The Great Lakes are a collection of freshwater lakes located in eastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by surface. They are sometimes referred to as the North Coast or "Third Coast" by some citizens of the United States. Because of their size, types of ecosystems, and large abundances of beaches and coastal wetlands along their coasts, some regard them as inland seas or as one sea.
The Great Lakes hold 20% of the world's fresh water.
The Great Lakes region contains not only the five main lakes themselves, but also numerous minor lakes and rivers, as well as approximately 35,000 islands.
|Lake Erie||Lake Huron||Lake Michigan||Lake Ontario||Lake Superior|
|Surface area||9,940 sq mi (25,700 km2)||23,010 sq mi (59,600 km2)||22,400 sq mi (58,000 km2)||7,540 sq mi (19,500 km2)||31,820 sq mi (82,400 km2)|
|Water volume||116 cu mi (480 km3)||849 cu mi (3,540 km3)||1,180 cu mi (4,900 km3)||393 cu mi (1,640 km3)||2,900 cu mi (12,000 km3)|
|Elevation||571 ft (174 m)||577 ft (176 m)||577 ft (176 m)||246 ft (75 m)||600 ft (180 m)|
|Average depth||62 ft (19 m)||195 ft (59 m)||279 ft (85 m)||283 ft (86 m)||483 ft (147 m)|
|Maximum depth||210 ft (64 m)||770 ft (230 m)||923 ft (281 m)||808 ft (246 m)||1,332 ft (406 m)|
|Major settlements||Buffalo, NY
Owen Sound, ON
Port Huron, MI
Bay City, MI
Michigan City, IN
Green Bay, WI
Sault Ste. Marie, ON
Sault Ste. Marie, MI
Thunder Bay, ON
|Notes:||The area of each rectangle is proportionate to the volume of each lake. All measurements at Low Water Datum.|
Lakes Michigan and Huron are hydrologically a single lake, sometimes called Lake Michigan-Huron; they have the same surface elevation of 577 feet (176 m), and are connected not by a river but by the 295-foot (90 m) deep Straits of Mackinac.
Dispersed throughout the Great Lakes are approximately 35,000 islands. The largest among them is Manitoulin Island in Lake Huron, the largest island in any inland body of water in the world. The second-largest island is Isle Royale in Lake Superior. Both of these islands are large enough to contain multiple lakes themselves — Manitoulin Island's Lake Manitou is listed in the Guinness Book of World Records as the world's largest lake located on a freshwater island.
The Saint Lawrence Seaway and Great Lakes Waterway opened the Great Lakes to ocean-going vessels. 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, interrupting most shipping. Some icebreakers ply the lakes.
The Great Lakes are also connected to the Gulf of Mexico by way of the Illinois River (from Chicago) and the Mississippi River. An alternate track is via the Illinois River (from Chicago), to the Mississippi, up the Ohio, and then through the Tennessee-Tombigbee Waterway (combination of a series of rivers and lakes and canals), to Mobile Bay and the Gulf. Commercial tug-and-barge traffic on these waterways is heavy.
Pleasure boats can also enter or exit the Great Lakes by way of the Erie Canal and Hudson River in New York. The Erie Canal connects to the Great Lakes at the east end of Lake Erie (at Buffalo, NY) and at the south side of Lake Ontario (at Oswego, NY).
The lakes are bound by the Canadian province of Ontario and the U.S. states of Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York. However, not all of the lakes border on all of these regions. Four of the five lakes form part of the Canada-United States border; the fifth, Lake Michigan, is contained entirely within the United States. The Saint Lawrence River, which marks the same international border for a portion of its course, is the primary outlet of these interconnected lakes, and flows through Quebec and past the Gaspé Peninsula to the northern Atlantic Ocean.
|Lake Erie||Lake Huron||Lake Michigan||Lake Ontario||Lake Superior|
|Origins of Name||Erie (tribe); shorten form of Iroquoian word Erielhonan or “long tail”||Named by French explorers for inhabitants in the area, Wyandot or “Hurons”||Likely from the Ojibwa word mishigami meaning “great water”||Wyandot (Huron) word ontarío meaning “Lake of Shining Waters” (Ontara = beautiful, Ontario = beautiful lake)||English translation of French term “lac supérieur” ("upper lake"), referring to its position above Lake Huron, Ojibwe called it "Gitchigumi"|
The Great Lakes contain roughly 22% of the world’s fresh surface water: 5,472 cubic miles (22,810 km3), or 6.0×1015 U.S. gallons (2.3×1016 liters). This is enough water to cover the 48 contiguous U.S. states to a uniform depth of 9.5 feet (2.9 m). However, only 2% of this volume is replaced each year, causing water levels to fall in recent years as the water undergoes heavy human use. Although the lakes contain a large percent of the world's fresh water, the Great Lakes supply only a small portion of America's drinking water (roughly 4.2%).
The combined surface area of the lakes is approximately 94,250 square miles (244,100 km2)—nearly the same size as the United Kingdom, and larger than the U.S. states of New York, New Jersey, Connecticut, Rhode Island, Massachusetts, Vermont and New Hampshire combined.
The Great Lakes coast measures approximately 10,500 miles (16,900 km); however, the length of a coastline is impossible to measure exactly and is not a well-defined measure (see Coastline paradox).
It has been estimated that the foundational geology which created the conditions shaping the present day upper Great Lakes was laid from 1.1 to 1.2 billion years ago, when two previously fused tectonic plates split apart and created the Midcontinent Rift. A valley was formed providing a basin that eventually became modern day Lake Superior. When a second fault line, the Saint Lawrence rift, formed approximately 570 million years ago, the basis for Lakes Ontario and Erie were created, along with what would become the St. Lawrence River.
The Great Lakes are estimated to have been formed at the end of the last ice age (about 10,000 years ago), when the Laurentide ice sheet receded. The retreat of the ice sheet 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. Land below the glaciers "rebounded" as it was uncovered. Because the glaciers covered some areas longer than others, this glacial rebound occurred at different rates. Some researchers believe that differential has contributed to fluctuating water levels throughout the Great Lakes basin.
The effect of Great Lakes on weather in the region is called the lake effect. In winter, the moisture picked up by the prevailing winds from the west can produce very heavy snowfall, especially along lake shores to the east such as Michigan, Ohio, Pennsylvania, Ontario, and New York. 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. Western Michigan has apple and cherry orchards, and vineyards adjacent to the lake shore as far north as the Grand Traverse Bay. The eastern shore of Lake Michigan and the southern shore of Lake Erie have many wineries as a result of this, as does 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, Ontario on Lake Ontario's northeast shore. 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 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 warmth 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 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, and became the first sailing ship to travel the upper Great Lakes on August 7, 1679.
During settlement, the Great Lakes and its rivers were the only practical means of moving people and freight. 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, except for ferries and a few foreign cruise ships, has now vanished.
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, 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 cargo 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, 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 some distinctive vocabulary. Ships, no matter the size, are called 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 (see Lake freighter). 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-long-ton (80,120-metric-ton) self-unloader. This is a laker with a 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 increased use of overland freight, and a few larger ships replacing many small ones.
The Great Lakes are today used as a major mode of transport for bulk goods. In 2002, 162 million net tons of dry bulk cargo were moved on the Lakes. This was, in order of volume: iron ore, grain, 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 the ships are too wide. The total amount of shipping on the lakes has been on a downward trend for several years.
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.
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. In addition, all kinds of water sports can be found on the lakes. Unusually for inland waters, the Great Lakes provide the possibility of surfing, particularly in winter due to the effect of strong storms and waves.
From 1844 through 1857, palace steamers carried passengers and cargo around the Great Lakes. Throughout the 20th century, large luxurious passenger steamers sailed from Chicago all the way to Detroit and Cleveland. These were primarily operated by the Detroit & Cleveland Navigation Company. 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, three car ferry services cross the Great Lakes, two on Lake Michigan: a steamer from Ludington, Michigan to Manitowoc, Wisconsin and a high speed catamaran from Milwaukee to Muskegon, Michigan, and one on Lake Erie: a boat from Kingsville, Ontario, or Leamington, Ontario to Pelee Island, Ontario then onto Sandusky, Ohio. An international ferry across Lake Ontario from Rochester, New York to Toronto ran during 2004 and 2005, but is no longer in operation.
|Ship's Name||Year Built||Nationality||Ship's Name||Year Built||Nationality||Ship's Name||Year Built||Nationality|
|Niagara||1856||United States||SS Christopher Columbus||1892||United States||SS Eastland||1902||United States|
|Milwaukee Clipper||1904||United States||SS Keewatin||1907||Canadian||Comet (steamboat)||1857||United States|
The large size of the Great Lakes increases the risk of water travel; storms and reefs are common threats. The lakes are prone to sudden and severe storms, particularly in the autumn, from late October until early December. Hundreds of ships have met their end on the lakes. The greatest concentration of shipwrecks lies near Thunder Bay (Michigan), beneath Lake Huron, near the point where eastbound and westbound shipping lanes converge.
The Lake Superior shipwreck coast from Grand Marais, Michigan to Whitefish Point became known as the "Graveyard of the Great Lakes". More vessels have been lost in the Whitefish Point area than any other part of Lake Superior. The Whitefish Point Underwater Preserve serves as an underwater museum to protect the many shipwrecks in this area.
The first shipwreck was the Griffin, the first ship to sail the Great Lakes. Caught in a storm while trading furs between Green Bay and Michilimacinac, it sank during a storm and has possibly been found. The last major freighter wrecked on the lakes was the SS Edmund Fitzgerald, which sank on November 10, 1975, just over 30 miles (50 km) offshore from Whitefish Point. The largest loss of life in a shipwreck out on the lakes may have been that of the Lady Elgin, wrecked in 1860 with the loss of around 400 lives. In an incident at a Chicago dock in 1915, the SS Eastland rolled over while loading passengers, killing 841.
In August 2007, the Great Lakes Shipwreck Historical Society announced that it had found the wreckage of Cyprus, a 420-foot (130 m) long, century-old ore carrier. Cyprus sank during a Lake Superior storm on October 11, 1907, during its second voyage while hauling iron ore from Superior, Wisconsin, to Buffalo, New York. The entire crew of 23 drowned, except one, a man named Charles Pitz, who floated on a life raft for almost seven hours.
In June 2008 deep sea divers in Lake Ontario found the wreck of the 1780 Royal Navy warship HMS Ontario in what has been described as an "archaeological miracle". There are no plans to raise her as the site is being treated as a war grave.
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 through the Great Lakes Commission, 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 of which is between all ten jurisdictions. It is somewhat more detailed and protective, though its legal strength has not yet been tested in court. The second, the Great Lakes Compact, has been approved by the state legislatures of all eight states that border the Great Lakes as well as the U.S. Congress, and was signed into law by President George W. Bush on 3 October 2008.
In 2006, the United States Coast Guard (USCG) proposed a plan to designate 34 areas in the Great Lakes, at least five miles (8 km) offshore, as permanent safety zones for live fire machine gun practice. In August 2006 the plan was published 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. 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.
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." However, the assessment was based on lead levels after five years, and so one could infer that lead levels could meet or exceed EPA safe levels for lead after fifteen years. The Coast Guard established an information page about their proposal at http://www.uscgd9safetyzones.com
On December 18, 2006, the Coast Guard announced its decision to withdraw the entire proposal. Officials said they would look into alternative ammunition, modifying the proposed zones and have more public dialogue before proposing a new plan.
During the 109th United States Congress in 2006, the Great Lakes Collaboration Implementation Act (Bill HR5100) was introduced to enact the recommendations of the Great Lakes Regional Collaboration, an effort established in 2004 to produce a strategy for restoring and maintaining the Great Lakes. The bill was introduced by U.S. senators Mike DeWine and Carl Levin, along with representatives Vern Ehlers and Rahm Emanuel.
The bill states that "the Great Lakes are on the brink of an ecologic catastrophe" and that "if the pattern of deterioration is not reversed immediately, the damage could be irreparable". It cites the closing of over 1,800 beaches in 2003, the 6,300-square-mile (16,300 km2) dead zone in Lake Erie, and the US$500 million damage each year due to the zebra mussel as evidences that "a comprehensive restoration of the system is needed to prevent the Great Lakes from collapsing".
A press release states that the bill aims to stop the introduction and spreading of invasive species, prevent the Asian carp from invading the Great Lakes, phase out mercury, restore animal habitats, and prevent sewage contamination.
A coalition called Healing Our Waters, or HOW was formed by several environmental groups and foundations in 2005 to educate and assist citizens in advocating for the cleanup of the Great Lakes.
Lake Champlain, a lake on the border between upstate New York and northwestern Vermont that is part of the Saint Lawrence-Great Lakes Watershed, 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 and Time Magazine articles), the Great Lake status was rescinded on March 24, 1998 (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.
The ecological history of the Great Lakes includes both great losses and enormous recovery; the system today is in the most obvious ways much healthier than it was a half-century ago, while in less apparent ways it remains seriously compromised.
Before the arrival of Europeans, the Great Lakes provided fish to the indigenous groups who lived near them. Early European settlers were astounded by both the variety and quantity of fishes; there were 150 different species in the Great Lakes. Historically, fish populations were the early indicator of the condition of the Lakes, and have remained one of the key indicators even in the current era of sophisticated analyses and measuring instruments. According to the bi-national (U.S. and Canadian) resource book, The Great Lakes: An Environmental Atlas and Resource Book, "the largest Great Lakes fish harvests were recorded in 1889 and 1899 at some 67,000 tonnes [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 19th 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 Canada–United States border, the proliferation of dams and impoundments multiplied, necessitating more regulatory efforts. The decline in fish populations was unmistakable by the middle of the 19th century, as the obstructions in the rivers prevented salmon and sturgeon from reaching their spawning grounds. 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. 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 one 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. The population of giant freshwater mussels was eliminated as the mussels were harvested for use as buttons by early Great Lakes entrepreneurs.
There were other factors in the population declines besides overfishing and the problems posed by water obstructions. Logging in the Great Lakes region removed tree cover near stream channels which provide spawning grounds; 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.
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. Despite a variety of efforts to eliminate or minimize the lamprey, by the mid-1950s the lake trout populations of Lakes Michigan and Huron were reduced by about 99%, with the lamprey deemed largely to blame. This led to the launch of the bi-national Great Lakes Fishery Commission.
Other ecological problems in the Lakes and their surroundings have stemmed from urban runoff and 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 stretch back for decades. In the 1960s Ohio’s Cuyahoga River (or more precisely a combination of oil, chemicals and trash floating atop it in Cleveland) ignited and smoldered, creating international headlines.
The Cuyahoga, and a TIME Magazine cover story about the "death" of Lake Erie, helped focus public and policymaker attention and inspire the first Earth Day events in 1970. New advocacy organizations such as the Lake Michigan Federation, founded in 1970 by Lee Botts, brought new public pressure to bear. The first U.S. Clean Water Act, signed by Pres. Richard Nixon in 1972, was a key step forward as was the innovative bi-national Great Lakes Water Quality Agreement signed by Canada and the U.S. Thanks to a variety of steps taken to reduce industrial and municipal pollution discharges into the system, basic water quality had by the 1980s improved sharply and Lake Erie in particular was significantly healthier. The ongoing discharge of toxic substances has also been sharply reduced thanks to federal and state bans of substances like PCBs and DDT, though historic toxics remain embedded in harbor and rivermouth sediments in dozens of "Great Lakes Areas of Concern".
The authoritative but now outdated 1972 book The Great Lakes: An Environmental Atlas and Resource Book noted that "only pockets remain of the once large commercial fishery." In the meanwhile however the great water quality improvements realized during the 1970s and 1980s, combined with successful salmonid stocking programs, have enabled the growth of a large recreational fishery.
Since the 1800s an estimated 160 species have invaded the Great Lakes ecosystem, with ship ballast being a primary suspected pathway, causing severe economic and ecological impacts. According to the Inland Seas Education Association, on average a new invasive species enters the Great Lakes every eight months.
One such infestation in the Great Lakes was the introduction of the zebra mussel, which was first discovered in 1988. The mollusk is an efficient feeder, competing with native mussels. It also reduces available food and spawning grounds for fish. The zebra mussel also hurts utility and manufacturing industries by clogging or blocking pipes. The U.S. Fish and Wildlife Service estimates that the economic impact of the zebra mussel will be about $5 billion over the next decade.
The alewife first entered the system west of Lake Ontario via 19th-century canals. By the 1960s the small silver fish had become a familiar nuisance to beachgoers across Lakes Michigan, Huron and Erie as periodic mass dieoffs resulted in vast numbers of them washing up on shore; estimates by various governments have placed the percentage of Lake Michigan's biomass which was made up of alewives in the early 1960s as high as 90 percent. The various state and federal governments began stocking several species of salmonids in the late 1960s, including the native lake trout as well as non-native chinook and coho salmon; by the 1980s alewife populations had dropped drastically. Ironically, today the sharply-lower numbers of alewives is seen as a problem  by those involved in the large recreational fishing sector that has grown up particularly on Lake Michigan.
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 fish, overruns optimal habitat, spawns multiple times a season and can survive poor water quality conditions.
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. More recently an electric fence has been set up 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 fish have heavily colonized the Mississippi and Illinois river systems. 
It has been suggested that invasive species, particularly zebra and quagga mussels, may be at least partially responsible for the collapse of the deepwater demersal fish community in Lake Huron, as well as drastic unprecedented changes in the zooplankton community of the lake.
The Great Lakes are an important water system of North America for transportation, commerce, and recreation. Lying on the border between the United States of America and Canada, they are the largest bodies of fresh water in the world making them an invaluable natural resource. The size is difficult to appreciate until you see them: at 94,250 square miles (244,100 km2) combined, the lakes are nearly as large as the United Kingdom, and a plane flying over one will not see land on any side.
Although lakes usually have names like "This Lake" and "That Lake", the Great Lakes are named the other way 'round as "Lake This" and "Lake That". In this area, if someone says something like "lets go to the Lake" without naming it, they're probably referring to the nearest Great one.
The following regions lie around the Great Lakes.
The following cities lie on or close to the shores of the Great Lakes.
Many boaters utilize the Great Lakes, St. Lawrence Seaway and their connection points as a travel route. There are many marinas and public boat ramps available for this purpose. Also, the Great Lakes Cruising Company and the American Canadian Caribbean Line provide cruises on the Great Lakes.
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The lakes are:
Water flows from Lake Superior and Lake Michigan into Lake Huron; then through the Detroit River into Lake Erie; then through Niagara Falls into Lake Ontario; and then through the Saint Lawrence River to the Atlantic Ocean.
|North American Great Lakes|
|Lake Superior - Lake Michigan - Lake Huron - Lake Erie - Lake Ontario|