa, but also Menominee, Saulteaux, Meskwaki, Kickapoo, Shawnee, Waabanaki—all of these tribes speak various dialects of the same language,” says Michael Waasegiizhig Price, a Wisconsin-based traditional ecological knowledge specialist for the Great Lakes Indian Fish & Wildlife Commission. Price notes that there are different dialects across the region, and varied orthographies—the ways a spoken language is written down, including spelling and capitalization. Each lake also has a specific name but, when talking generally about one of the Great Lakes, Anishinaabe people say gichigami, gichi-gami, or chigamiing, depending on dialect, which all translate as “big or great body of water.” Whether that means “lake” or “sea,” well … The Decolonial Atlas, which Price cites, refers to the Great Lakes as “the five freshwater seas,” but he takes exception to that.
“As for the word ‘sea,’ I believe this to be a colonial word that was brought here (by) Europeans,” he says. “Today, some Anishinaabe people refer to the Great Lakes as inland seas, but this is a new evolution in our language—English is impacting how we use our Indigenous language.”