Lake Superiorbathymetric map.[1][2][3] The deepest point, roughly off its southeastern shore, is marked with "×".[4] The deep trenches in its eastern part may have originated fromtunnel valleys.[5][6]
According to other sources, the full Ojibwe name isᐅᒋᑉᐧᐁ ᑭᒋᑲᒥOjibwe Gichigami ("Ojibwe's Great Sea") orᐊᓂᐦᔑᓈᐯ ᑭᒋᑲᒥAnishinaabe Gichigami ("Anishinaabe's Great Sea").[15] The 1853 dictionary byFather Frederic Baraga, the first one written for the Ojibway language, gives the Ojibwe name asOtchipwe-kitchi-gami (a transliteration ofOjibwe Gichigami).[14]
In the 17th century, the first French explorers approached the great inland sea by way of theOttawa River and Lake Huron; they referred to their discovery asle lac supérieur (the upper lake, i.e., above Lake Huron in elevation). Some 17th-centuryJesuit missionaries referred to it asLac Tracy (forAlexandre de Prouville de Tracy).[16] After taking control of the region from the French in the 1760s, following their defeat in theFrench and Indian War, the Britishanglicized the lake's name toSuperior, "on account of its being superior in magnitude to any of the lakes on that vast continent".[17]
Lake Superior empties into Lake Huron via the St. Marys River and theSoo Locks (Sault Ste. Marie locks). Lake Superior is the largest freshwater lake in the world by area and the third largest in volume, behindLake Baikal inSiberia andLake Tanganyika inEast Africa. TheCaspian Sea, while larger than Lake Superior in both surface area and volume, isbrackish.
Lake Superior's deepest point[4] on the bathymetric map[1]
Lake Superior has a surface area of 31,700 square miles (82,103 km2),[7] which is approximately the size ofSouth Carolina orAustria. It has a maximum length of 350statute miles (560 km; 300 nmi) and maximum breadth of 160 statute miles (257 km; 139 nmi).[8] Its average depth is 80.5fathoms (483 ft; 147 m) with a maximum depth of 222.17 fathoms (1,333 ft; 406 m).[7][8][9] Lake Superior contains 2,900 cubic miles (12,100 km3) of water.[7] There is enough water in Lake Superior to cover the entireland mass of North and South America to a depth of 30 centimetres (12 in).[b] The shoreline of the lake stretches 2,726 miles (4,387 km) (including islands).[7] The lake boasts a very small ratio (1.55) of catchment area to surface area, which indicates minimal terrestrial influence.[18]
AmericanlimnologistJ. Val Klump was the first person to reach the lowest depth of Lake Superior on July 30, 1985, as part of a scientific expedition, which at 122 fathoms 1-foot (733 ft or 223 m) below sea level is the second-lowest spot in the continental interior of the United States and the third-lowest spot in the interior of the North American continent afterGreat Slave Lake in the Northwest Territories of Canada (1,503 ft or 458 m below sea level) andIliamna Lake in Alaska 942 ft or 287 m. (ThoughCrater Lake is the deepest lake in the United States and deeper than Lake Superior, Crater Lake's elevation is higher and consequently its deepest point is 4,229 feet (1,289 m)above sea level.)
While the temperature of the surface of Lake Superior varies seasonally, the temperature below 110 fathoms (660 ft; 200 m) is an almost constant 39 °F (4 °C). This variation in temperature makes the lake seasonallystratified. Twice per year, however, thewater column reaches a uniform temperature of 39 °F (4 °C) from top to bottom, and the lake waters thoroughly mix. This feature makes the lakedimictic. Because of its volume, Lake Superior has aretention time of 191 years.[19][20]
Annual storms on Lake Superior regularly feature wave heights of over 20 feet (6 m).[21] Waves well over 30 feet (9 m) have been recorded.[22]
The lake's average surface elevation is 600 feet (183 m)[8][19] above sea level. Until approximately 1887, the natural hydraulic conveyance through the St. Marys River rapids determined the outflow from Lake Superior. By 1921, development in support of transportation and hydroelectric power resulted in gates, locks, power canals and other control structures completely spanning St. Marys rapids. The regulating structure is known as the Compensating Works and is operated according to a regulation plan known as Plan 1977-A. Water levels, including diversions of water from theHudson Bay watershed, are regulated by theInternational Lake Superior Board of Control, which was established in 1914 by theInternational Joint Commission.
Lake Superior's water level was at a new record low in September 2007, slightly less than the previous record low in 1926.[23] Water levels recovered within a few days.[24]
The lake's water level fluctuates from month to month, with the highest lake 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.[25] 2019 and 2020 set new high-water records in nearly every month.[25]
The lake's lowest 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.[25] Additionally, the entire first half of the year (January to June) included record low months. The low water was a continuation of the dropping lake levels from the previous year, 1925, which set low-water records for October through December. During the nine-month period of October 1925 to June 1926, water levels ranged from 1.58 to 0.33 feet (0.48 to 0.10 m) below Chart Datum.[25] In the summer of 2007 monthly historic lows were set; August at 0.66 feet (0.20 m), and September at 0.58 feet (0.18 m).[25]
According to a study by professors at the University of Minnesota Duluth, Lake Superior may have warmed faster than its surrounding area.[26] Summer surface temperatures in the lake appeared to have increased by about 4.5 °F (2.5 °C) between 1979 and 2007, compared with an approximately 2.7 °F (1.5 °C) increase in the surrounding average air temperature. The increase in the lake's surface temperature may be related to the decreasing ice cover. Less winter ice cover allows moresolar radiation to penetrate and warm the water. If trends continue, Lake Superior, which freezes over completely once every 20 years, could routinely be ice-free by 2040[27] although more current data through 2021 does not support this trend.[28]
Warmer temperatures could lead to more snow in thelake effect snow belts along the shores of the lake, especially in the Upper Peninsula of Michigan. Two recent consecutive winters (2013–2014 and 2014–2015) brought high ice coverage to the Great Lakes, and on March 6, 2014, overall ice coverage peaked at 92.5%, the second-highest in recorded history.[29] Lake Superior's ice coverage further beat 2014's record in 2019, reaching 95% coverage.[30]
Lake Superior's size reduces the severity of the seasons of itshumid continental climate (more typically seen in locations likeNova Scotia).[32] The water surface's slow reaction to temperature changes, seasonally ranging between 32 and 55 °F (0 and 13 °C) around 1970,[33] helps to moderate surrounding air temperatures in the summer (cooler with frequentsea breeze formations) and winter, and createslake-effect snow in colder months. The hills and mountains that border the lake hold moisture and fog, particularly in the fall.
The mountains steadily eroded, depositing layers ofsediments that compacted and becamelimestone,dolomite,taconite and theshale atKakabeka Falls. The continental crust was laterriven, creating one of the deepest rifts in the world.[35] The lake lies in this long-extinctMesoproterozoicrift valley, theMidcontinent Rift. Magma was injected between layers ofsedimentary rock, formingdiabasesills. This hard diabase protects the layers of sedimentary rock below, forming the flat-topped mesas in theThunder Bay area.Amethyst formed in some of the cavities created by the Midcontinent Rift, and there are several amethyst mines in the Thunder Bay area.[36]
Lava erupted from the rift and formed the black basalt rock of Michipicoten Island, Black Bay Peninsula, andSt. Ignace Island.[citation needed]
In the most recent geological history, during theWisconsin glaciation 10,000 years ago, ice covered the region at a thickness of 1.25 miles (2 km). The land contours familiar today were carved by the advance and retreat of theice sheet. The retreat left gravel, sand, clay and boulder deposits. Glacial meltwaters gathered in the Superior basin creatingLake Minong, a precursor to Lake Superior.[37] Without the immense weight of the ice, the landrebounded, and a drainage outlet formed at Sault Ste. Marie, becoming today's St. Mary's River.
Historical map of Lake Superior and Northern Michigan, published 1879 by Rand McNally
The first people came to the Lake Superior region 10,000 years ago after the retreat of the glaciers in theLast Glacial Period. They are known as thePlano, and they used stone-tipped spears to huntcaribou on the northwestern side of Lake Minong. The ShieldArchaic peoples arrived around 5000 BC; evidence of this culture can be 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 established trading networks. They are believed to be the direct ancestors of the Ojibwe andCree.[38] The people of theLaurel complex (c. 500 BC to AD 500) developedseine net fishing, evidence being found at rivers around Superior such as the Pic and Michipicoten. The people of the TerminalWoodland period were evident in the area from AD 900 to 1650. They wereAlgonquian peoples who hunted, fished and gathered berries. They usedsnowshoes,birch bark canoes and conical or domed lodges. At the mouth of the Michipicoten River, nine layers of encampments have been discovered. Most of thePukaskwa Pits were likely made during this time.[38]
TheAnishinaabe people (an ethnic grouping including theOjibwe/Chippewa) have inhabited the Lake Superior region for over five hundred years and were preceded by theDakota,Meskwaki (Fox),Menominee, Nipigon,Noquet andGros Ventres. After the arrival of Europeans, the Anishinaabe made themselves middle-men between the Frenchfur traders and other Native peoples. They soon became the dominant Native American nation in the region: they forced out theSioux and Fox and won a victory against theIroquois west of Sault Ste. Marie in 1662. By the mid-18th century, the Ojibwe occupied all of Lake Superior's shores.[39]
In the 18th century, as the booming fur trade supplied Europe withbeaver hats, theHudson's Bay Company had a virtual monopoly in the region until 1783, when the rivalNorth West Company was formed. The North West Company built forts on Lake Superior atGrand Portage,Fort William, Nipigon, the Pic River, the Michipicoten River, and Sault Ste. Marie. But by 1821, with competition harming the profits of both, the companies merged under the Hudson's Bay Company name. Many towns around the lake are current or former mining areas, or engaged in processing or shipping. Today, tourism is another significant industry: the sparsely populated Lake Superior country, with its rugged shorelines and wilderness, attracts vacationers and adventurers.
"Ice blockade in Marquette Harbor, June 1873", stereoscopic photo
Lake Superior has been an important link in theGreat Lakes Waterway, providing a route for the transportation of iron ore as well as grain and other mined and manufactured materials. Large cargo vessels called lake freighters, as well as smaller ocean-goingfreighters, transport these commodities across Lake Superior. Shipping was slow to arrive at Lake Superior in the 19th century. The first steamboat to run on the lake was theIndependence in 1847, whereas the first steamers on the other Great Lakes began sailing in 1816.[40][41] Ice closes the lake shipping from mid-January to late March. Exact dates for the shipping season vary each year,[42] depending on weather conditions that form and break the ice.
Wreckage ofSS Cyprus—a 420-foot (130 m) ore carrier that sank on October 11, 1907, during a Lake Superior storm in 77 fathoms (460 ft; 140 m) of water—was located in August 2007. Built inLorain, Ohio,Cyprus was launched August 17, 1907, and was lost on her second voyage hauling iron ore from Superior, Wisconsin, to Buffalo, New York, with the sole survivor among her 23 crew being Charles G. Pitz.[44] In 1918 the last warships to sink in the Great Lakes,French minesweepersInkerman andCerisoles, vanished in a Lake Superior storm, perhaps upon striking the uncharted danger of theSuperior Shoal in an otherwise deep part of the lake. With 78 crewmembers dead, their sinking marked the largest loss of life on Lake Superior to date.
SS Edmund Fitzgerald is the last ship that sank in Lake Superior, 15nautical miles (28 km; 17 mi) from Whitefish Point in a storm on November 10, 1975. The wreck was immortalized byGordon Lightfoot in his ballad"The Wreck of theEdmund Fitzgerald". All 29 crew members died, and no bodies were recovered.Edmund Fitzgerald was battered so intensely by Lake Superior that the 729-foot (222 m) ship split in half; her two pieces lie approximately 170 feet (52 m) apart at a depth of 88 fathoms (530 ft; 160 m).
Lightfoot sings that "Superior, they said, never gives up her dead".[45] This is because of the unusually cold water, under 36 °F (2 °C) on average around 1970.[33] Normally, bacteria decaying a sunken body will bloat it with gas, causing it to float to the surface after a few days. But Lake Superior's water is cold enough year-round to inhibitbacterial growth, and bodies tend to sink and never resurface.[46]Joe MacInnis reported that in July 1994, explorer Frederick Shannon's Expedition 94 to the wreck ofEdmund Fitzgerald discovered a man's body near the port side of her pilothouse, not far from the open door, "fully clothed, wearing an orange life jacket, and lying face down in the sediment".[47]
In February 2024, it was announced that wreckage from theSSArlington, which sank in 1940, was discovered.[48]
Lake Superior has fewer dissolved nutrients relative to its water volume than the other Great Lakes and so is less productive in terms of fish populations and is anoligotrophic lake. This is a result of the underdeveloped soils found in its relatively small watershed.[19] It is also a reflection of relatively small human population and small amount of agriculture in its watershed. However,nitrate concentrations in the lake have been continuously rising for more than a century. They are still much lower than levels considered dangerous to human health; but this steady, long-term rise is an unusual record of environmental nitrogen buildup. It may relate to anthropogenic alternations to the regionalnitrogen cycle, but researchers are still unsure of the causes of this change to the lake's ecology.[51]
As for other Great Lakes fish, populations have also been affected by the accidental or intentional introduction of foreign species such as the sea lamprey andEurasian ruffe. Accidental introductions have occurred in part by the removal of natural barriers to navigation between the Great Lakes. Overfishing has also been a factor in the decline of fish populations.[12]
^TheCaspian Sea is the largest lake, but is saline, not freshwater.Lake Michigan–Huron has a larger combined surface area than Superior, but is normally considered two separate lakes.
^North America (2.47×107 km2) andSouth America (1.78×107 km2) combined cover 4.26×107 km2. Lake Superior's volume (1.20×104 km3) over 4.26×107 km2 gives a depth of 0.282 m.
^abNational Geophysical Data Center (1999)."Bathymetry of Lake Superior". National Oceanic and Atmospheric Administration. RetrievedMarch 23, 2015. (the general reference to NGDC because this lake was never published, compilation of Great Lakes Bathymetry at NGDC has been suspended).
^National Geophysical Data Center (1999)."Bathymetry of Lake Huron". National Oceanic and Atmospheric Administration.doi:10.7289/V5G15XS5. RetrievedMarch 23, 2015.{{cite journal}}:Cite journal requires|journal= (help) (only small portion of this map)
^abGreat Lakes Environmental Research Laboratory."About Our Great Lakes: Tour". National Oceanic and Atmospheric Administration. Archived fromthe original on May 7, 2017. RetrievedDecember 15, 2017.
^"Great Lakes Water Levels"(PDF). United States Army Corps of Engineers. Archived fromthe original(PDF) on April 18, 2013. RetrievedJune 27, 2013. The link also has daily elevations for the current month.
^Chisholm, Barbara & Gutsche, Andrea (1998).Under the Shadow of the Gods: A Guide to the History of the Canadian Shore of Lake Superior (1st ed.). Transcontinental Printing.
^"Great Lakes Atlas". Environment Canada and United States Environmental Protection Agency. 1995. Archived fromthe original on August 2, 2012.
^*Bowen, Dana Thomas (1953).Great Lakes Ships and Shipping(PDF). Minnesota Historical Society. p. 9. Archived fromthe original(PDF) on July 14, 2020. RetrievedOctober 28, 2019.
^"Paul R. Treggurtha: Last Trip for theTregurtha This Year".Duluth Shipping News. January 12, 2015. Archived fromthe original on May 20, 2020. RetrievedJanuary 21, 2015.Another trip here was planned but has apparently been canceled, making this her last and 41st visit this season. Last year, without a late start due to ice, the Tregurtha was here 49 times.
^Stonehouse, Frederick (1998) [1985].Lake Superior's Shipwreck Coast. Gwinn, Michigan: Avery Color Studios. p. 267.ISBN0-932212-43-3.
Holdon, Thom (July–August 1977). "Reef of the Three C's".The Nor'easter. Vol. 2, no. 4. Duluth, MN: Lake Superior Marine Museum.
——— (May–August 1978). "Above and Below: Steamer America".The Nor'easter. Vol. 3, no. 3 & 4. Duluth, Minnesota: Lake Superior Marine Museum.
Hyde, Charles K.; Mahan, Ann & Mahan, John (1995).The Northern Lights: Lighthouses of the Upper Great Lakes. Detroit: Wayne State University Press.ISBN9780814325544.
Langston, Nancy (2017).Sustaining Lake Superior: An Extraordinary Lake in a Changing World. New Haven, Connecticut: Yale University Press.
Oleszewski, Wes (1998).Great Lakes Lighthouses, American and Canadian: A Comprehensive Directory/Guide to Great Lakes Lighthouses. Gwinn, Michigan: Avery Color Studios.ISBN0-932212-98-0.
Penrod, John (1998).Lighthouses of Michigan. Berrien Center, Michigan: Penrod/Hiawatha.ISBN978-0-942618-78-5.
Sims, P.K. & Carter, L.M.H., eds. (1996).Archean and Proterozoic Geology of the Lake Superior Region, U.S.A., 1993. Washington, DC: United States Geological Survey. Professional Paper 1556.
Splake, T. Kilgore (1984).Superior Land Lights. Battle Creek, Michigan: Angst Productions.
"S.S. George M. Cox Wrecked".The Daily Mining Gazette. Houghton, Michigan. May 28, 1933.
Stonehouse, Frederick (1974).Marquette Shipwrecks. Marquette, Michigan: Harboridge Press.
——— (1977).Isle Royale Shipwrecks. Marquette, Michigan: Avery Color Studios.
United States Army Corps of Engineers (August 2007). "[Record Low Water Levels Expected on Lake Superior]".
Wagner, John L. (1998).Michigan Lighthouses: An Aerial Photographic Perspective. East Lansing, Michigan: John L. Wagner.ISBN9781880311011.
"Wreck of Sidewheel Steamer Cumberland".Detroit Free Press. January 29, 1974.
Wright, Larry & Wright, Patricia (2006).Great Lakes Lighthouses Encyclopedia. Erin: Boston Mills Press.ISBN1-55046-399-3.
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