Lake Superior is the largest lake in North America, covering about 82,100 km² — more surface than any other freshwater lake on Earth. The rest of the top ten, by surface area, are Lake Huron, Lake Michigan, Great Bear Lake, Great Slave Lake, Lake Erie, Lake Winnipeg, Lake Ontario, Lake Nicaragua and Lake Athabasca.
Five of those ten lakes are shared between Canada and the United States or lie wholly in one of them, three sit in Canada's Northwest Territories or the Prairie provinces, and one is in Central America, which geographers count as part of the North American continent. Almost all of them owe their basins to ice: the last glaciation scoured the soft rock around the old Canadian Shield, and the meltwater filled the holes. Only Lake Nicaragua, in a tectonic depression ringed by volcanoes, breaks the pattern.
Ranked: The Ten Largest Lakes by Surface Area
The figures below are the commonly published surface areas. They vary slightly between agencies, because lake levels rise and fall and because some sources include islands while others do not, but the order is stable.
The gap between third and fourth place is the striking feature of the list. Lake Michigan is nearly twice the size of Great Bear Lake, and the three upper Great Lakes together cover close to 200,000 km², roughly the area of Senegal. Below them, five lakes cluster between about 19,000 and 31,000 km², and then the list drops sharply again to Nicaragua and Athabasca at around 8,000 km².
Superior, Huron and Michigan: The Upper Great Lakes
Lake Superior is shared by Ontario, Minnesota, Wisconsin and Michigan. Its basin sits on the ancient Midcontinent Rift, a 1.1-billion-year-old crack in the continent that never finished opening, and glaciers later deepened it to a maximum depth of about 406 m. That depth gives it a volume of roughly 12,000 km³, more than the other four Great Lakes combined, and enough water to cover North and South America to a depth of around 30 cm. Water entering Superior stays, on average, close to two centuries before leaving through the St. Marys River at Sault Ste. Marie.
Lake Huron, second on the list, has the longest shoreline of the Great Lakes once its islands are counted, largely because of Manitoulin Island — at about 2,766 km² the largest island in any freshwater lake — and the island-studded Georgian Bay on its Ontario side. Lake Michigan, third, is the largest lake lying entirely within one country, wrapping around Chicago, Milwaukee and the dune coast of western Michigan.
Hydrologists point out that Huron and Michigan are really one body of water. They meet through the Straits of Mackinac, a channel about 8 km wide and deep enough that the two lakes share the same surface level. Treated as a single lake, Michigan–Huron covers about 117,600 km² and would outrank Superior. Almost every published ranking keeps them separate, following historical naming rather than hydrology.
Great Bear and Great Slave: Arctic Lakes of the Canadian Shield
Great Bear Lake, in the Northwest Territories, is the largest lake entirely within Canada. The Arctic Circle crosses its northern arms, and it is frozen for roughly eight months of the year. Its only permanent community is Délı̨nę, a Sahtu Dene settlement at the head of the Great Bear River. Between 1932 and the early 1960s, the Port Radium mine on its eastern shore produced radium and then uranium, including ore used in the Manhattan Project — a legacy the community has pressed the federal government to address for decades.
Great Slave Lake, a few hundred kilometres to the south, is the deepest lake in North America at about 614 m. Yellowknife, the territorial capital, stands on its north shore, and in winter an ice road crosses Yellowknife Bay to the Dene community of Dettah. The lake drains west into the Mackenzie River, which carries its water 1,700 km to the Beaufort Sea. Both lakes sit on the boundary between the hard granite of the Canadian Shield and the softer sedimentary rock of the Interior Plains, which is exactly where the ice sheets found it easiest to excavate.
Erie, Winnipeg and Ontario: Shallow, Busy and Downstream
Lake Erie
Erie is the shallowest of the Great Lakes, with an average depth of only about 19 m and a maximum of 64 m. That makes it the warmest and the most biologically productive, supporting the largest commercial freshwater fishery in the Great Lakes, but also the most vulnerable to algal blooms fed by farm runoff from the Maumee River basin. In August 2014 a toxic bloom forced the city of Toledo, Ohio, to tell several hundred thousand residents not to drink their tap water for three days.
Lake Winnipeg
Lake Winnipeg in Manitoba covers 24,514 km² but averages only around 12 m deep. It is the largest surviving remnant of glacial Lake Agassiz, a meltwater lake that around 10,000 years ago covered more of the continent than all of today's Great Lakes combined. Lakes Manitoba and Winnipegosis, and Lake of the Woods on the Ontario border, are fragments of the same vanished lake. Winnipeg drains north through the Nelson River to Hudson Bay, and its outflow is heavily used for hydroelectric power.
Lake Ontario
Ontario is the smallest Great Lake by area but deeper than Erie, reaching 244 m. It receives Erie's water after the Niagara River drops about 99 m along its course, including the plunge over Niagara Falls. Ships bypass the drop through the eight locks of the Welland Canal, and Ontario's outflow becomes the St. Lawrence River at Kingston.
Lake Nicaragua and Lake Athabasca: The Outliers on the List
Lake Nicaragua, known locally as Cocibolca, is the largest lake in Central America at about 8,264 km². Unlike the glacial lakes to the north, it lies in a rift-like lowland along the volcanic arc of the Pacific coast. Ometepe, an island formed by two volcanoes — Concepción and Maderas — rises from its waters, and the archipelago of Las Isletas near the colonial city of Granada counts several hundred small islands. Bull sharks enter the lake from the Caribbean by swimming up the San Juan River, one of very few places where sharks live in a freshwater lake. Several proposals for an inter-oceanic canal, most recently a concession granted in 2013, planned to route ships across the lake; none has been built.
Lake Athabasca, straddling the Alberta–Saskatchewan border, completes the top ten. Fort Chipewyan on its western shore, founded in 1788 as a fur-trading post, is one of the oldest continuously inhabited European settlements in Alberta. The lake's south shore holds the Athabasca Sand Dunes, among the most northerly active dune fields on Earth, protected as a provincial park in Saskatchewan.
Area Versus Volume: How Baikal and Victoria Compare
Ranking by surface area flatters shallow lakes. Measured by volume, North America's picture changes and so does its standing in the world.
- Lake Victoria in East Africa covers about 59,950–68,800 km² depending on the source, so even at its largest it is smaller than Superior; it is also shallow, averaging around 40 m, and holds only about a quarter of Superior's water.
- Lake Baikal in Siberia covers only about 31,500 km², roughly the size of Great Bear Lake, yet it holds around 23,600 km³ — more than all five Great Lakes combined, which total about 22,700 km³. Its maximum depth of 1,642 m is more than four times Superior's.
- The Caspian Sea, at about 371,000 km², dwarfs everything on the North American list, but it is saline and is usually ranked separately from freshwater lakes.
So Superior is the world champion by area among freshwater lakes, but by volume it ranks behind Baikal and Africa's Lake Tanganyika. The Great Lakes as a group still hold around a fifth of the world's fresh surface water, which is why the 2008 Great Lakes Compact bars almost all diversions of their water outside the basin.
Why Rankings Disagree
Readers comparing lists will find variations, and most come from three choices:
- Splitting or joining Michigan–Huron. Joined, they form the largest lake on the continent and in the world by freshwater area.
- Counting reservoirs. Quebec's Manicouagan and Labrador's Smallwood Reservoir, created for hydroelectric dams, each cover several thousand square kilometres, and Smallwood at about 6,500 km² would rival Lake Athabasca if artificial lakes were admitted.
- Fluctuating lakes. Utah's Great Salt Lake has ranged from under 2,500 km² to more than 8,000 km² within living memory, so it may appear or vanish from lists depending on the year chosen.
Whatever list you use, the top three never change: Superior, Huron and Michigan are in a league of their own. For a closer look at the biggest of them, our guide to Lake Superior's geography covers its shoreline and shipping, while the Great Bear Lake guide explores the far north. If Central America's giant caught your interest, the Lake Nicaragua guide explains its volcanic islands, and you can see how Superior measures up against Siberia's ancient lake in Lake Baikal vs Lake Superior.