Lake Superior is a lake located in central North America. It is the northernmost, westernmost, and highest of the Great Lakes. The lake spans the Canada–United States border, with the Canadian province of Ontario to the north and east, and the U.S. states of Minnesota to the west, and Michigan and Wisconsin to the south. Lake Superior is the largest freshwater lake in the world by surface area and the third-largest freshwater lake by volume. Water from Lake Superior flows into Lake Huron through the St. Marys River, then continues through the lower Great Lakes, the St. Lawrence River, and finally into the Atlantic Ocean.
Name
The Ojibwe name for the lake is gichi-gami (in syllabic writing: ᑭᒋᑲᒥ), which means "great sea." In the poem The Song of Hiawatha, Henry Wadsworth Longfellow wrote the name as "Gitche Gumee." Gordon Lightfoot also used this spelling in his song "The Wreck of the Edmund Fitzgerald."
Other sources say the full Ojibwe name is Ojibwe Gichigami ("Ojibwe's Great Sea") or Anishinaabe Gichigami ("Anishinaabe's Great Sea"). A dictionary written in 1853 by Father Frederic Baraga, the first for the Ojibway language, lists the name as Otchipwe-kitchi-gami, which is how "Ojibwe Gichigami" is spelled in English letters.
In the 17th century, French explorers reached the lake through the Ottawa River and Lake Huron. They called it le lac supérieur, meaning "the upper lake" because it is higher in elevation than Lake Huron. Some Jesuit missionaries from the same time named it Lac Tracy after Alexandre de Prouville de Tracy. After the British took control of the area from the French in the 1760s, following the French and Indian War, they changed the lake's name to Superior, because it is larger than any other lake in that region.
Hydrography
Lake Superior flows into Lake Huron through the St. Marys River and the Soo Locks (Sault Ste. Marie locks). Lake Superior is the largest freshwater lake in the world by area and the third largest in volume, after Lake Baikal in Siberia and Lake Tanganyika in East Africa. The Caspian Sea is larger than Lake Superior in both surface area and volume, but it is slightly salty.
Lake Superior has a surface area of 31,700 square miles (82,000 km²), which is about the size of South Carolina or Austria. Its longest length is 350 miles (563 km) and its widest point is 160 miles (257 km). The average depth is 80.5 fathoms (483 ft or 147.2 m), and the deepest point is 222.17 fathoms (1,333 ft or 406.3 m). Lake Superior holds 2,900 cubic miles (12,100 km³) of water. If all the water in Lake Superior were spread evenly over North and South America, it would cover the land to a depth of 30 centimeters (12 inches). The shoreline of the lake is 2,726 miles (4,387 km) long, including islands. Lake Superior has a small ratio (1.55) of catchment area to surface area, which means it is influenced little by land.
In 1985, American limnologist J. Val Klump reached the deepest point of Lake Superior during a scientific expedition. This point is 122 fathoms 1 foot (733 ft or 223 m) below sea level, making it the second-lowest spot in the continental interior of the United States and the third-lowest in North America. Great Slave Lake in Canada is the deepest spot in North America at 1,503 ft (458 m) below sea level, and Iliamna Lake in Alaska is the second deepest at 942 ft (287 m) below sea level. Although Crater Lake in Oregon is the deepest lake in the United States, it is located at a higher elevation, so its deepest point is 4,229 ft (1,289 m) above sea level.
Lake Superior’s surface temperature changes with the seasons, but the water below 110 fathoms (660 ft or 200 m) stays nearly constant at 39°F (4°C). This temperature difference causes the lake to form layers, or stratify, seasonally. Twice a year, the entire lake mixes completely, and the water reaches the same temperature from top to bottom. This mixing makes the lake dimictic. Because of its large volume, water in Lake Superior stays in the lake for about 191 years before flowing out.
Storms on Lake Superior often produce waves over 20 feet (6.1 m) high. Waves exceeding 30 feet (9 m) have been recorded.
Lake Superior is fed by more than 200 rivers, including the Nipigon River, the St. Louis River, the Pigeon River, the Pic River, the White River, the Michipicoten River, the Bois Brule River, and the Kaministiquia River. The lake’s outlet at the St. Marys River has steep rapids. The Soo Locks allow ships to bypass the rapids and overcome the 25-foot (8 m) height difference between Lakes Superior and Huron.
The average surface elevation of Lake Superior is 600 feet (183 m) above sea level. Until about 1887, the natural flow through the St. Marys River rapids controlled the lake’s outflow. By 1921, structures like gates, locks, and canals were built to manage water flow. These structures are called the Compensating Works and follow a regulation plan called Plan 1977-A. Water levels, including water diverted from the Hudson Bay watershed, are managed by the International Lake Superior Board of Control, which was created in 1914 by the International Joint Commission.
Lake Superior’s water level reached a record low in September 2007, slightly lower than the previous record low in 1926. Water levels returned to normal within a few days.
Lake Superior’s water levels change monthly, with the highest levels in October and November. The normal high-water mark is 1.17 feet (0.36 m) above the datum (601.1 ft or 183.2 m). In the summer of 1985, Lake Superior reached its highest recorded level at 2.33 feet (0.71 m) above the datum. In 2019 and 2020, the lake set new high-water records in nearly every month.
The lowest water levels occur in March and April. The normal low-water mark is 0.33 feet (0.10 m) below the datum. In the winter of 1926, Lake Superior reached its lowest recorded level at 1.58 feet (0.48 m) below the datum. The low water levels in 1926 followed a year of record lows in 1925, with water levels ranging from 1.58 to 0.33 feet (0.48 to 0.10 m) below the datum from October 1925 to June 1926. In the summer of 2007, monthly low-water records were set, with August at 0.66 feet (0.20 m) and September at 0.58 feet (0.18 m) below the datum.
A study by professors at the University of Minnesota Duluth found that Lake Superior may be warming faster than its surrounding area. Between 1979 and 2007, summer surface temperatures in the lake increased by about 4.5°F (2.5°C), compared to an increase of about 2.7°F (1.5°C) in the surrounding air temperature. This warming may be linked to less winter ice cover, which allows more sunlight to warm the water. If current trends continue, Lake Superior, which freezes completely once every 20 years, could become ice-free more often by 2040. However, recent data through 2021 does not support this prediction.
Warmer temperatures may increase snowfall in the lake-effect snow belts near the lake, especially in the Upper Peninsula of Michigan. In 2013–2014 and 2014–2015, high ice coverage was recorded across the Great Lakes. On March 6, 2014, ice coverage peaked at 92.5%, the second-highest level in recorded history. In 2019, Lake Superior’s ice coverage reached 95%, surpassing the 2014 record.
Geography
The largest island in Lake Superior is Isle Royale in Michigan. Isle Royale has many lakes, some of which also have islands. Other well-known islands include Madeline Island in Wisconsin, Michipicoten Island in Ontario, and Grand Island (the location of the Grand Island National Recreation Area) in Michigan.
Larger cities near Lake Superior include the twin cities of Duluth, Minnesota, and Superior, Wisconsin; Thunder Bay in Ontario; Marquette in Michigan; and the twin cities of Sault Ste. Marie in Michigan and Sault Ste. Marie in Ontario. Duluth-Superior, located at the western end of Lake Superior, is the farthest inland point on the Saint Lawrence Seaway and the farthest inland port in the world.
Scenic places along Lake Superior include Apostle Islands National Lakeshore, Brockway Mountain Drive on the Keweenaw Peninsula, Isle Royale National Park, Porcupine Mountains Wilderness State Park, Pukaskwa National Park, Lake Superior Provincial Park, Grand Island National Recreation Area, Sleeping Giant (Ontario), and Pictured Rocks National Lakeshore. The Great Lakes Circle Tour is a special road system that connects all of the Great Lakes and the St. Lawrence River.
Climate
Lake Superior's large size lessens how extreme the seasons are in its humid continental climate, which is also found in places like Nova Scotia. The lake's surface warms up and cools down slowly, with temperatures between 32 and 55 degrees Fahrenheit (0 and 13 degrees Celsius) around 1970. This helps keep summer air temperatures cooler with frequent sea breezes and makes winter air temperatures less severe, while also causing heavy snowfall near the lake during cold months. Hills and mountains near the lake trap moisture and fog, especially in the fall.
Geology
The rocks along Lake Superior's northern shore are among the oldest on Earth. During the Precambrian time period (4.5 billion to 540 million years ago), molten rock called magma rose to the surface, forming the intrusive granites of the Canadian Shield. These ancient granites are still visible on the North Shore today. During the Penokean orogeny, a mountain-building event that helped form the Great Lakes tectonic zone, valuable metals were deposited in the area. The region around Lake Superior is rich in minerals, including copper, iron, silver, gold, and nickel. Notable mining sites include the Hemlo gold mine near Marathon, copper from the Keweenaw Peninsula and the Mamainse Point Formation, iron from the Gogebic Range, silver at Silver Islet, and uranium at Theano Point.
Over time, mountains in the area eroded, and layers of sediment were deposited. These sediments hardened into rocks such as limestone, dolomite, taconite, and shale found at Kakabeka Falls. Later, the continental crust split, creating one of the deepest rifts on Earth. Lake Superior now lies within this long-extinct Mesoproterozoic rift valley, called the Midcontinent Rift. Magma injected between sedimentary rock layers formed hard diabase sills. These diabase layers protect the sedimentary rocks below, creating flat-topped mesas in the Thunder Bay area. Amethyst, a type of purple quartz, formed in some cavities created by the Midcontinent Rift. Several amethyst mines are located in the Thunder Bay region.
Lava from the rift formed black basalt rock found on Michipicoten Island, the Black Bay Peninsula, St. Ignace Island, and Isle Royale.
In the most recent geological period, during the Wisconsin glaciation 10,000 years ago, a thick layer of ice covered the region, reaching 1.25 miles (2.01 km) in depth. The movement of this ice sheet shaped the land's current features. As the ice melted, it left behind deposits of gravel, sand, clay, and boulders. Glacial meltwater collected in the Superior basin, forming Lake Minong, an earlier version of Lake Superior. When the ice's weight was removed, the land rose, and a drainage path formed at Sault Ste. Marie, which became today's St. Mary's River.
History
The first people arrived in the Lake Superior region about 10,000 years ago after glaciers from the Last Glacial Period melted. These early people, called the Plano, hunted caribou using spears with stones on the northwestern side of Lake Minong. Around 5000 BC, the Shield Archaic peoples came to the area. Evidence of their culture has been found at the eastern and western ends of the Canadian shore. They used bows and arrows, paddled dugout canoes, fished, hunted, mined copper for tools and weapons, and created trading networks. These people are believed to be the direct ancestors of the Ojibwe and Cree. The Laurel complex people (about 500 BC to AD 500) developed seine net fishing, as shown by findings near rivers like the Pic and Michipicoten. The Terminal Woodland period people lived in the area from AD 900 to 1650. They were Algonquian peoples who hunted, fished, and gathered berries. They used snowshoes, birch bark canoes, and conical or domed lodges. At the mouth of the Michipicoten River, nine layers of encampments have been found. Most of the Pukaskwa Pits were likely made during this time.
The Anishinaabe people (including the Ojibwe/Chippewa) have lived in the Lake Superior region for more than 500 years. They were preceded by the Dakota, Meskwaki (Fox), Menominee, Nipigon, Noquet, and Gros Ventres. After Europeans arrived, the Anishinaabe became middlemen between French fur traders and other Native peoples. They became the dominant Native group in the region, forcing out the Sioux and Fox and defeating the Iroquois near Sault Ste. Marie in 1662. By the mid-1700s, the Ojibwe occupied all of Lake Superior’s shores.
In the 1700s, the fur trade supplied Europe with beaver hats. The Hudson’s Bay Company had control of the region until 1783, when the competing North West Company was formed. The North West Company built forts on Lake Superior at Grand Portage, Fort William, Nipigon, the Pic River, the Michipicoten River, and Sault Ste. Marie. By 1821, the two companies merged under the Hudson’s Bay Company name. Many towns near the lake are now or were once mining areas, or involved in processing or shipping. Today, tourism is a major industry, as the lake’s rugged shorelines and wilderness attract visitors.
Lake Superior has been important for the Great Lakes Waterway, helping transport iron ore, grain, and other materials. Large ships called lake freighters and smaller ocean freighters move these goods across the lake. Shipping to Lake Superior started slowly in the 1800s. The first steamboat on the lake was the Independence in 1847, while steamers on other Great Lakes began earlier, in 1816. Ice closes the lake to shipping from mid-January to late March, with exact dates varying yearly based on weather.
The southern shore of Lake Superior between Grand Marais, Michigan, and Whitefish Point is called the "Graveyard of the Great Lakes" because more ships have been lost near Whitefish Point than anywhere else on the lake. These shipwrecks are protected by the Whitefish Point Underwater Preserve. Storms that caused many ship losses include the Mataafa Storm in 1905 and the Great Lakes Storm of 1913.
The wreckage of the SS Cyprus—a 420-foot ore carrier that sank in 1907 during a storm—was found in 2007. Built in Lorain, Ohio, the Cyprus sank on its second voyage while carrying iron ore from Superior, Wisconsin, to Buffalo, New York. Only one crew member survived. In 1918, French minesweepers Inkerman and Cerisoles sank during a Lake Superior storm, possibly after hitting an uncharted reef. This event caused the largest loss of life on the lake, with 78 crew members dying.
The SS Edmund Fitzgerald was the last ship to sink in Lake Superior, 15 nautical miles from Whitefish Point during a storm on November 10, 1975. The wreck inspired Gordon Lightfoot’s song "The Wreck of the Edmund Fitzgerald." All 29 crew members died, and no bodies were recovered. The ship split in half and lies at a depth of 88 fathoms.
Lightfoot’s song refers to Lake Superior’s cold water, which averages below 36°F (2°C). Cold water slows bacterial growth, preventing bodies from floating to the surface. In 1994, an explorer found a man’s body near the Edmund Fitzgerald’s pilothouse, fully clothed and wearing a life jacket.
In February 2024, wreckage from the SS Arlington, which sank in 1940, was discovered.
Ecology
Lake Superior is home to more than 80 types of fish. Fish that naturally live in the lake include banded killifish, bloater, brook trout, burbot, cisco, lake sturgeon, lake trout, lake whitefish, longnose sucker, muskellunge, northern pike, pumpkinseed, rock bass, round whitefish, smallmouth bass, walleye, white sucker, and yellow perch. Many other fish species have been brought to the lake either on purpose or by accident, such as Atlantic salmon, brown trout, carp, chinook salmon, coho salmon, freshwater drum, pink salmon, rainbow smelt, rainbow trout, round goby, ruffe, sea lamprey, and white perch.
Lake Superior has fewer nutrients dissolved in its water compared to the other Great Lakes. This makes it less productive for supporting fish populations, and it is classified as an oligotrophic lake. This is because the land surrounding the lake has underdeveloped soils, and the area has a small human population and limited agriculture. However, nitrate levels in the lake have been increasing steadily for more than 100 years. These levels are still below amounts that would harm human health, but the long-term rise shows an unusual pattern of nitrogen buildup. Scientists believe this may be linked to human activities that affect the nitrogen cycle, though the exact causes remain unclear.
Like other Great Lakes, fish populations in Lake Superior have been affected by the introduction of non-native species, such as the sea lamprey and Eurasian ruffe. These introductions often happened when natural barriers between the Great Lakes were removed to improve navigation. Overfishing has also contributed to declines in fish numbers.