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Great Lakes

Lakes in North America

Top 10 Great Lakes related articles

Coordinates: 45°N 84°W / 45°N 84°W / 45; -84

Satellite image of the Great Lakes, April 24, 2000
Terra MODIS image of the Great Lakes, January 27, 2005, showing ice beginning to build up around the shores of each of the lakes, with snow on the ground.
Location in North America

The Great Lakes or the Great Lakes of North America, are a series of interconnected freshwater lakes in the upper mid-east region of North America, that connect to the Atlantic Ocean through the Saint Lawrence River. In general, they are on or near the Canada–United States border. They are lakes Superior, Michigan, Huron, Erie, and Ontario. Hydrologically, there are only four lakes, because lakes Michigan and Huron join at the Straits of Mackinac. The lakes form the basis for Great Lakes Waterway.

The Great Lakes are the largest group of freshwater lakes on Earth by total area, and second-largest by total volume, containing 21% of the world's surface fresh water by volume.[1][2][3] The total surface is 94,250 square miles (244,106 km2), and the total volume (measured at the low water datum) is 5,439 cubic miles (22,671 km3),[4] slightly less than the volume of Lake Baikal (5,666 cu mi or 23,615 km3, 22–23% of the world's surface fresh water). Due to their sea-like characteristics (rolling waves, sustained winds, strong currents, great depths, and distant horizons) the five Great Lakes have also long been referred to as inland seas.[5] Lake Superior is the second-largest lake in the world by area, and the largest freshwater lake by surface area. Lake Michigan is the largest lake that is entirely within one country.[6][7][8][9]

The Great Lakes began to form at the end of the last glacial period around 14,000 years ago, as retreating ice sheets exposed the basins they had carved into the land which then filled with meltwater.[10] The lakes have been a major source for transportation, migration, trade, and fishing, serving as a habitat to many aquatic species in a region with much biodiversity.

The surrounding region is called the Great Lakes region, which includes the Great Lakes Megalopolis.[11]

Great Lakes Intro articles: 11

Geography

A map of the Great Lakes Basin showing the five sub-basins within. Left to right they are: Superior, including Nipigon's basin, (magenta); Michigan (blue); Huron (green); Erie (yellow); Ontario (orange).

Though the five lakes lie in separate basins, they form a single, naturally interconnected body of fresh water, within the Great Lakes Basin. As a chain of lakes and rivers they connect the east-central interior of North America to the Atlantic Ocean. From the interior to the outlet at the Saint Lawrence River, water flows from Superior to Huron and Michigan, southward to Erie, and finally northward to Lake Ontario. The lakes drain a large watershed via many rivers, and are studded with approximately 35,000 islands.[12] There are also several thousand smaller lakes, often called "inland lakes", within the basin.[13] The surface area of the five primary lakes combined is roughly equal to the size of the United Kingdom, while the surface area of the entire basin (the lakes and the land they drain) is about the size of the UK and France combined.[14] Lake Michigan is the only one of the Great Lakes that is entirely within the United States; the others form a water boundary between the United States and Canada. The lakes are divided among the jurisdictions of the Canadian province of Ontario and the U.S. states of Michigan, Wisconsin, Minnesota, Illinois, Indiana, Ohio, Pennsylvania, and New York. Both the province of Ontario and the state of Michigan include in their boundaries portions of four of the lakes: The province of Ontario does not border Lake Michigan, and the state of Michigan does not border Lake Ontario. New York and Wisconsin's jurisdictions extend into two lakes, and each of the remaining states into one of the lakes.

Bathymetry

Relative elevations, average depths, maximum depths, and volumes of the Great Lakes.
Notes: The area of each rectangle is proportionate to the volume of each lake. All measurements at Low Water Datum.
Source: EPA[15]
Lake Erie Lake Huron Lake Michigan Lake Ontario Lake Superior
Surface area[4] 9,910 sq mi (25,700 km2) 23,000 sq mi (60,000 km2) 22,300 sq mi (58,000 km2) 7,340 sq mi (19,000 km2) 31,700 sq mi (82,000 km2)
Water volume[4] 116 cu mi (480 km3) 850 cu mi (3,500 km3) 1,180 cu mi (4,900 km3) 393 cu mi (1,640 km3) 2,900 cu mi (12,000 km3)
Elevation[15] 571 ft (174 m) 577 ft (176 m) 577 ft (176 m) 246 ft (75 m) 600.0 ft (182.9 m)
Average depth[14] 62 ft (19 m) 195 ft (59 m) 279 ft (85 m) 283 ft (86 m) 483 ft (147 m)
Maximum depth[16] 210 ft (64 m) 748 ft (228 m) 925 ft (282 m) 804 ft (245 m) 1,333 ft (406 m)
Major settlements[17] Buffalo, NY
Erie, PA
Cleveland, OH
Lorain, OH
Toledo, OH
Sandusky, OH
Alpena, MI
Bay City, MI
Owen Sound, ON
Port Huron, MI
Sarnia, ON
Chicago, IL
Gary, IN
Green Bay, WI
Sheboygan, WI
Milwaukee, WI
Kenosha, WI
Racine, WI
Muskegon, MI
Traverse City, MI
Hamilton, ON
Kingston, ON
Mississauga, ON
Oshawa, ON
Rochester, NY
Toronto, ON
Duluth, MN
Marquette, MI
Sault Ste. Marie, MI
Sault Ste. Marie, ON
Superior, WI
Thunder Bay, ON
System profile of the Great Lakes.

As the surfaces of Lakes Superior, Huron, Michigan, and Erie are all approximately the same elevation above sea level, while Lake Ontario is significantly lower, and because the Niagara Escarpment precludes all natural navigation, the four upper lakes are commonly called the "upper great lakes". This designation is not universal. Those living on the shore of Lake Superior often refer to all the other lakes as "the lower lakes", because they are farther south. Sailors of bulk freighters transferring cargoes from Lake Superior and northern Lake Michigan and Lake Huron to ports on Lake Erie or Ontario commonly refer to the latter as the lower lakes and Lakes Michigan, Huron, and Superior as the upper lakes. This corresponds to thinking of lakes Erie and Ontario as "down south" and the others as "up north". Vessels sailing north on Lake Michigan are considered "upbound" even though they are sailing toward its effluent current.[24]

Primary connecting waterways

Chicago on Lake Michigan is in the western part of the lakes megalopolis, and the site of the waterway linking the lakes to the Mississippi River valley
Detroit on the Detroit River links the region's central metropolitan areas.
Toronto on Lake Ontario is in the eastern section of the Great Lakes Megalopolis

Lake Michigan–Huron

Lakes Huron and Michigan are sometimes considered a single lake, called Lake Michigan–Huron, because they are one hydrological body of water connected by the Straits of Mackinac.[25] The straits are five miles (8 km) wide[14] and 120 feet (37 m) deep; the water levels rise and fall together,[26] and the flow between Michigan and Huron frequently reverses direction.

Large bays and related significant bodies of water

Islands

South Bass Island in Lake Erie

Dispersed throughout the Great Lakes are approximately 35,000 islands.[12] The largest among them is Manitoulin Island in Lake Huron, the largest island in any inland body of water in the world.[34] The second-largest island is Isle Royale in Lake Superior.[35] Both of these islands are large enough to contain multiple lakes themselves—for instance, Manitoulin Island's Lake Manitou is the world's largest lake on a freshwater island.[36] Some of these lakes even have their own islands, like Treasure Island in Lake Mindemoya in Manitoulin Island

Peninsulas

The Great Lakes also have several peninsulas between them, including the Door Peninsula, the Peninsulas of Michigan, and the Ontario Peninsula. Some of these peninsulas even contain smaller peninsulas, such as the Keweenaw Peninsula, the Thumb Peninsula, the Bruce Peninsula, and the Niagara Peninsula. Population centers on the peninsulas include Grand Rapids and Detroit in Michigan along with London, Hamilton, Brantford, and Toronto in Ontario.

Shipping connection to the ocean

Although the Saint Lawrence Seaway and Great Lakes Waterway make the Great Lakes accessible to ocean-going vessels,[37] shifts in shipping to wider ocean-going container ships—which do not fit through the locks on these routes—have limited container shipping on the lakes. Most Great Lakes trade is of bulk material, and bulk freighters of Seawaymax-size or less can move throughout the entire lakes and out to the Atlantic.[38] Larger ships are confined to working in the lakes themselves. Only barges can access the Illinois Waterway system providing access to the Gulf of Mexico via the Mississippi River. Despite their vast size, large sections of the Great Lakes freeze over in winter, interrupting most shipping from January to March. Some icebreakers ply the lakes, keeping the shipping lanes open through other periods of ice on the lakes.

The Great Lakes are also connected by the Chicago Sanitary and Ship Canal to the Gulf of Mexico by way of the Illinois River (from the Chicago River) and the Mississippi River. An alternate track is via the Illinois River (from Chicago), to the Mississippi, up the Ohio, and then through the Tennessee–Tombigbee Waterway (a combination of a series of rivers and lakes and canals), to Mobile Bay and the Gulf of Mexico. Commercial tug-and-barge traffic on these waterways is heavy.[39]

Pleasure boats can also enter or exit the Great Lakes by way of the Erie Canal and Hudson River in New York. The Erie Canal connects to the Great Lakes at the east end of Lake Erie (at Buffalo, New York) and at the south side of Lake Ontario (at Oswego, New York).

Water levels

In 2009, the lakes contained 84% of the surface freshwater of North America;[40] if the water were evenly distributed over the entire continent's land area, it would reach a depth of 5 feet (1.5 meters).[14] The source of water levels in the lakes is tied to what was left by melting glaciers when the lakes took their present form. Annually, only about 1% is "new" water originating from rivers, precipitation, and groundwater springs that drain into the lakes. Historically, evaporation has been balanced by drainage, making the level of the lakes constant.[14]

Intensive human population growth only began in the region in the 20th century and continues today.[14] At least two human water use activities have been identified as having the potential to affect the lakes' levels: diversion (the transfer of water to other watersheds) and consumption (substantially done today by the use of lake water to power and cool electric generation plants, resulting in evaporation).[41]

The physical impacts of climate change can be seen in water levels in the Great Lakes over the past century.[42] The United Nations' Intergovernmental Panel on Climate Change in 1997 predicted: "the following lake level declines could occur: Lake Superior −0.2 to −0.5 m, Lakes Michigan and Huron −1.0 to −2.5 m, and Lake Erie −0.9 to −1.9 m."[43] In 2009, it was predicted that global warming will decrease water levels.[44] In 2013, record low water levels in the Great Lakes were attributed to climate change.[45]

Water levels of Lakes Michigan and Huron in the United States, 1918 to 2019.

The water level of Lake Michigan–Huron had remained fairly constant over the 20th century,[46] but has nevertheless dropped more than 6 feet from the record high in 1986 to the low of 2013.[47] In 2012, National Geographic tied the water level drop to warming climate change.,[48] as did the Natural Resources Defense Council.[49] One newspaper reported that the long-term average level has gone down about 20 inches because of dredging and subsequent erosion in the St. Clair River. Lake Michigan–Huron hit all-time record low levels in 2013; according to the US Army Corps of Engineers, the previous record low had been set in 1964.[47] By April 2015 the water level had recovered to 7 inches (17.5 cm) more than the "long term monthly average".[50]

Great Lakes Geography articles: 142

Name origins

The Great Lakes during early spring
Lake Erie
From the Erie tribe, a shortened form of the Iroquoian word erielhonan "long tail".[51]
Lake Huron
Named for the inhabitants of the area, the Wyandot (or "Hurons"), by the first French explorers .[52] The Wyandot originally referred to the lake by the name karegnondi, a word which has been variously translated as "Freshwater Sea", "Lake of the Hurons", or simply "lake".[53][54]
Lake Michigan
From the Ojibwa word mishi-gami "great water" or "large lake".[55]
Lake Ontario
From the Wyandot (Huron) word ontarí'io "lake of shining waters".[56]
Lake Superior
English translation of the French term lac supérieur "upper lake", referring to its position north of Lake Huron. The indigenous Ojibwe call it gichi-gami (from Ojibwe gichi "big, large, great"; gami "water, lake, sea"). Popularized in French-influenced transliteration as Gitchigumi as in Gordon Lightfoot's 1976 story song "The Wreck of the Edmund Fitzgerald", or Gitchee Gumee as in Henry Wadsworth Longfellow's 1855 epic poem, The Song of Hiawatha).[16]

Statistics

The Great Lakes contain 21% of the world's surface fresh water: 5,472 cubic miles (22,810 km3), or 6.0×1015 U.S. gallons, that is 6 quadrillion U.S gallons, (2.3×1016 liters). This is enough water to cover the 48 contiguous U.S. states to a uniform depth of 9.5 feet (2.9 m). Although the lakes contain a large percentage of the world's fresh water, the Great Lakes supply only a small portion of U.S. drinking water on a national basis.[57]

The total surface area of the lakes is approximately 94,250 square miles (244,100 km2)—nearly the same size as the United Kingdom, and larger than the U.S. states of New York, New Jersey, Connecticut, Rhode Island, Massachusetts, Vermont, and New Hampshire combined.[58]

The Great Lakes coast measures approximately 10,500 miles (16,900 km);,[14] but the length of a coastline is impossible to measure exactly and is not a well-defined measure (see Coastline paradox). Of the total 10,500 miles (16,900 km) of shoreline, Canada borders approximately 5,200 miles (8,400 km), while the remaining 5,300 miles (8,500 km) are bordered by the United States. Michigan has the longest shoreline of the United States, bordering roughly 3,288 miles (5,292 km) of shoreline, followed by Wisconsin (820 miles (1,320 km)), New York (473 miles (761 km)), and Ohio (312 miles (502 km)).[59] Traversing the shoreline of all the lakes would cover a distance roughly equivalent to travelling half-way around the world at the equator.[14]

Great Lakes Name origins articles: 10

Geology

A diagram of the formation of the Great Lakes
Map of Glacial Lake Algonquin and its Correlatives (USGS 1915)

It has been estimated that the foundational geology that created the conditions shaping the present day upper Great Lakes was laid from 1.1 to 1.2 billion years ago,[14][60] when two previously fused tectonic plates split apart and created the Midcontinent Rift, which crossed the Great Lakes Tectonic Zone. A valley was formed providing a basin that eventually became modern day Lake Superior. When a second fault line, the Saint Lawrence rift, formed approximately 570 million years ago,[14] the basis for Lakes Ontario and Erie were created, along with what would become the Saint Lawrence River.

The Great Lakes are estimated to have been formed at the end of the last glacial period (the Wisconsin glaciation ended 10,000 to 12,000 years ago), when the Laurentide Ice Sheet receded.[10] The retreat of the ice sheet left behind a large amount of meltwater (see Lake Algonquin, Lake Chicago, Glacial Lake Iroquois, and Champlain Sea) that filled up the basins that the glaciers had carved, thus creating the Great Lakes as we know them today.[61] Because of the uneven nature of glacier erosion, some higher hills became Great Lakes islands. The Niagara Escarpment follows the contour of the Great Lakes between New York and Wisconsin. Land below the glaciers "rebounded" as it was uncovered.[62] Since the glaciers covered some areas longer than others, this glacial rebound occurred at different rates.

A notable modern phenomenon is the formation of ice volcanoes over the lakes during wintertime. Storm-generated waves carve the lakes' ice sheet and create conical mounds through the eruption of water and slush. The process is only well-documented in the Great Lakes, and has been credited with sparing the southern shorelines from worse rocky erosion.[63]

Great Lakes Geology articles: 13

Climate

The Great Lakes have a humid continental climate, Köppen climate classification Dfa (in southern areas) and Dfb (in northern parts)[64] with varying influences from air masses from other regions including dry, cold Arctic systems, mild Pacific air masses from the West, and warm, wet tropical systems from the south and the Gulf of Mexico.[65] The lakes themselves also have a moderating effect on the climate; they can also increase precipitation totals and produce lake effect snowfall.[64]

Lake effect

The location of common lake effect bands on the Great Lakes

The Great Lakes can have an effect on regional weather called lake-effect snow, which is sometimes very localized. Even late in winter, the lakes often have no icepack in the middle. The prevailing winds from the west pick up the air and moisture from the lake surface, which is slightly warmer in relation to the cold surface winds above. As the slightly warmer, moist air passes over the colder land surface, the moisture often produces concentrated, heavy snowfall that sets up in bands or "streamers". This is similar to the effect of warmer air dropping snow as it passes over mountain ranges. During freezing weather with high winds, the "snow belts" receive regular snow fall from this localized weather pattern, especially along the eastern shores of the lakes. Snow belts are found in Wisconsin, Michigan, Ohio, Pennsylvania, and New York, United States; and Ontario, Canada.

The lakes also moderate seasonal temperatures to some degree, but not with as large an influence as do large oceans; they absorb heat and cool the air in summer, then slowly radiate that heat in autumn. They protect against frost during transitional weather, and keep the summertime temperatures cooler than further inland. This effect can be very localized and overridden by offshore wind patterns. This temperature buffering produces areas known as "Fruit Belts", where fruit can be produced that is typically grown much farther south. For instance, Western Michigan has apple and cherry orchards, and vineyards cultivated adjacent to the lake shore as far north as the Grand Traverse Bay and Nottawasaga Bay in central Ontario. The eastern shore of Lake Michigan and the southern shore of Lake Erie have many successful wineries because of the moderating effect, as does the Niagara Peninsula between Lake Erie and Lake Ontario. A similar phenomenon allows wineries to flourish in the Finger Lakes region of New York, as well as in Prince Edward County, Ontario on Lake Ontario's northeast shore. Related to the lake effect is the regular occurrence of fog over medium-sized areas, particularly along the shorelines of the lakes. This is most noticeable along Lake Superior's shores.

The Great Lakes have been observed to help intensify storms, such as Hurricane Hazel in 1954, and the 2011 Goderich, Ontario tornado, which moved onshore as a tornadic waterspout. In 1996 a rare tropical or subtropical storm was observed forming in Lake Huron, dubbed the 1996 Lake Huron cyclone. Rather large severe thunderstorms covering wide areas are well known in the Great Lakes during mid-summer; these Mesoscale convective complexes or MCCs[66] can cause damage to wide swaths of forest and shatter glass in city buildings. These storms mainly occur during the night, and the systems sometimes have small embedded tornadoes, but more often straight-line winds accompanied by intense lightning.

Great Lakes Climate articles: 14

Ecology

Generalized schematic of Great Lakes waterline ecosystem

Historically, the Great Lakes, in addition to their lake ecology, were surrounded by various forest ecoregions (except in a relatively small area of southeast Lake Michigan where savanna or prairie occasionally intruded). Logging, urbanization, and agriculture uses have changed that relationship. In the early 21st century, Lake Superior's shores are 91% forested, Lake Huron 68%, Lake Ontario 49%, Lake Michigan 41%, and Lake Erie, where logging and urbanization has been most extensive, 21%. Some of these forests are second or third growth (i.e. they have been logged before, changing their composition). At least 13 wildlife species are documented as becoming extinct since the arrival of Europeans, and many more are threatened or endangered.[14] Meanwhile, exotic and invasive species have also been introduced.

Fauna

Lake sturgeon, the largest native fish in the Great Lakes and the subject of extensive commercial fishing in the 19th and 20th centuries is listed as a threatened species[67]

While the organisms living on the bottom of shallow waters are similar to those found in smaller lakes, the deep waters contain organisms found only in deep, cold lakes of the northern latitudes. These include the delicate opossum shrimp (order mysida), the deepwater scud (a crustacean of the order amphipoda), two types of copepods, and the deepwater sculpin (a spiny, large-headed fish).[68]

The Great Lakes are an important source of fishing. Early European settlers were astounded by both the variety and quantity of fish; there were 150 different species in the Great Lakes.[14] Throughout history, fish populations were the early indicator of the condition of the Lakes and have remained one of the key indicators even in the current era of sophisticated analyses and measuring instruments. According to the bi-national (U.S. and Canadian) resource book, The Great Lakes: An Environmental Atlas and Resource Book: "The largest Great Lakes fish harvests were recorded in 1889 and 1899 at some 67,000 tonnes (66,000 long tons; 74,000 short tons) [147 million pounds]."[69]

By 1801, the New York Legislature found it necessary to pass regulations curtailing obstructions to the natural migrations of Atlantic salmon from Lake Erie into their spawning channels. In the early 19th century, the government of Upper Canada found it necessary to introduce similar legislation prohibiting the use of weirs and nets at the mouths of Lake Ontario's tributaries. Other protective legislation was passed, as well, but enforcement remained difficult.[70]

On both sides of the Canada–United States border, the proliferation of dams and impoundments have multiplied, necessitating more regulatory efforts. Concerns by the mid-19th century included obstructions in the rivers which prevented salmon and lake sturgeon from reaching their spawning grounds. The Wisconsin Fisheries Commission noted a reduction of roughly 25% in general fish harvests by 1875. The states have removed dams from rivers where necessary.[71]

Overfishing has been cited as a possible reason for a decrease in population of various whitefish, important because of their culinary desirability and, hence, economic consequence. Moreover, between 1879 and 1899, reported whitefish harvests declined from some 24.3 million pounds (11 million kg) to just over 9 million pounds (4 million kg).[72] By 1900, commercial fishermen on Lake Michigan were hauling in an average of 41 million pounds of fish annually.[73] By 1938, Wisconsin's commercial fishing operations were motorized and mechanized, generating jobs for more than 2,000 workers, and hauling 14 million pounds per year.[73] The population of giant freshwater mussels was eliminated as the mussels were harvested for use as buttons by early Great Lakes entrepreneurs.[72] Since 2000, the invasive quagga mussel has smothered the bottom of Lake Michigan almost from shore to shore, and their numbers are estimated at 900 trillion.[73]

The influx of parasitic lamprey populations after the development of the Erie Canal and the much later Welland Canal led to the two federal governments of the US and Canada working on joint proposals to control it. By the mid-1950s, the lake trout populations of Lakes Michigan and Huron were reduced, with the lamprey deemed largely to blame. This led to the launch of the bi-national Great Lakes Fishery Commission.

Cliffs at Palisade Head on Lake Superior in Minnesota near Silver Bay.

The Great Lakes: An Environmental Atlas and Resource Book (1972) noted: "Only pockets remain of the once large commercial fishery."[69] But, water quality improvements realized during the 1970s and 1980s, combined with successful salmonid stocking programs, have enabled the growth of a large recreational fishery.[74] The last commercial fisherman left Milwaukee in 2011 because of overfishing and anthropogenic changes to the biosphere.[73]

Since the 19th century an estimated 160 new species have found their way into the Great Lakes ecosystem; many have become invasive; the overseas ship ballast and ship hull parasitism are causing severe economic and ecological impacts.[75][76] According to the Inland Seas Education Association, on average a new species enters the Great Lakes every eight months.[76]

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