This article is about the group of North American lakes. For the African lakes, see African Great Lakes. For other uses of this term, see Great Lakes (disambiguation).
The Laurentian 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 freshwater lakes on Earth. The Great Lakes–St. Lawrence system is the largest freshwater system in the world. They are sometimes referred to as inland seas. (See also: Third Coast.)

The Great Lakes
Lakes:
Rivers: 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.
Connections: Lake Michigan is connected to Lake Huron through the Straits of Mackinac. Large islands and a peninsula divide Lake Huron into the lake proper and Georgian Bay.

Lake St. Clair, a much smaller lake, is part of the Great Lakes system between Lake Huron and Lake Erie, but is not considered one of the Great Lakes.
Lake Nipigon is another large lake that is part of the same hydrological system, but not part of the Great Lakes proper.
Other lakes of notable mention that are not considered part of the Great Lakes, but are part of their hydrological system, are Lake Nipissing, Lake Simcoe, Lake Winnebago, Oneida Lake, the Finger Lakes of Upstate New York, and Lake Champlain. Other waters
The lakes are bounded by Ontario (all of the lakes except Michigan), Minnesota, Wisconsin, Michigan (all but Lake 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.

Boundaries
Sprinkled throughout the lakes are approximately 35,000 islands, including Manitoulin Island in Lake Huron—the largest island in any inland body of water and home to the world's largest lake within a lake, Lake Manitou—and Isle Royale in Lake Superior, the largest island in the largest lake (both of these islands are large enough to contain multiple lakes themselves).

Islands
The Great Lakes contain 20% of the world's fresh surface water: 5,472 cubic miles (22,812 km³), or 6.0 × 10 L). It is enough water to cover the contiguous 48 U.S. 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, or the Canadian province of Prince Edward Island.
The Great Lakes coast measures 10,900 miles (17,549 km) (including islands and connecting channels), nearly as long as the total U.S. ocean coastline (19,928 km, or 12,383 mi), except Alaska and the two shorelines along the approximately 12,000 miles (19,000 km) of channel that constitute the commercially active inland and intracoastal waterway system maintained by the U.S. Army Corps of Engineers.

Statistics
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. Some icebreakers operate on the lakes.

Connection to ocean and open water
The effect the Great Lakes have on weather in the region is known as the 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 Michigan, Ohio, Pennsylvania, 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. The eastern shore of Lake Michigan and the southern shore of Lake Erie are home to many wineries as a result of this, as is the Niagara Peninsula between Lake Erie and Lake Ontario. A similar phenomenon occurs in the Finger Lakes region of New York as well as Prince Edward county on the northeast shore of Lake Ontario. Related to lake effect, is the occurrence of fog over medium-sized areas, particularly along the shorelines of the lakes. This is most noticeable along Lake Superior's shores, due to its maritime climate.
The Great Lakes have also been observed to help strengthen storms, such as Hurricane Hazel in 1954, and a frontal system in 2007 that spawned a few tornadoes in Michigan and Ontario, picking up the warmth and energy from the lakes to fuel them. Also observed in 1996, was a rare subtropical cyclone forming in Lake Huron, dubbed the 1996 Lake Huron cyclone.


The lake effect
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.

Geological pre-history
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, 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 were 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), 78,850 UK long ton (80,117 metric tonne) self-unloader. This is a laker with a huge conveyor belt system that can unload itself by swinging a crane over the side.[1] Today, the Great Lakes fleet is much smaller in numbers than it once was because of the increased use of overland freight and the use of larger ships replacing the need for many smaller ships.

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 were 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.
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.

Modern economy
From 1844 through 1857, palace steamers carried passengers and cargo around the Great Lakes. Several ferries currently 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 2007, two car ferry services cross the Great Lakes, both on Lake Michigan: a steamer from Ludington, Michigan to Manitowoc, Wisconsin and a high speed catamaran from Milwaukee to Muskegon, Michigan. An international ferry across Lake Ontario from Rochester, New York to Toronto ran during 2004 and 2005, but is no longer in operation.

Passenger traffic
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. She sank just over 30 miles offshore from Whitefish Point in Lake Superior. 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, 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.
Cyprus
In August 2007, Tom Farnquist (executive director of the Great Lakes Shipwreck Historical Society) said it had found the wreckage (460 feet beneath the surface) of Cyprus—a 420-foot-long, century-old ore carrier which sank during a Lake Superior storm. All but Charles G. Pitz of the Cyprus' crew of 23 perished on October 11, 1907. The ship sank in Lake Superior during its second voyage while hauling iron ore from Superior, Wisconsin, to Buffalo, New York. Built in Lorain, Ohio, the Cyprus was launched August 17, 1907.

Shipwrecks
The Great Lakes have suffered from the introduction of many non-native species. Since the 1800s, more than 160 invasive species have invaded the Great Lakes ecosystem from around the world, causing severe economic and ecological impacts. Other terms used to describe invasive species include nonindigenous, aquatic nuisance species (ANS), and aquatic pests.
"Over 160 invasive species threaten the ecological balance of the Lakes. They deprive fish of food, cause blooms of toxic algae, and foul boats, spawning areas and drinking water intakes. On average one new invasive enters the Great Lakes every eight months." [2]
Zebra mussel infestations in the Great Lakes and inland waters illustrate the severity of the problems stemming from invasive species introduction and spread. This nonindigenous mollusk is an efficient filter feeder that competes with native mussels and impacts fish populations by reducing food and available spawning habitat. The utility and manufacturing industries around the region, depending on Great Lakes water for production, are expending substantial time and money cleaning intake and discharge pipes clogged by the zebra mussel. The U.S. Fish and Wildlife Service estimates the economic impact to these industries to be $5 billion dollars over the next decade. [3]
Approximately 10 percent of nonindigenous aquatic species introduced into the Great Lakes have had significant impacts, both economic and ecological. The remaining 90 percent have potentially harmful impacts but are insufficiently researched and understood. Besides the zebra mussel, several other species have been particularly harmful. The invasion of the sea lamprey, a parasite that attaches to large fishes with a sucker mouth armed with teeth that consume flesh and fluid from its prey, has resulted in substantial economic losses to recreational and commercial fisheries. Protection of the Great Lakes fishery (both native and nonindigenous species) from sea lamprey predation has required annual expenditures of millions of dollars to finance chemical control programs.
Alewife, introduced through the canal systems built in the Great Lakes, littered beaches each spring and altered food webs, causing increased water turbidity. These impacts subsided with the intentional introduction of salmonids that were stocked as predators to keep alewife populations under control. The ruffe, a small percid fish, became the most abundant fish species in Lake Superior's St. Louis River within five years of its detection in 1986. Its range, which has expanded to Lake Huron, poses a significant threat to the lower lake fishery. Five years after first being observed in the St. Clair River, the round goby can now be found in all of the Great Lakes. The goby is considered undesirable for several reasons: It preys upon bottom-feeding fishes, overruns optimal habitat, spawns multiple times a season, and can survive poor water quality conditions. [4]
Several species of water fleas have accidentally been introduced into the Great lakes such as Bythotrephes cederstroemi and the Fishhook waterflea potentially having an effect on the zooplankton population. Several species of crayfish have also been introduced that may contend with native crayfish populations
An electric fence has been set up across the mouth of the Great Lakes across the Chicago Sanitary and Ship Canal in order to keep several species of invasive Asian carps out of the area. These fast-growing planktivorous fishes are thought to have the potential to cause substantial ecological damage to the Great Lakes, through changes in the food chain and water quality. [5]

Invasive species

Political issues
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"[6], 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 [7] and the Great Lakes-St. Lawrence River Basin Water Resources Compact [8] 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 of which 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.

Great Lakes water use and diversions
In 2006, the United States Coast Guard had proposed a plan to designate 34 areas in U.S. portions of the Great Lakes including 14 in Lake Michigan, at least five miles offshore as permanent safety zones for live fire machine gun practice. The plan was published a notice in August, 2006 in the Federal Register. The USCG reserved the right to hold target practice whenever the weather allowed with a two hour notice. These firing ranges would be open to the public when not in use.[9] In response to requests from the public, the Coast Guard held a series of public meetings in nine U.S. cities to solicit comment. During these meetings many people voiced concerns about the plan and its impact on the environment.[10]
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… 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." This assessment is based on lead levels after 5 years which are only 1/3 of those allowed by the US EPA. After 15 years, one could infer, that lead levels could meet or exceed EPA safe levels for lead. [11] The Coast Guard established an information page about their proposal.[12]
On December 18, 2006, the Coast Guard announced its decision to withdraw the entire proposal. Officials said they will look into alternative ammunition, modifying the proposed zones and have more public dialogue before proposing a new plan. [13]
Restoration
Lake Champlain, on the border between upstate New York and northwestern Vermont, briefly became labeled 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, and the lake is small compared to other Canadian lakes (such as Great Bear Lake which has over 27 times 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.

Additions to the five Great Lakes
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, 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 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. These dams prevent sturgeon spawning, too. Many Michigan rivers sport multiple dams that range from mere relics to those with serious loss of life potential. The state's dam removal budget has been frozen in recent years. In the 1990s the state was removing 1 dam per year.
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. Giant Fresh water mussels were wiped out for buttons by early Great Lakes entrepreneurs.
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 Lakes Michigan's 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 Bioneers 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.

Trivia

Detroit River
Edmund Fitzgerald
Great Lakes Commission
Great Lakes Areas of Concern
International Boundary Waters Treaty
Lake Saint Clair (North America)
Lake surfing
List of cities along the Great Lakes
Michigan Underwater Preserves
Muskellunge
Northern Pike
Sixty Years' War for control of the Great Lakes