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Great Lakes

Great Lakes

Located in north-central North America, the Great Lakes are five large fresh-water lakes interconnected by natural and artificial waterways: Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario. Carved by ancient glaciers, these lakes contain approximately 20 percent of the world's surface fresh-water supply and 95 percent of the surface fresh water in the United States. The Great Lakes waterbody is so large that its natural features can be seen from the Moon.

Great Lakes Watershed

Native Americans were the original inhabitants of the Great Lakes basin. Historically, the Great Lakes played a significant role in Native American societies and approximately 120 bands of native peoples have occupied this region over the course of history. Notable tribes inhabiting the Great Lakes region include the Chippewa, Fox, Huron, Iroquois, Ottawa, Potawatomi, and Sioux. These Native peoples played an instrumental role when European explorers came to the region in the early 1600s, particularly in the development of the fur trade. Each of the names of the Great Lakes comes from either a Native tribe name or the Native words for the lakes.

Straddling the U.S.Canada boundary, today's Great Lakes watershed is home to approximately 40 million Americans and Canadians. This population represents about 10 percent of the U.S. population and 25 percent of the Canadian population. In the United States, four of the twelve largest cities are located on the shores of the Great Lakes. The lakes constitute the largest inland water transportation system in the world, and have played an important role in the economic development of both the United States and Canada.

The Lakes.

The Great Lakes encompass 16,000 kilometers (10,000 miles) of inland coastal waters, and collectively have been referred to as "the inland seas" and "the fourth coast of the United States". Lake Michigan is located entirely within the United States, while the other four lakes form a partial border between the United States and Canada. The lakes are bordered by the Canadian province of Ontario and by the eight U.S. states of Minnesota, Wisconsin, Illinois, Michigan, Indiana, Ohio, Pennsylvania, and New York. The westernmost point of the Great Lakes is near Duluth, Minnesota, and the easternmost point is just north of Syracuse, New York (and connects with the St. Lawrence Seaway).

Covering a total surface area of about 244,000 square kilometers (94,000 square miles) the Great Lakes contain a volume of approximately 23,000 cubic kilometers (5,500 cubic miles) of water. This tremendous volume is hard to conceptualize, but if it were spread over the contiguous 48 states, its waters would average about 2.9 meters (9.5 feet) deep. Together the lakes drain about 750,000 square kilometers (about 290,000 square miles), with the primary outlet being the St. Lawrence River.

The shores of the Great Lakes vary considerably from region to region. On the eastern side of Lake Michigan, sandy beaches are prevalent, whereas the shores of Lakes Superior and Huron are primarily rocky, and often framed by cliffs comprised of sandstone and shale. Wetlands are found along Lake Ontario's shore, including Canada's well-known Point Pelee National Park. These shoreline systems serve to protect their inland areas by absorbing the force of wind and wave energy from the lakes.

Transportation

The Great Lakes and surrounding area is a natural resource of great importance in North America. The region also serves as the focal point of the industrial and agricultural base of the Midwest's heartland by providing a strong marine transportation system. Rivers, straits, canals, locks, and channels interconnect the Great Lakes, and together form one of the busiest shipping arteries in the world.*

With the 1959 completion of the St. Lawrence Seaway, the commercial potential of the lakes increased because they could now accommodate medium-sized oceangoing vessels. In fact, the St. Lawrence Seaway brought several Great Lakes ports closer to European markets than existing East Coast or Gulf ports, saving shippers both time and money. For example, the shipping distance from the port city of Baltimore, Maryland, to Liverpool, England, is 6,334 kilometers (3,936 miles). With the addition of the St. Lawrence Seaway, ships could reach Detroit, Michigan by covering only 5,911 kilometers (3,673 miles).

The Great Lakes today are home to the U.S. and Canadian flag fleets and to dozens of international vessels from ports around the world. The movement of shipping cargo is estimated to provide approximately 60,000 jobs throughout the Great Lakes region. The ability to efficiently ship materials such as iron ore, coal, and limestone enabled the rise of the steel and automobile industries in the Great Lakes region.

Recreation

Recreation in the Great Lakes area became important beginning in the nineteenth century. A thriving pleasure-boat industry based on newly constructed canals on the lakes brought vacationers into the region, as did the already established railroads and highways. The lower lakes wilderness region attracted people who were seeking health benefits and even miracle cures from mineral waters.

In the twentieth century, the U.S. and Canadian governments acquired border lands to develop a system of parks, wilderness areas, and conservation areas in order to protect valuable resources and to serve the recreational needs of the population. Unfortunately, by the time the need for publicly accessible recreation lands had become apparent, much of the land, including nearly all the shoreline on the lower lakes, was privately held. Today, about 80 percent of the U.S. shoreline and 20 percent of the Canadian shore is privately owned.

Niagara Falls was one of the first Great Lakes tourist attractions, and it remains a popular destination. Niagara Falls were formed approximately 10,000 years ago when retreating glaciers exposed the Niagara escarpment, allowing the waters of Lake Erie to flow north to Lake Ontario. Until the early 1950s, the falls eroded at an average rate of 1 meter (3 feet) per year, but human modifications to the river's flow have since reduced the rate of erosion. Today, Goat Island splits the rapids into the American Falls (51 meters or 167 feet high and 323 meters or 1,060 feet wide) and the Horseshoe, or Canadian, Falls (48 meters and 158 feet high and 792 meters or 2,600 feet wide).

Great Lakes Fisheries

The Great Lakes support diverse fresh-water fisheries. Fish were a primary source of food to Native tribes of the Great Lakes region, and settlements often were established at places where the fisheries were good. Sturgeon, lake trout, and whitefish were popular catches of their time. Birchbark canoes and nets made from willow bark were commonly used to harvest fish. Tribal fishermen also practiced ice fishing, spearing through the ice and fishing with hand-carved decoys. Fish also were an important source of food to the early European settlers.

Commercial fishing began around 1820, and annual catches grew approximately 20 percent per year as improved fishing technologies were applied. During the 1880s, some species in Lake Erie began to decline. Commercial fishing harvests from the Great Lakes peaked between 1889 and 1899 at around 67,000 metric tons (147 million pounds).

By the late 1950s, the golden days of the Great Lakes commercial fishery were over. Since that time, average annual catches have been approximately 50,000 metric tons (110 million pounds). The fishery is increasingly dominated by smaller and relatively lower valued species. Moreover, the fishery is a mix of native and introduced species, with a number of species being restocked regularly. While each of the Great Lakes has its own mainstay species, common catches currently include lake trout, salmon, walleye, perch, whitefish, smallmouth bass, steelhead, and brown trout.*

In the 100 years since its peak harvests, the Great Lakes fishery has been severely threatened, mainly due to the effects of overfishing, shoreline and stream habitat destruction, and pollution. The accidental and deliberate introductions of nonnative invasive species, such as the sea lamprey and zebra mussel, have also played a role in the decline of this fishery. Today, only isolated pockets of the once large commercial fishery remain, and even these are uncertain, due largely to contaminants . Efforts undertaken to stabilize the commercial fishery have maintained its commercial and sport value at more than $4 billion annually as of 2002.

Environmental Degradation

The degradation of the Great Lakes can be traced back to the westward expansion of the North American population. The fishery decline in late 1800s was one of the region's earliest environmental problems. Agricultural and forestry practices resulted in siltation, increased water temperature, and loss of habitat for native fish species. The discharge of pollutants into the lakes accompanied the region's population growth. The vastness of the Great Lakes encouraged the mistaken belief that their great volumes of water could indefinitely dilute pollutants to harmless levels.

Yet impacts to the environment and human health were inevitable. The direct discharge of domestic wastes from cities along the lakeshores led to typhoid and cholera epidemics in the early 1900s. Moreover, fish would become so contaminated by municipal and industrial pollutants that their flesh was no longer safe to eat.

In 1909, the United States and Canada cooperatively negotiated the Boundary Waters Treaty. This treaty established the International Joint Commission (IJC) which is a permanent binational body addressing, among other important boundary issues, water quality concerns and the regulation of water levels and flows between the two countries. The Great Lakes Water Quality Board and the Great Lakes Science Advisory Board are bodies of the IJC. Six commissioners are the final arbitrators of the IJC: the United States and Canada appoint three each.

Several key water agreements have been produced by the International Joint Commission process, most notably the 1972 and 1978 Great Lakes Water Quality Agreements. Since the 1972 agreement, forty-three Areas of Concern (AOC) have been identified, twenty-six located within the United States, twelve located within Canada, and five that are shared by both countries.

Primarily due to the declining condition of Lake Erie, the 1978 Agreement went beyond setting narrow water-quality goals and addressed toxic contamination from an ecosystem perspective. This 1978 agreement has become a driver of the ecosystem approach to water management throughout the Great Lakes basin, and further amendments were passed in 1987. The 1987 U.S. Clean Water Act (Section 118) also addressed the Great Lakes situation and included provisions for monitoring of their water quality.

The Story of Lake Erie.

Reports since the 1950s of the "death" of Lake Erie serve as a reminder of the human impact on natural ecosystems. In the 1950s and 1960s, the Cuyahoga River, which empties into Lake Erie, caught fire due to oily pollutants on its surface.* Pollution problems from organic and inorganic wastes and nutrients were compounded by the effects of deforestation, sedimentation, and wetland drainage. Floating raw sewage, algal blooms, and the buildup of toxic metals in its sediments caused beach closings, oxygen depletion, contaminated fish advisories, and reports of the lake's death. Many feared the other lakes would follow a similar demise.

Concerted management efforts were undertaken in the 1970s to restore Lake Erie and the other lakes back to health. Yet after more than two decades of mostly good news about the lake's improving health, Lake Erie again is showing signs of an environmental crisis. Scientists attribute diverse and complex causes to the latest ecosystem disruption: large-scale fish and bird die-offs; a large "dead zone" off the Ohio shoreline; and the threat of invasion by more nonnative species, particularly the Asian carp and quagga mussel.

Renewed Concerns Over Water Levels

Measurements of water levels in the great Lakes constitute one of the longest continuous hydrometeorological datasets in North America. Reference gage records start in 1860, with sporadic records going back to the early 1800s.

Water levels on the Great Lakes change seasonally each year and can vary dramatically over longer periods. Seasonally, changes are to be expected, and the range of seasonal water-level fluctuation averages about 0.3 to 0.45 meters (12 to 18 inches) from winter lows to summer highs. Long-term fluctuations are harder to predict, and occur over periods of consecutive years. Over the last century, the range from extreme high to extreme low water levels has been nearly 1.2 meters (4 feet) for Lake Superior, and between 1.8 and 2.1 meters (6 to 7 feet) for the other Great Lakes.

As of 2002, the Great Lakes apparently were starting to recover from water-level lows not recorded since the mid-1960s. The declines probably were due predominantly to evaporation during the warmer-than-usual temperatures experienced during the late 1990s, a series of mild winters, and the below-average snowpack melts in the Lake Superior basin. Lower water levels have a variety of effects, including affecting shipping, recreation, property values, and habitat diversity. Concerns relating to potential impacts of global climate change on the Great Lakes are being researched.

Diversion of Great Lakes Waters

Proposals to divert water from the Great Lakes hydrologic system have proven very controversial. As these lakes are a shared international resource, many governments and organizations are concerned with managing and protecting the integrity of the Great Lakes waters and ecosystem. For these groups, the bulk export of Great Lakes basin water is an increasing concern in a water-scarce world.

Existing diversions comprising sizable quantities of water involve Ontario, Canada; Chicago, Illinois; and the intrabasin transfers of the Welland Canal. These diversions have been operational since the early 1900s. Much smaller diversions involve New York, Wisconsin, Ohio (via the City of Akron), and Michigan (via the City of Detroit).

Since 1995, new diversion and export schemes have included:

  • a permit granted to Perrier to bottle water from an aquifer in Michigan;
  • a plan to divert millions of liters of groundwater per day from Lake Michigan's watershed for use in mining-related activities that would discharge much of the diverted water into the Mississippi River Basin;
  • a permit issued by the Canadian province of Ontario for the bulk transfer of water from Lake Superior for sale in Asian markets as bottled water (but this permit was later revoked); and
  • a 2002 proposal by the City of Detroit to bottle and sell water from the Detroit River.

Water diversions and exports have come under intense scrutiny, especially as the lake levels were falling and reached near-record lows. As levels rise, many see opportunities to use the waters of the Great Lakes for commercial uses and to make profits. A debate also has intensified over whether groundwater is part of "Great Lakes waters" as defined by the Water Resources Development Act of 1986.

Two policies have been enacted to attempt to govern potential diversions from the Great Lakes basin: the Boundary Waters Treaty of 1909 and the Great Lakes Charter of 1985. The Boundary Waters Treaty expresses a commitment by both countries to refrain from harming the waters of the other country (e.g., due to bulk exports). The Great Lakes Charter specifically urges U.S. governors and Canadian premiers in the region to seek each other's approval prior to granting diversion requests for large-volume bulk exports above a threshold level; however, this is a nonbinding treaty.

Additionally, U.S. diversions from the Great Lakes may also be subject to the Water Resources Development Act of 1986 (amended in 2000). This act requires the approval by all eight U.S. Great Lakes governors on any proposed exports out of the basin. Within the region, many are concerned that this policy is not strong enough to protect the lakes from diversions and several pieces of legislation have been introduced into Congress to help prevent future diversions and even to create a moratorium on these bulk exports.

While efforts to protect Great Lakes waters surely will continue, international free trade agreements may clear the path for additional diversions, bulk removals, or the selling of bottled water. On the other hand, ongoing concerns over impacts on lake levels and potential consequences from climate change may spur new laws and treaties to prevent future diversions and exports from the basin.

Future of the Great Lakes

Managing the Great Lakes system and implementing an ecosystem approach are made difficult by the myriad of agencies and programs with responsibility in this area. Two countries, eight states, two provinces, and numerous tribal councils and local jurisdictions share an interest in managing the waters of the Great Lakes. Many local citizens groups have also formed to address water issues.

A 2002 report by the International Joint Commission concluded that progress to restore and maintain the chemical and biological integrity of the waters of the Great Lakes basin ecosystem is making some progress, but proceeding at a slow pace. It also stated that cleaning up contaminated sediments and stopping the invasion of alien species are two top priorities for restoring the chemical and biological integrity of this ecosystem. The Great Lakes basin has and will continue to serve as a vast laboratory where scientists can learn more about both ecosystem and water management.

see also Algal Blooms in Fresh Water; Canals; Clean Water Act; Economic Development; Environmental Movement: Role of Water in the; Fisheries, Fresh-Water; International Cooperation; Lake Management Issues; Pollution by Invasive Species; Pollution of Lakes and Streams; Pollution Sources: Point and Nonpoint; Ports and Harbors; Recreation; Tourism; Transboundary Water Treaties; Transportation.

Faye Anderson

and William Arthur Atkins

Bibliography

Ashworth, William. Great Lakes Journey: A New Look at America's Freshwater Coast. Detroit, MI: Wayne State University Press, 2000.

MacKenzie, Susan Hill. Integrated Resource Management: The Ecosystem Approach in the Great Lakes Basin. Washington, D.C.: Island Press, 1996.

Internet Resources

Great Lakes Commission. <http://www.glc.org/>.

Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration. <http://www.glerl.noaa.gov/>.

Great Lakes Fishery Commission. <http://www.glfc.org>.

Great Lakes Information Network. <http://www.great-lakes.net/>.

International Joint Commission. <http://www.ijc.org>.

The Great Lakes: An Environmental Atlas and Resource Book Government of Canada and U.S. Environmental Protection Agency. <http://www.epa.gov/glnpo/atlas/intro.html>.

LAKE SUPERIOR IS APTLY NAMED

Lake Superior is the largest lake with respect to both surface area and volume of water. It is also the deepest and coldest of the five lakes. If filled with the smaller lakes, Lake Superior could contain each of the other four Great Lakes and three more lakes the size of Lake Erie. The northwestern section of Lake Superior contains the archipelago of Isle Royale National Park.

* See "Army Corps of Engineers, U.S." for a photograph of a vessel at the Soo Locks.

* See "Fisheries, Fresh-Water" for a photograph of a recreational fisher holding a Lake Michigan steelhead.

* See "Environmental Movement, Role of Water in the" for a photograph of the 1952 Cuyahoga River fire.

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Great Lakes

GREAT LAKES

GREAT LAKES. The Great Lakes, also called the Inland Seas, consist of five connecting freshwater lakes in east central North America that straddle the international border between Canada and the United States. Collectively they constitute the world's largest body of freshwater, with a surface area of 94,000 square miles (244,000 sq. km) and 5,500 cubic miles (23,000 cu. km) of water. The lakes contain approximately 18 percent of the world's supply of freshwater, with only the polar ice caps having more. From west to east, the lakes are Superior (the largest and deepest of the lakes), Michigan, Huron, Erie (the shallowest), and Ontario (the smallest); they collectively extend about 850 miles (1370 km) west to east and 700 miles (1125 km) from north to south. The Great Lakes form the western portion of the greater St. Lawrence hydrographic system, extending from Minnesota to the Atlantic Ocean.

Lake Superior connects to Huron through Sault Sainte Marie (St. Marys River), and Lake Michigan joins Huron via the Straits of Mackinac. A major inlet north of Lake Huron is Georgian Bay, which lies entirely within Canada. Waters from the three upper Great Lakes (Superior, Michigan, and Huron) flow through the St. Clair River, Lake St. Claire, and the Detroit River into Lake Erie, which in turn is connected to Lake Ontario through the Niagara River and Niagara Falls. The five lakes then drain northeastward into the Atlantic Ocean through the St. Lawrence River. The Great Lakes' drainage basin covers 295,200 square miles (764,570 sq. km) and includes portions of eight states (Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York) and the Canadian province of Ontario, which extends along the north shore of four of the lakes. Lake Michigan lies entirely within the boundaries of the United States; the international boundary bisects the other four lakes.

Geologically, the Great Lakes system began to develop three million years ago, during the Precambrian Era, a time of volcanic activity and geological stress that formed major mountain systems that later eroded. Most of central North America was covered by marine seas during the Paleozoic Era, and major continental glaciers advanced over the Great Lakes region beginning about one million years ago. As a result of a series of glacial formations and retreats, glacial deposits and large volumes of meltwater created a basin larger than the present-day Great Lakes. The most recent Great Lakes basin formed between 32,000 and 10,000 years ago; lake levels stabilized about 2,400 years ago. Five biotic provinces are defined on the basis of floral and faunal characteristics, and include Hudsonian to the extreme north, Canadian (Georgian Bay, Lake Nipissing, and the Ottawa River), Carolinian-Canadian Transition (present-day Wisconsin, Michigan, and southern Ontario), Illinoisan (southern Lake Michigan basin), and Carolinian (Ohio, Pennsylvania, and western New York).

Paleo-Indian hunters and gatherers occupied the Great Lakes basin before 9500 b.c.e. and were followed by semisedentary Early Archaic peoples who exploited a wider variety of large and small fauna and diverse flora. More populous and technologically advanced Late Archaic peoples formed small sedentary communities beginning in 3,000 b.c.e. The Archaic-Woodland Transition (1500100 b.c.e.) was characterized by large sedentary villages, plant domestication, the development of pottery, and cultural adaptations to diverse econiches. The Middle Woodland period (c. 200 b.c.e.500 c.e.) saw the development of Hopewell culture in Ohio and adjacent states, characterized by circular and serpentine earthworks, enormous artificial mounds, elaborate burial practices, and long-distance trade systems for exotic goods used in burials, such as marine shells from Florida and obsidian from Wyoming. Other areas of the Great Lakes continued an Early Woodland pattern.

The subsequent Late Woodland period (5001600 c.e.) saw the incursions of peoples and ideas from the Mississippi Valley; an emphasis on the cultivation of maize, beans, squash, and sunflowers; larger populations and settlements; and territorial conflicts between tribes. At European contact a number of major tribes were established in the Great Lakes basin, among them the Ojibwe, Me-nominee, Winnebago, Miami, Potawatomi, Fox, Sauk, Kickapoo, and Mascouten tribes in the upper Great Lakes region, and the Erie, Iroquois (Seneca, Oneida, Cayuga, Onondaga, and Mohawk), and Wenro south of lakes Erie and Ontario, with the Ottawa, Petun, Huron, and Neutral tribes north of those lakes. Miamis, Mascoutens, Mesquakies, and Shawnees occupied the area around Lake Michigan.

The French explorer Jacques Cartier, seeking a northwest passage to the Orient, located the St. Lawrence River during the years of 1534 and 1535. Samuel de Champlain visited lakes Ontario and Huron in 1610, initiating a period of French exploration characterized by missionaries, fur traders, and territorial conflicts between the emerging New France and British colonies along the Atlantic seaboard. The Ottawa River provided a route for Jesuit missionaries and French trappers and traders, who soon visited the upper lakes. Jean Nicolet reached the shores of

Table 1

Great Lakes: Physical Features and Population
a. Measured at Low Water datum.
b. Land drainage area for Lake Huron includes St. Marys River; for Lake Erie includes the St. Clair-Detroit system; for Lake Ontario includes the Niagara River.
c. Including islands.
d. These totals are greater than the sum of the shoreline length for the lakes because they include the connecting channels (excluding the St. Lawrence River).
source: Government of Canada and United States Environmental Protection Agency (1995), 4.
Superior Michigan Huron Erie Ontario Combined
Elevationa (feet) 600 577 577 569 243
Length (miles) 350 307 206 241 193
Breadth (miles) 160 118 183 57 53
Average Deptha (feet) 483 279 195 62 283
Maximum Deptha (feet) 1,332 925 750 210 802
Volumea (cu mi) 2,900 1,180 850 116 393 5,439
Water Area (sq mi) 31,700 22,300 23,000 9,910 7,340 94,250
Land Drainage Areab (sq mi) 49,300 45,600 51,700 30,140 24,720 201,460
Total Area (sq mi) 81,000 67,900 74,700 40,050 32,060 295,710
Shoreline Lengthc (miles) 2,726 1,638 3,827 871 712 10,210d
Retention Time (years) 191 99 22 2.6 6
Outlet St. Marys River Straits of Mackinac St. Clair River Niagara River/Welland Canal St. Lawrence River
Population U.S. (1990) 425,548 10,057,026 1,502,687 10,017,530 2,704,284 24,707,075
Canada (1991) 181,573 1,191,467 1,664,639 5,446,611 8,484,290
Totals 607,121 10,057,026 2,694,154 11,682,169 8,150,895 33,191,365

Lake Michigan in 1634, and Isaac Jogues and Charles Raymbault ventured to Sault Sainte Marie seven years later. By 1672 the Jesuits had compiled and published an accurate map of Lake Superior. The Iroquois Wars (16411701) and a period of French incursion, settlement, and fortifications (17201761) followed. By 1673 Louis Jolliet and Jacques Marquette had begun explorations of the upper Mississippi River, followed by Robert Cavelier, Sieur de La Salle, and his expedition (16781684). By 1683 a highly accurate map of all the Great Lakes, based on these and other expeditions and journeys, was compiled by Father Louis Hennepin.

Drawn by the fur trade and seeking new lands, English traders from Albany began to explore the upper Great Lakes in the 1690s. To counter this, in 1701 Antoine de la Mothe Cadillac established Fort Pontchartrain du Détroit, which commanded the narrow river between Lake Erie and Lake Huron. It became the focus of French control of the upper lakes and denied access to English traders and exploration. The conflict between the English and French for the control of North America, which centered on the Great Lakes, involved a series of wars and minor conflicts that covered a period of seventy-five years and included participation by Native Americans on both sides. The French and Indian War culminated with the surrender of French Canada to the British in 1760. Pontiac's War (17631764) heralded a transitional period with American exploration, migrations, and settlement of the region along the southern shores of the Great Lakes. Notably the Definitive Treaty of Peace signed between Britain and the United States in 1783, ending the Revolutionary War, included an article that called for control of the lakes to be shared between British Canada and the American colonies.

The War of 1812 (18121815), between the Americans and the British, also involved Native Americans on both sides in the region of Detroit and the Niagara Frontier. Many of the engagements were fought on and adjoining the Great Lakes. A major naval engagement, the battle of Lake Erie (10 September 1813), was won by the Americans and helped to ensure the sovereignty of the United States through the Treaty of Ghent (1814) and the Rush-Bagot Agreement (1817), which established limitations on naval forces on the Great Lakes.

The promise of agricultural land was a major attraction for immigrants; hence agrarian settlements and fisheries developed on both the American and the Canadian sides of the border during the 1800s. City building, nation building, and industrialization were hallmarks of the nineteenth century as dairying, fruit and vegetable cultivation, logging, and forest exploitation gave way to iron and steel production, papermaking, and chemical manufacture in the twentieth century. The forests around the Great Lakes provided hardwoods and pine, while the Lake Superior region yielded high-quality iron ore and copper. Major agricultural products included corn, wheat, soybeans, grapes, pork, and beef cattle. The industry of the region was, and remains, highly diversified, but significant quantities of iron ore, coal, minerals, grain, and manufactured products are transported throughout the Great Lakes and shipped overseas. Notable transportation improvements included the construction of the Erie Canal, from Albany to Buffalo, New York (completed in 1825); the Canadian Lachine Canal, bypassing rapids in the St. Lawrence River; and the Welland Canal (1829), joining lakes Erie and Ontario. The latter two were surpassed in 1959 by the completion of the St. Lawrence Seaway.

Commercial fishing began about 1820 and peaked between 1889 and 1899 but native fish diminished and have been replaced by introduced species. Sport fishing, water recreation, and cultural tourism have become economically significant in spite of a deterioration in water quality and habitat that accompanied urbanization and industrialization. Pollution, pathogens, eutrophication, toxic contaminants, diminished oxygen levels, the introduction of exotic flora and fauna (such as zebra mussels), and a recent drop in lake water levels are of major concern to inhabitants of the Great Lakes basin.

Perhaps surprisingly, a number of upper Great Lakes cities were founded earlier than many of the settlements situated along the shores of the lower lakes. In the main lakes the early settlements were fur trading posts, such as Green Bay in modern Wisconsin at the mouth of the Fox River, established in 1634 and with a population of more than 103,000 by 2000. Other posts were established at Chicago in 1673; at Thunder Bay, Ontario, in 1678; and at Duluth, Minnesota, in 1692. In the lower lakes Hamilton, Ontario, was established in 1669 and by 2000 was an industrial center with 320,000 inhabitants; Buffalo, New York, a former Seneca Indian village settled by Europeans in 1679, was by 2000 an industrial city with more than 300,000 inhabitants. Detroit, settled in 1701, has become a center of automotive production and has a population exceeding 1,045,000 in 2000. Established in 1720, Toronto, now the capital of the province of Ontario and a financial and commercial center, had a 2000 census of 640,000. Because explorers, missionaries, and travelers could bypass Lake Erie by venturing from Lake Ontario and the Ontario River to the upper lakes, settlements along Lake Erie were founded late in the region's history. These include Erie, Pennsylvania, in 1753 (in 2000 an industrial and agricultural community of 105,000); Cleveland, Ohio, in 1786 (a major center of heavy industry with a population exceeding 506,000 in 2000); London, Ontario, in 1792 (by 2000 an industrial and agricultural center with more than 303,000 persons); and Toledo, Ohio, in 1794 (another industrial community, with 323,000 persons in 2000). Rochester, New York, now a center for imaging science, was founded on the Genessee River, which flows into Lake Ontario, in 1789; Milwaukee, Wisconsin, situated at the mouth of the river of the same name, was founded in 1800 and was a major center of the brewing industry. In 2000 Rochester had a population of 217,000, and Milwaukee's census exceeded 617,000. Chicago grew from a trading post to become a leading rail and lake transport hub, as well as an industrial and commercial center with a population of 2,840,000 in 2000.

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Skaggs, David C. A Signal Victory: The Lake Erie Campaign. 18121813. Annapolis, Md.: Naval Institute Press. 1997.

St. John, John R. A True Description of the Lake Superior Country. Grand Rapids, Mich.: Black Letter-Press, 1976.

Tanner, Helen H., ed. Atlas of Great Lakes Indian History. Norman: University of Oklahoma Press for The Newberry Library, 1987.

Thompson, Mark L. Graveyard of the Lakes. Detroit: Wayne State University Press, 2000.

Thwaites, Reuben Gold. The Jesuit Relations and Allied Documents. 73 vols. Cleveland: Burrows Brothers, 18961901.

Charles C. Kolb

See also Explorations and Expeditions: French ; Michigan, Upper Peninsula of ; Tribes .

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Great Lakes

Great Lakes

The Great Lakes are a system of five large freshwater lakes in central North AmericaLake Erie, Lake Huron, Lake Michigan, Lake Ontario, and Lake Superiorthat drain into the Atlantic Ocean via the St. Lawrence Seaway. Combined, the Great Lakes constitute the largest surface area of unfrozen fresh water in the world: 94,850 mi2 (245,660 km2), an area larger than the United Kingdom. Except for Lake Michigan, which is wholly contained in the United States, the Great Lakes form a natural segment of the U.S.-Canadian border.

Lake Superior is the largest of the five lakes by almost 10,000 mi2 (41,682 km2), and has the greatest average (and maximum) depth. As a result, Lake Superior contains slightly more water than all the other Great Lakes combinedalmost 3,000 mi3 (12,504 km3). The deepest parts of all the Great Lakes except Lake Erie are below sea level; in Lake Superior's case, over 600 ft (183 m) below.

Lake Superior has an average depth of 487 ft (148 m), a maximum depth of 1,302 ft (397 m) and covers 31,820 mi2(82,413 km2). Lake Huron has an average depth of 195 ft (59m), a maximum depth of 750 ft (229 m), and covers 23,010 mi2 (59,596 km2). Lake Michigan, covering 22,400 mi2(58,016 km2), has an average depth of 276 ft (84 m), and a maximum depth of 923 ft (281 m). Lake Erie has an average depth of 62 ft (19 m), a maximum depth of 210 ft (64 m), and covers approximately 9,930 mi2 (25,719 km2). Lake Ontario, the smallest of the Great Lakes in terms of surface area (7,520 mi2/19,477 km2), has an average depth of 62 ft (19 m) but reaches a maximum depth of 778 ft (237 m).

The Great Lakes drain 295,800 mi2 (766,118 km2) of watershed (counting the surfaces of lakes themselves), or about 3% of the continent. Half the water entering the lakes evaporates; the rest flows from lake to lake, west to east, until it reaches Lake Ontario and then the St. Lawrence River.

By geological standards, the Great Lakes formed very recently. Prior to the beginning of the ice ages of the Pleistocene Epochabout 1 million years agoriver valleys drained through the areas now occupied by the five lakes. As the ice-sheets flowed southward they favored these preexisting channels, scouring them and so increasing their depth. The latest glacial episode was the Wisconsin Glaciation , which ended about 18,000 years ago. When melting removed the glacier's enormous weight, the land began to rise. (It is still rising, at about .12 in / 3 mm per year.) This rising of the land, along with deposition of glacial sediments (moraines ), blocked all drainage from the Great Lakes area except eastward via the St. Lawrence. Lake Superior is the only Great Lake not formed by glacial scouring and deposition of moraines. Lake Superior's basin, although somewhat enlarged by glacial scouring, is the trough of a V-shaped fold in the rock termed a syncline .

But the Wisconsin glaciation did not simply advance to a most southerly limit, then retreat in an orderly way. It advanced and retreated several times over thousands of years in a three-steps-northward, two-steps-southward fashion. These oscillations partially uncovered and recovered the Great Lakes basins, forming a series of lakes corresponding partly to the modern ones. At one point, a superlake submerged what are today the basins of Superior, Michigan, and Huron. The history of these fluctuations can be traced primarily by the many abandoned beaches that are today found far above water level (often hundreds of feet above). Each abandoned beach records a lake stage or period during which the water level was stable long enough to form a beach. From these and other data, it is known that Erie reached its present level about 10,000 years ago; Ontario about 7,000 years ago; and Superior, Michigan, and Huron only about 3,000 years ago.

Human activity has significantly altered the chemistry and ecology of the lower four lakes, which are ringed by such cities as Buffalo, Chicago, Cleveland, Detroit, Gary, Milwaukee, Rochester, Toledo, and Toronto. Sewage and industrial effluents have burdened these lakes increasingly for over a century. (Chicago and several other cities, however, now divert their sewage southward, away from the lakes.) Lake Superior has been less affected by pollution, having no major settlements on its shores.

Another detrimental side-effect of human activity is the introduction into the lake ecosystem, both deliberate and accidental, of non-native species. The sea lamprey (1930s), alewife (probably 1940s), and zebra mussel (1980s) have been particularly destructive to the native lake fauna. Alewives are now the most abundant fish species in the lakes. They suffer intermittent mass die-offs, wash up on the beaches by the millions, and must be removed using bulldozers and trucked away.

See also Drainage basins and drainage patterns; Glacial land-forms; Syncline and anticline; Water pollution and biological purification

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Great Lakes (North America)

Great Lakes, group of five freshwater lakes, central North America, creating a natural border between the United States and Canada and forming the largest body of freshwater in the world, with a combined surface area of c.95,000 sq mi (246,050 sq km). From west to east they are Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, out of which flows the Saint Lawrence River. The distance from Duluth, Minn., at the western end of Lake Superior, to the outlet of Lake Ontario is 1,160 mi (1,867 km). The international boundary passes approximately through the center of all the lakes except Lake Michigan, which lies entirely within the United States.

The Great Lakes were formed approximately at the end of the Pleistocene period, when the glacier-carved lake basins were filled with meltwater from the retreating ice sheet. The lakes are connected to each other by straits, short rivers, and canals. The height above sea level of the lake surfaces varies from Lake Superior's 602 ft (183 m) to Lake Ontario's 246 ft (75 m); the greatest sudden drop occurs at Niagara Falls (167 ft/51 m) between lakes Erie and Ontario; the water levels fluctuate over the months and years due to climatic changes. All the lake bottoms, except that of Lake Erie, extend below sea level.

French traders were the first Europeans to see any of the Great Lakes; Étienne Brulé visited Lake Huron c.1612. In 1614, Brulé and French explorer Samuel de Champlain explored Lake Huron and Lake Ontario. In 1679, the French explorer La Salle sailed from Lake Erie to Lake Michigan. The Great Lakes region, rich in furs, was contested for many years by the French, English, and Americans. The close of the War of 1812 finally ended the struggle for possession of the Great Lakes, and settlement of the region rapidly followed. The opening of the Erie Canal in 1825 accelerated the development of commerce on the Great Lakes.

The opening of the St. Lawrence Seaway in 1959 made the Great Lakes a truly international water body. The Illinois Waterway connects the lakes with the Mississippi River and the Gulf of Mexico; the New York State Canal System (including the Erie Canal) joins the Great Lakes with the Hudson River and the Atlantic Ocean. Shipping on the lakes carries large quantities of iron ore and grain, coal, and petroleum, and manufactured articles from April until December, until ice closes most of the ports and winter storms hinder navigation. The large industrial lakefront cities include Toronto, Hamilton, Buffalo, Cleveland, Detroit, Gary, Milwaukee, and Chicago. Large concentrations of population and industry along the lakes' shores led to pollution, especially of Lake Erie, but the condition of the lakes has improved since the 1960s. The Great Lakes region, with its national parks and lakeshores, state parks, and many natural and scenic features, has become an important year-round recreation area.

See J. Rousmaniere, ed., The Enduring Great Lakes (1979); C. E. Feltner and J. B. Feltner, Great Lakes Maritime History (1982); S. L. Flader, ed., The Great Lakes Forest (1983).

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Great Lakes

Great Lakes Five lakes in central North America, between Canada and the USA; the world's largest expanse of freshwater. They are (from w to e): Lakes Superior, Michigan, Huron, Erie, and Ontario. They interconnect by straits, rivers, and canals, providing a continuous waterway. They are drained by the St Lawrence River, the deepening of which opened up the lakes to world shipping. Industrial and commercial growth led to pollution. Major cities include Chicago, Toronto, Detroit, Buffalo, Cleveland, and Milwaukee. Total surface area: c.245,300sq km (94,700sq mi).

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