Great Lakes

2007 Schools Wikipedia Selection. Related subjects: General Geography

The Great Lakes from space
The Great Lakes from space

The Great Lakes are a group of five large lakes in North America on or near the Canada-United States border. They are the largest group of fresh water lakes on Earth. The Great Lakes- St. Lawrence system is the largest fresh-water system in the world. They are sometimes referred to as inland seas.


Lake Michigan
Lake Michigan
Lake Huron
Lake Huron
Lake Erie
Lake Erie
Lake Ontario
Lake Ontario

Great Lakes: System Profile
Great Lakes: System Profile

The Great Lakes are:

  • Lake Superior (the largest by volume and deepest, larger than Scotland or South Carolina)
  • Lake Michigan (the second-largest by volume and third-largest by area; the only one entirely in the U.S.)
  • Lake Huron (the third-largest by volume; the second largest in area)
  • Lake Erie (the smallest by volume and shallowest)
  • Lake Ontario (the second-smallest in volume and smallest in area, much lower elevation than the rest)
Map of the Great Lakes/St. Lawrence Watershed
Map of the Great Lakes/St. Lawrence Watershed

Lakes Michigan and Huron, being hydrologically intertwined, are sometimes considered to be one entity: Lake Michigan-Huron. Considered together, Michigan-Huron would be larger in surface area than Lake Superior, but smaller in total water volume.

A much smaller sixth lake, Lake St. Clair, is part of the Great Lakes system between Lake Huron and Lake Erie, but is not considered one of the "Great Lakes." The system also includes the rivers that connect the lakes: St. Marys River between Lake Superior and Lake Huron, the St. Clair River between Lake Huron and Lake St. Clair, the Detroit River between Lake St. Clair and Lake Erie, and the Niagara River and Niagara Falls, between Lake Erie and Lake Ontario. (Lake Michigan is connected to Lake Huron through the Straits of Mackinac.) Large islands and a peninsula divides Lake Huron into the lake proper and Georgian Bay.

The lakes are bounded by Ontario (all of the lakes but Michigan), Minnesota, Wisconsin, Michigan (all but Ontario), Illinois, Indiana, Ohio, Pennsylvania, and New York. Four of the five lakes straddle the U.S.-Canada border; the fifth, Lake Michigan, is entirely within the United States. The Saint Lawrence River, which marks the same international border for a portion of its course, is a primary outlet of these interconnected lakes, and flows through Quebec and past the Gaspé Peninsula to the northern Atlantic Ocean.

The Great Lakes are clearly visible in this satellite image of North America
The Great Lakes are clearly visible in this satellite image of North America

Sprinkled throughout the lakes are the approximately 35,000 Great Lakes islands, including Manitoulin Island in Lake Huron, the largest island in any inland body of water, and Isle Royale in Lake Superior, the largest island in the largest lake (each island large enough to itself contain multiple lakes).

Today, 20 percent of the world’s fresh surface water is contained in the five great lakes: 5,473 cubic miles (22,812 km³), or 6 quadrillion gallons (22.81 quadrillion litres) in all. It is enough water to cover the contiguous 48 states to a uniform depth of 9.5 feet (2.9 m). The combined surface area of the lakes is 94,250 square miles (244,100 km²)— larger than the states of New York, New Jersey, Connecticut, Rhode Island, Massachusetts, Vermont and New Hampshire combined.

The Saint Lawrence Seaway and Great Lakes Waterway opened the Great Lakes to ocean-going vessels. However the move to wider ocean-going container ships - which do not fit through the locks on these routes - has limited shipping on the lakes. Despite their vast size, large sections of the Great Lakes freeze over in winter, and most shipping stops during that season. There are some icebreakers that operate on the lakes.

The lakes have an effect on weather in the region, known as lake effect. In winter, the moisture picked up by the prevailing winds from the west can produce very heavy snowfall, especially along lakeshores to the east such as Indiana, Michigan, Ontario, and New York. It is not uncommon for heavy snow to occur during completely clear skies because of this phenomenon. The lakes also moderate seasonal temperatures somewhat, by absorbing heat and cooling the air in summer, then slowly radiating that heat in autumn. This temperature buffering produces areas known as "fruit belts", where fruit typically grown farther south can be produced in commercial quantities.

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's Great Lakes Atlas: Factsheet #1.

Geologic pre-history

The Great Lakes were formed at the end of the last ice age about 10,000 years ago, when the Laurentide ice sheet receded. When this happened, the glaciers left behind a large amount of meltwater (see Lake Agassiz) which filled up the basins that the glaciers had carved, thus creating the Great Lakes as we know them today. 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 -- Herbert Simon called this escarpment the spinal cord of my native land.


The lakes are extensively used for transport, though cargo traffic has decreased considerably in recent years. The Great Lakes Waterway makes each of the lakes accessible.

During settlement, the Great Lakes and its rivers were the only practical means of moving people and freight. Anything and everything floated on the lakes. Some ended up on the bottom because of storms, fires, collisions and underwater hazards. (See Edmund Fitzgerald and Le Griffon.) Barges from middle North America were able to reach the Atlantic Ocean from the Great Lakes when the Erie Canal opened in 1825. By 1848, with the opening of the Illinois and Michigan Canal at Chicago, direct access to the Mississippi River was possible from the lakes. With these two canals an all-inland water route was provided between New York City and New Orleans.

The main business of many of the passenger lines in the 1800s was transporting immigrants. Many of the larger cities owe their existence to their position on the lakes as a freight destination as well as for being a magnet for immigrants. After railroads and surface roads developed the freight and passenger businesses dwindled and, excepting ferries and a few foreign cruise ships, now has vanished.

Yet, the immigration routes still have an effect today. Immigrants often formed their own communities and some areas have a pronounced ethnicity, such as Dutch, German, Polish, Finnish, and many others. Since many immigrants settled for a time in New England before moving westward, many areas on the U.S. side of the Great Lakes also have a New England feel, especially in home styles and accent.

Since general freight these days is transported by railroads and trucks (lorries), domestic ships mostly move bulk cargoes, such as iron ore and its derivatives, coal and limestone for the steel industry. The domestic bulk freight developed because of the nearby mines. It was more economical to transport the ingredients for steel to centralized plants rather than try to make steel on the spot. Ingredients for steel, however, are not the only bulk shipments made. Grain exports are also a major shipping commodity on the lakes.

In the 19th and early 20th centuries, iron and other ores such as copper were shipped south on (downbound ships) and supplies, food staples, and coal was shipped north (upbound). Because of the location of the coal fields in Pennsylvania and West Virginia, and the general northeast track of the Appalachian Mountains, railroads naturally developed shipping routes that went due north to ports such as Erie, Pennsylvania and Ashtabula, Ohio.

Because the lake maritime community largely developed independently, it has its own language. Ships, no matter the size, are referred to as boats. When the sailing ships gave way to steamships, they were called steamboats—the same term used on the Mississippi. The ships also have a distinctive design. Ships that primarily trade on the lakes are known as lakers. Foreign boats are known as salties.

One of the more common sights on the lakes is the 1,000 by 105-foot (305 by 32-m), 60,000 U.S. long tons (61,000 metric tonnes) self-unloader. This is a laker with a huge conveyor belt system that can unload itself by swinging a crane over the side. Today, the Great Lakes fleet is much smaller in numbers than it once was because of the increase use of overland freight and the use of larger ships replacing the need for many smaller ships.

Modern economy

The Great Lakes are used as a major mode of transport for bulk goods. The brigantine Le Griffon, which was commissioned by René Robert Cavelier, Sieur de La Salle, was built at Cayuga Creek, near the southern end of the Niagara River, to become the first sailing ship to travel the upper Great Lakes on August 7, 1679.

In 2002, 162 million net tons of dry bulk cargo was moved on the Lakes. This was, in order of volume: iron ore, coal, stone, grain, salt, cement and potash. The iron ore and much of the stone and coal are used in the steel industry. There is also some shipping of liquid and containerized cargo but most container ships cannot pass the locks on the Saint Lawrence Seaway because they are too wide. The total amount of shipping on the lakes has been on a downward trend for several years.

Wolfe Islander III, Kingston, Ontario
Wolfe Islander III, Kingston, Ontario

Recreational boating and tourism are major industries on the Great Lakes. A few small cruise ships operate on the Great Lakes including a couple of sailing ships. Sport fishing, commercial fishing, and Native American fishing represent a US$4 billion a year industry with salmon, whitefish, smelt, lake trout, and walleye being major catches.

The Great Lakes are used to supply drinking water to tens of millions of people in bordering areas. This valuable resource is collectively administered by the state and provincial governments adjacent to the lakes.

Passenger traffic

Several ferries operate on the Great Lakes to carry passengers to various islands, including Isle Royale, Pelee Island, Mackinac Island, Beaver Island, both Bois Blanc Islands, Kelleys Island, South Bass Island, North Manitou Island, South Manitou Island, Harsens Island, Manitoulin Island, and the Toronto Islands. As of 2005, three car ferry services cross the Great Lakes: a steamer across Lake Michigan from Ludington, Michigan to Manitowoc, Wisconsin; a high speed catamaran on a second Lake Michigan route from Milwaukee to Muskegon, Michigan. An international ferry across Lake Ontario from Rochester, New York to Toronto ran during the summer of 2004, but is no longer in operation.


Travel on the Lakes has not been without risks. There are parts where no land is visible because of the immense size of the Lakes: thus they are sometimes referred to as inland seas.

Storms and reefs are a common threat, and many thousands of ships have sunk in these waters. It is estimated that between 6,000 and 10,000 ships have sunk or been stranded since the early 1800s, many with partial or total loss of crew. This area is prone to sudden and severe storms, particularly in the autumn from late October until early December. The Great Lakes Storm of 1913 became the worst Great Lakes storm on record: at least 12 ships sank, and 31 more were stranded on rocks and beaches. At least 248 sailors lost their lives over that weekend. The SS Edmund Fitzgerald, which sank November 10, 1975, was famously the last major freighter lost on the lakes. For many years in the late 1700s and early 1800s, wars were fought over the control of the Lakes and many warships were built for the inland seas, ranging from small and swift sloops-of-war to three-deckers capable of standing in any line of battle. USS Freedom (LCS-1) is the newest warship to be built on the Great Lakes. The Rush-Bagot Agreement of 1817 limits the number of armed vessels permitted on the Great Lakes.

The greatest concentration of these wrecks lies near Thunder Bay (Michigan), beneath Lake Huron, near the point where eastbound and westbound shipping lanes converge. Today there is a U.S. NOAA Marine Archeology Research Station located in the Thunder Bay National Marine Sanctuary. Here divers can explore more than 200 shipwrecks that form one of the most concentrated and best preserved maritime archaeology sites in the world.

Invasive species

The Great Lakes have been hit economically by various invasive species, namely the sea lamprey, Quagga mussel, and zebra mussel. The mussels clog pipes leading to the lakes and causes approximately US$1 billion in damages per year while destroying native species. The lamprey feeds on the sport fish of the lakes, making them less attractive to fishermen. An electric fence has been set up across the mouth of the Great Lakes in order to keep an invasive species of Asian carp out of the area.

Political issues

Great Lakes Water Use and Diversions

The International Joint Commission was established in 1909 to help prevent and resolve disputes relating to the use and quality of boundary waters, and to advise Canada and the United States on questions related to water resources. Concerns over diversion of Lake water are of concern to both Americans and Canadians. Some water is diverted through the Chicago River to operate the Illinois Waterway but the flow is limited by treaty. Possible schemes for bottled water plants and diversion to dry regions of the continent raise concerns. Under the U.S. "Water Resources Development Act" , diversion of water from the Great Lakes basin requires the approval of all eight Great Lakes governors, which rarely occurs. International treaties regulate large diversions. In 1998, the Canadian company Nova Group won approval from the Province of Ontario to withdraw 158,000,000 US gallons (600,000 m³) of Lake Superior water annually to ship by tanker to Asian countries. Public outcry forced the company to abandon the plan before it began. Since that time, the eight Great Lakes Governors and the Premiers of Ontario and Quebec have negotiated the Great Lakes-St. Lawrence River Basin Sustainable Water Resources Agreement and the Great Lakes-St. Lawrence River Basin Water Resources Compact that would prevent most future diversion proposals and all long-distance ones. The agreements also strengthen protection against abusive water withdrawal practices within the Great Lakes basin. On December 13, 2005, The Governors and Premiers signed these two agreements: the first is between all ten jurisdictions. It is somewhat more detailed and protective, but cannot be enforced in court because enforcement arrangements can be made only between the federal governments. The second is just between the U.S. states, which, if approved by all eight state legislatures which border the Great Lakes and the U.S. Congress, could be enforced in U.S. federal court.

Coast Guard Live Fire Exercises on the Great Lakes

In August of 2006 the United States Coast Guard published a notice in the Federal Register that they intended to designate 34 areas in U.S. portions of the Great Lakes at least five miles offshore as permanent safety zones for live fire machine gun practice. Each zone would be used by the Coast Guard for a maximum total of 24 hours a year and would be open to the public when not in use. In response to requests from the public, the Coast Guard is holding a series of public meetings in nine U.S. cities to solicit comment. The vast majority of people who showed up to voice concern about the plan and its impact on the environment. Several environmental organizations and government officials have voiced their opposition. A preliminary health risk assessment stated that the “proposed training will result in no elevated risks for a freshwater system such as the Great Lakes… or generic marine environments using ‘realistic worst case’ assumptions, and further investigation is not recommended. If typical rather than worst case assumptions were used the predicted risk would be even less.” The Coast Guard has established an information page about their proposal.


In the U.S. Congress, the Great Lakes Collaboration Implementation Act puts into practice priority recommendations of a $20 billion Great Lakes clean-up plan released in December as part of the Great Lakes Regional Collaboration , a planning process established by President Bush in 2004. A bipartisan group of U.S. legislators introduced the bill, including U.S. Sens. Mike DeWine (R-Ohio) and Carl Levin (D-Michigan) and Reps. Vern Ehlers (R-Grand Rapids) and Rahm Emanuel (D-Chicago). The Great Lakes Collaboration Implementation Act would:

•Stop the introduction and spread of aquatic invasive species by enacting a comprehensive national program. •Prevent the Asian carp from entering the Great Lakes by authorizing the Corps of Engineers to maintain and operate the dispersal barrier on the Chicago Sanitary and Ship Canal, and prohibit the importation and sale of Asian carp. •Restore fish and wildlife habitat by reauthorizing the Great Lakes Fish & Wildlife Restoration Act at $20 million. •Prevent sewage contamination by reauthorizing the State Revolving Loan Fund and provide $20 billion over five years to assist communities nationally with improving their wastewater infrastructure. •Clean up contaminated sediment under the Great Lakes Legacy Act by authorizing $150 million per year. •Phase out mercury in products by establishing a new grant program and improving existing research programs. •Coordinate and improve Great Lakes programs by establishing the Great Lakes Interagency Task Force and the Great Lakes Regional Collaboration process.

The Healing Our Waters(R) - Great Lakes Coalition has formed to help groups and citizens across the United States advocate for restoring the health of the Great Lakes.

Additions to the Five Great Lakes

Lake Champlain on the border between upstate New York and northwestern Vermont briefly became labelled by the U.S. government as the sixth "Great Lake of the United States" on March 6, 1998, when President Clinton signed Senate Bill 927. This bill, which reauthorized the National Sea Grant Program, contained a line penned by Senator Patrick Leahy (D-VT) declaring Lake Champlain to be a Great Lake. Not coincidentally, this status allows neighboring states to apply for additional federal research and education funds allocated to these national resources. The claim was viewed with some amusement by other countries, particularly in the Canadian media as many Canadians were originally unfamiliar with the lake's existence (despite its role in the War of 1812) and the lake is small compared to other Canadian lakes (such as Great Bear Lake which has over 27x more surface area). Following a small uproar (and several New York Times articles), the Great Lake status was rescinded on March 24 (although Vermont universities continue to receive funds to monitor and study the lake).

Similarly, there has been interest in making Lake St. Clair a Great Lake. In October, 2002, backers planned to present such a proposal at the Great Lakes Commission annual meeting, but ultimately withheld it as it appeared to them to have too little support.

Ecological challenges

Before the arrival of Europeans, the lakes provided fish to the native groups who lived near them. Early European settlers were astounded by both the variety and quantity of fish. Historically, fish populations were the early indicator of the condition of the Lakes, and have remained one of the key indicators even in our technological 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 (147 million pounds)," though the beginning of environmental impacts on the fish can be traced back nearly a century prior to those years.

By 1801, New York legislators 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 nineteenth century, Upper Canada’s government 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 and often quite spotty.

On both sides of the U.S.-Canada border, the proliferation of dams and impoundments multiplied, necessitating more regulatory efforts. The decline in fish populations was unmistakable by the middle of the nineteenth century. The decline in salmon was recognized by Canadian officials and reported as virtually a complete absence by the end of the 1860s. The Wisconsin Fisheries Commission noted a reduction of roughly 25 percent in general fish harvests by 1875.

Overfishing was cited as responsible for the decline of the 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). Recorded sturgeon catches fell from 7.8 million pounds (1.5 million kg) in 1879 to 1.7 million pounds (770,000 kg) in 1899.

There were, however, other factors in the declines besides overfishing and the problems posed by dams and other obstructions. Logging in the region removed tree cover near stream channels which provide spawning grounds, and this affected necessary shade and temperature-moderating conditions. Removal of tree cover also destabilized soil, allowing soil to be carried in greater quantity into the streambeds, and even brought about more frequent flooding. Running cut logs down the Lakes’ tributary rivers also stirred bottom sediments. In 1884, the New York Fish Commission determined that the dumping of sawmill waste (chips and sawdust) was impacting fish populations.

The Great Lakes are international, and in situations that require regulation, a lack of cooperation between the U.S. and Canada might be predicted to have disastrous consequences. In the development of ecological problems in the Great Lakes, it was the influx of parasitic lamprey populations after the development of the Erie Canal and the much later Welland Canal that led to the two federal governments attempting to work together – which proved a very complicated and troubled road.

Nevertheless, despite the ever more sophisticated efforts to eliminate or minimize the lamprey, by the mid 1950s Lake Michigan and Huron’s lake trout populations were reduced by about 99%, with the lamprey deemed largely to blame. A result was the bi-national Great Lakes Fishery Commission.

Other ecological problems in the Lakes and their surroundings have stemmed from urban sprawl, sewage disposal, and toxic industrial effluent. These, of course, also affect aquatic food chains and fish populations. Some of these glaring problem areas are what attracted the high-level publicity of Great Lakes ecological troubles in the 1960s and 1970s. Evidence of chemical pollution in the Lakes and their tributaries now stretches back for decades. In the late 1960s, the recurrent phenomenon of the surface of river stretches (see Ohio’s Cuyahoga River) catching fire from a combination of oil, chemicals, and combustible materials floating on the water’s surface, came to the attention of a public growing more environmentally aware. Another aspect that caught popular attention was the “toxic blobs” (expanses of lake bed covered by various combinations of such substances as solvents, wood preservatives, coal tar, and metals) found in Lake Superior, the St. Clair River, and other portions of the Great Lakes region.

According to the authoritative bi-national source The Great Lakes: An Environmental Atlas and Resource Book, "Only pockets remain of the once large commercial fishery."

The annual Great Lakes Bioneers Conference held in Traverse City, Michigan addresses many of these problems with local speakers, workshops and tools. The conference is a satellite conference of the Bioneer Conference in San Rafael, California. The Traverse City site focuses on durable ecological and socially just solutions to a diverse set of issues in the Great Lakes bioregion.


The names of the five Great Lakes are often remembered with the mnemonic HOMES, from the first letter of the name of each lake.

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