Lake Superior

For the the Quebec municipality, see Lac-Supérieur.

Lake Superior
Coordinates	47.7°N 87.5°W / 47.7; -87.5
Type	rift lake
Primary inflows	Nipigon River, St. Louis River Pigeon River Pic River White River Michipicoten River Kaministiquia River
Primary outflows	St. Marys River
Basin countries	Canada, USA
Max. length	563 km (350 mi)
Max. width	257 km (160 mi)
Surface area	82,414 km² (31,820 mi²) Canadian portion 28,700 km² (11,080 mi²)
Average depth	147 m (482 ft)
Max. depth	406 m (1333 ft)
Water volume	12,100 km³ (2900 mi³)
Residence time	191 years
Shore length1	4385 km (2725 mi)
Surface elevation	183 m (600 ft)
Islands	Isle Royale Apostle Islands
Settlements	Duluth, Minnesota Superior, Wisconsin Thunder Bay, Ontario Marquette, Michigan Sault Ste. Marie, Michigan Sault Ste. Marie, Ontario
1 Shore length is not a well-defined measure.

Lake Superior, bounded by Ontario, Canada and Minnesota, USA, to the north and Wisconsin and Michigan, USA, to the south, is the largest of North America's Great Lakes. It is the largest freshwater lake in the world by surface area and is the world's fourth-largest freshwater lake by volume.

Name

In the Ojibwe language, the lake is called "Gichigami" ("big water"), but it is better known as "Gitche Gumee" as recorded by Henry Wadsworth Longfellow in The Song of Hiawatha. Lake Superior is referred to as "Gitche Gumee" in the song The Wreck of the Edmund Fitzgerald, by Gordon Lightfoot.

The lake was named le lac supérieur, or "Upper Lake," in the seventeenth century by French explorers because it was located above Lake Huron.(Nute, 1946)

Hydrography

Lake Superior and the other Great Lakes

File:LakeSuperior arf.JPG

Lake Superior in winter, as seen from Duluth in December 2004

Lake Superior is the largest freshwater lake in the world by surface area. Lake Baikal in Russia is larger by volume, as is Lake Tanganyika (The Caspian Sea, while vastly larger than Lake Superior in both surface area and volume, is saline; though presently isolated, in the past, it has been repeatedly connected to, and isolated from, the Mediterranean via the Black Sea).

Lake Superior (47.7° N, 87.5° W) has a surface area of 31,820 square miles (82,414 km²)—which is larger than South Carolina. It has a maximum length of 350 miles (563 km) and maximum breadth of 160 miles (257 km). Its average depth is 483 feet (147 m) with a maximum depth of 1,333 feet (406 m). Lake Superior contains 2,900 cu mi (12,100 km³) of water. There is enough water in Lake Superior to cover the entire land mass of North and South America with a foot (30 cm) of water. The shoreline of the lake stretches 2,726 miles (4,385 km) (including islands). The lake's elevation is 600 feet (183 m) above sea level. American limnologist J. Val Klump was the first person to reach the lowest depth of Lake Superior on July 30, 1985 as part of a scientific expedition.

Annual storms on Lake Superior regularly record wave heights of over 20 feet (6 m). Waves well over 30 feet (9 m) have been recorded.

Water levels, including diversions of water from the Hudson Bay watershed, are governed by the International Lake Superior Board of Control which was established in 1914 by the International Joint Commission.

Tributaries and outlet

The lake is fed by over 200 rivers. The largest include the Nipigon River, the St. Louis River, the Pigeon River, the Pic River, the White River, the Michipicoten River, the Brule River and the Kaministiquia River. Lake Superior drains into Lake Huron by the St. Marys River. The rapids on the river necessitate the Sault Locks (pronounced "soo"), a part of the Great Lakes Waterway, to move boats over the 25 foot (7.6 m) height difference from Lake Huron.

Geography

The largest island in Lake Superior is Isle Royale in the state of Michigan. Other large famous islands include Madeline Island in the state of Wisconsin and Michipicoten in the province of Ontario.

The larger towns on Lake Superior include: the twin ports of Duluth, Minnesota and Superior, Wisconsin; Thunder Bay, Ontario; Marquette, Michigan; and the two cities of Sault Ste. Marie, in Michigan and in Ontario. Duluth, at the western tip of Lake Superior, is the most inland point on the Saint Lawrence Seaway and the most inland port in the world.

Among the scenic places on the lake are: the Apostle Islands National Lakeshore; Isle Royale National Park; Pukaskwa National Park; Lake Superior Provincial Park; Grand Island National Recreation Area; Sleeping Giant (Ontario);and Pictured Rocks National Lakeshore.

Climate

Lake Superior's size creates a localized oceanic or maritime climate (more typically seen in locations like Nova Scotia) . The water surface's slow reaction to temperature changes, seasonally ranging between 0-13°C around 1970, helps to moderate surrounding air temperatures in the summer and winter, and creates lake effect snow in colder months. The hills and mountains that border the lake form a bowl, which holds moisture and fog, particularly in the fall. The Lake Superior's surface temperature has warmed by 2.5°C since 1979, which is attributed to global warming.

Geology

North American cratons and basement rock, showing the formation of the Midcontinent Rift containing today's Lake Superior

Lake Superior's North Shore dates back to the beginnings of the earth. Ages ago, magma forcing its way to the surface created the intrusive granites of the Canadian Shield. These ancient granites can be seen on the North Shore today. It was in this period, the Penokean orogeny, that many valuable metals were deposited. The region surrounding the lake has proved to be rich in minerals. Copper, iron, silver, gold and nickel are or were the most frequently mined. Examples include the Hemlo gold mine near Marathon, copper at Point Mamainse, silver at Silver Islet, and uranium at Theano Point.

The mountains steadily eroded, depositing layers of sediments which compacted and became limestone, dolostone, taconite, and the shale at Kakabeka Falls.

The continent was later rifted, creating one of the deepest rifts in the world. The lake lies above this long-extinct Mesoproterozoic rift valley, the Midcontinent Rift, which explains its great depths. Magma was injected between layers of sedimentary rock, forming diabase sills. This hard diabase protects the layers of sedimentary rock below, forming the flat-topped mesas in the Thunder 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.

Lava erupted from the rift and formed the black basalt rock of Michipicoten Island, Black Bay Peninsula, and St. Ignace Island.

During the Great Ice Age, 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 the ice sheet. The retreat left gravel, sand, clay, and boulder deposits. Glacial meltwaters gathered in the Superior basin creating Lake Minong, a precursor to Lake Superior. Without the immense weight of the ice, the land rebounded, and a drainage outlet formed at Sault Ste. Marie, which would become known as St. Mary's River.

History

Pictographs at Lake Superior Provincial Park, Ontario

The first people came to the Lake Superior region 10,000 years ago after the retreat of the glaciers in the last Ice Age. They were known as the Plano, and they used stone-tipped spears to hunt caribou on the northwestern side of Lake Minong.

The next documented people were known as the Shield Archaic (c. 5000-500 B.C.). Evidence of this culture can be found at the eastern and western ends of the Canadian shore. They used bows and arrows, 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 and Cree.

The Laurel people (c. 500 B.C. to A.D. 500) developed seine net fishing, evidence being found at rivers around Superior such as the Pic and Michipicoten.

Another culture known as the Terminal Woodland Indians (c. A.D. 900-1650) has been found. They were Algonkian people who hunted, fished and gathered berries. They used snow shoes, birch bark canoes and conical or domed lodges. At the mouth of the Michipicoten River, nine layers of encampments have been discovered. Most of the Pukaskwa Pits were likely made during this time.

The Anishinabe, also known as the Ojibwe or Chippewa, have inhabited the Lake Superior region for over five hundred years, and were preceded by the Dakota, Fox, Menominee, Nipigon, Noquet, and Gros Ventres. They called Lake Superior Anishnaabe Chi Gaming, or "the Ojibwe's Ocean". After the arrival of Europeans, the Anishinabe made themselves the middle-men between the French fur traders and other Native peoples. They soon became the dominant Indian nation in the region: they forced out the Sioux and Fox and won a victory against the Iroquois west of Sault Ste. Marie in 1662. By the mid-1700s, the Ojibwe occupied all of Lake Superior's shores.

In the 1700s, the fur trade in the region was booming, with the Hudson's Bay Company (HBC) having a virtual monopoly. In 1783, however, the North West Company (NWC) was formed to rival HBC. The NWC built forts on Lake Superior at Grand Portage, Nipigon, the Pic River, the Michipicoten River, and Sault Ste. Marie. But by 1821, with competition taking too great a toll on both, the companies merged under the Hudson's Bay Company name.

Many towns around the lake are either current or former mining areas, or engaged in processing or shipping. Today, tourism is another significant industry as the sparsely populated Lake Superior country, with its rugged shorelines and wilderness, attracts tourists and adventurers.

Shipping

Lake Superior has been an important link in the Great Lakes Waterway, providing a route for the transportation of iron ore and other mined and manufactured materials. Large cargo vessels called lake freighters, as well as smaller ocean-going freighters, transport these commodities across Lake Superior.

File:Fitzgeraldpic.jpg

The SS Edmund Fitzgerald, a typical lake freighter which sank in 1975

Shipwrecks

The last major shipwreck on Lake Superior was that of SS Edmund Fitzgerald in 1975.

According to an old sailor's tale, Lake Superior never gives up her dead. This is because of the low temperature of the water, estimated at under 2°C on average around 1970. Normally bacteria feeding off a sunken decaying body will generate gas inside the body, causing it to float to the surface after a few days. The water in Lake Superior, however, is cold enough year-round to inhibit bacterial growth, meaning bodies tend to sink and never surface. This is poetically alluded to in Gordon Lightfoot's famous ballad, The Wreck of the Edmund Fitzgerald.

Cyprus

On August, 2007, Tom Farnquist (executive director, Great Lakes Shipwreck Historical Society) said, it found the wreckage (460 feet beneath the surface) of Cyprus, a 420-foot-long century-old ship ore carrier which sank during a Lake Superior storm. All but Charles G. Pitz of the Cyprus’ 23 crew perished on Oct. 11, 1907. The Ore carrier sank in Lake Superior on its second voyage, while hauling iron ore from Superior, Wisconsin, to Buffalo, N.Y. Built in Lorain, Ohio, the Cyprus was launched Aug. 17, 1907.

Ecology

Although part of a single system, each of the Great Lakes is different. In volume, Lake Superior is the largest. It is also the deepest and coldest of the five. Superior could contain all the other Great Lakes and three more Lake Eries. Because of its size, Superior has a retention time of 191 years.

Superior's water levels have been decreasing since the early 1990's and in September 2007, Lake Superior's water level set a new record low, dipping lower than the previous record set in 1926. --Weathermatrix 19:25, 6 October 2007 (UTC)

According to a study by professors at the University of Minnesota Duluth, Lake Superior has been warming faster than its surrounding climate. Summer surface temperatures in the lake have increased about 2.5°C since 1979, compared with about a 1.5°C increase in the surrounding average air temperature. The increase in the lake’s surface temperature is not only due to climate change but also due to the decreasing ice cover. Less winter ice cover allows more solar radiation to penetrate the lake and warm the water. If trends continue Lake Superior, which freezes over completely once every 20 years, could routinely be ice-free by 2040. These warmer temperatures can actually lead to more snow in the lake effect snow belts along the shores of the lake, especially in the Upper Peninsula of Michigan.

Over sixty species of fish have been found in Lake Superior, among them: bloater, brook trout, brown trout, burbot, carp, chinook salmon, coho salmon, freshwater drum, lake herring, lake sturgeon, lake trout, lake whitefish, longnose sucker, muskellunge, northern pike, pumpkinseed, pink salmon, rainbow smelt, rainbow trout, rock bass, round goby, round whitefish, ruffe, sea lamprey, smallmouth bass, walleye, white perch, white sucker, and yellow perch.

Lake Superior has less dissolved nutrients relative to its size compared to the other Great Lakes and so is less productive in terms of fish populations. This is a result of the underdeveloped soils found in its relatively small 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 envronmental N buildup. It might relate to anthropogenic alternations to the regional N cycle, but researchers are still unsure of the causes of this change to the lake's ecology. As for other Great Lakes, fish populations have also been impacted by the accidental or intentional introduction of foreign species such as the sea lamprey and eurasian ruffe. Accidental introductions have occurred in part due to the removal of natural barriers to navigation between the Great Lakes. Overfishing has also been a factor in the decline of fish populations.

See also

• the North Shore of Lake Superior
• the South Shore of Lake Superior
• Great Lakes Areas of Concern

External links

• International Lake Superior Board of Control
• EPA's Great Lakes Atlas
• EPA's Great Lakes Atlas Factsheet #1
• Parks Canada Lake Superior
• Minnesota Sea Grant - Lake Superior Page