Difference between revisions of "Great Lakes" - New World Encyclopedia

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[[image:Great Lakes from space.jpg|thumb|400px|right|The Great Lakes from space]]
 
[[image:Great Lakes from space.jpg|thumb|400px|right|The Great Lakes from space]]
  

Revision as of 00:08, 5 August 2007


The Great Lakes from space

The Great Lakes of the Laurentian Shield 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.

Lakes


The Great Lakes are:

  • Lake Superior (the largest by volume, area, and depth; 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 most shallow of all the great lakes)
  • 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

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.

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. 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 divide Lake Huron into the lake proper and Georgian Bay.

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, the international border for part 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

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 (also 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 (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: 5,472 cubic miles (22,812 km³), or 6 quadrillion U.S. gallons (22.81 quadrillion liters) 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 or the provinces of Prince Edward Island and Newfoundland and Labrador combined.

The Great Lakes' coast measures 10,900 miles (17,549 km) (including islands and connecting channels), nearly as long as the total US ocean coastline (12,383 miles or 19,928 km), including Alaska.

The Saint Lawrence Seaway and Great Lakes Waterway connect the Great Lakes to ocean-going vessels. However the trend 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 halts during that season. Some icebreakers operate on the lakes.

The lakes affect weather in the region, a phenomenon known as lake effect. In winter, the moisture picked up by the prevailing winds from the west can produce very heavy snowfall, especially along eastern lakeshores in 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 also 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 in the form of fog, particularly along the shorelines of those lakes. This is most noticeable along Lake Superior's shores, due to its maritime climate.

The Great Lakes have been known to 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. In 1996, a rare subtropical cyclone formed in Lake Huron, dubbed the 1996 Lake Huron cyclone.

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.

Geological 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".

Economy

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 created 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. These immigration routes still have an effect today. Immigrants often formed their own communities and some areas have a pronounced ethnicity, predominantly Dutch, German, Polish, Finnish, among others.

Since general freight these days is transported by railroads and trucks, domestic ships mostly move bulk cargoes, like 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 raw materials for steel to centralized plants rather than forge steel at the mine sites. Components for steel, however, are not the only bulk shipments; 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 developed largely 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. Ocean-going vessels are known as salties.

One of the more common sights on the lakes is the 1,000 by 305 foot (105 by 32 meter), 60,000 US 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 increased 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 starting in 1697 with the brigantine Le Griffon. Commissioned by René Robert Cavelier, Sieur de La Salle,the ship 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.

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 are too wide to pass through the locks on the Saint Lawrence Seaway. The total amount of shipping on the lakes has been on a downward trend for several years.

File:Carlb-lake-Ontario-02.jpg
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 bordering 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 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 crossing Lake Ontario from Rochester, New York to Toronto ran during 2004 and 2005, but is no longer in operation.

Shipwrecks

Travel on the Lakes has been risky. Because of the immense size of the Lakes, there are vast stretches of open water without sight of land. The Lakes are sometimes referred to as inland seas.

Many thousands of ships have sunk in these waters. Storms and unseen reefs are a frequent threat. An estimated 6,000 to 10,000 ships have sunk or been stranded since the early 1800s, many with partial or total loss of crew. The Lakes are prone to sudden and severe storms, particularly in the autumn, from late October until early December. The Great Lakes Storm of 1913 is 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 the last major freighter lost on the lakes, sinking almost 20 miles off Whitefish Point in Lake Superior with all 29 crew members lost.

The greatest concentration of these wrecks lies near Thunder Bay (Michigan), in 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.

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.

Invasive species

The Great Lakes have suffered from the introduction of many non-native species. Since the 1800s, more than 300 invasive or non-native 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 non-indigenous 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." [1] http://www.cbc.ca/technology/story/2007/06/11/science-invasive-epa.html

Zebra mussel infestations in the Great Lakes and inland waters illustrate the severity of the problems stemming from invasive species introduction and spread. This non-indigenous 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, expend 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 US$5 billion dollars over the next decade. [2]

Approximately 10 percent of non-indigenous aquatic species introduced into the Great Lakes have had significant economic and ecological impacts. 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 consumes flesh and fluid from its prey, resulting in substantial economic losses to recreational and commercial fisheries. Control of sea lamprey predation requires annual expenditures of millions of dollars. ref: www.protectyourwaters.net/impacts.php#f

Alewife, introduced through Great Lakes canal systems, litter beaches each spring and alter food webs, causing increased water turbidity. These impacts have subsided with the 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. [3]

A more recent threat to Lake Michigan fisheries is viral hemorrhagic septicemia, an introduced pathogen that can survive up to fourteen days in lake water, infecting any fish that come in contact with it.

An electric fence has been set up across the mouth of the Chicago Sanitary and Ship Canal in order to keep several invasive species of Asian carp out of Lake Michigan. The carp have voracious appetites and feed upon native fish species. They can grow to 90 pounds (kg) and nearly four feet (12 m) long. [4]. The barrier is not in use at this time as issues of controlling the electric current in the canal are not yet resolved.

At least 30% of all invasive species were introduced into the Great Lakes in ballast water of cargo and other ships. The US Coast Guard has instituted rules requiring the exchange of ballast water or sealing of ballast tanks on all ship traffic in the Lakes. Legislation requiring the management of ballast water was enacted in 2004, replacing the voluntary management legislation passed earlier in 1996. <Cite error: Invalid <ref> tag; invalid names, e.g. too many and <reference /> tags


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Sources and Further Reading

  • Shear, Harvey, Kent Fuller, and Jennifer Wittig. 1995. The Great Lakes: an environmental atlas and resource book. Toronto: Govt. of Canada. ISBN 0662234413 and ISBN 9780662234418
  • Dempsey, Dave. 2004. On the brink: the Great Lakes in the 21st century. East Lansing: Michigan State University Press. ISBN 0870137050 and ISBN 9780870137051

External Links

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North American Great Lakes
Lake Superior | Lake Michigan | Lake Huron | Lake Erie | Lake Ontario

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Coordinates: 45° N 84° W

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