Great Lakes
Series of five freshwater lakes along the USA–Canadian border: Superior, Michigan, Huron, Erie, and Ontario; total area 245,000 sq km/94,600 sq mi. Interconnected by a network of canals and rivers, the lakes are navigable by large ships, and they are connected with the Atlantic Ocean via the St Lawrence River and by the St Lawrence Seaway (completed in 1959), which is navigable by medium-sized ocean-going ships.
Physical
The Great Lakes are said to contain 20% of the world's surface fresh water, and drain a basin of approximately 751,100 sq km/290,000 sq mi.
Industries
Nickel, copper, gold, silver, cobalt, arsenic, bismuth, and pitchblende are found to the north of Lakes Huron and Superior, and rich forest lands on their Canadian shores have given rise to a large wood-pulp industry. The
Niagara Falls are a valuable source of electric power both to the USA and to Canada. The lakes are ice-bound for some five months of the year, but are used for the rest of the year by bulk carriers known as ‘lakers’. The principal cargoes are iron ore and grain, both of which originate at Lake Superior ports. Iron ore is carried to other lake ports for transport to steel mills. Grain may be shipped to processing centres such as Buffalo, New York, or sent directly overseas.
Ports
The chief ports of the Great Lakes are Fort William, Port Arthur, Hamilton, Toronto, and Kingston in Canada; and Duluth, Chicago, Milwaukee, Detroit, Cleveland, Erie, Toledo, and Buffalo in the USA.
| Lake Superior (the largest in size and depth) is connected with Lake Huron via St Mary's River and by the Canadian and US ‘Soo’ (Sault Sainte Marie) canals. Huron (second largest in size, third in depth) flows into Lake Erie via the St Clair River, Lake St Clair, and the Detroit River. Michigan (third largest in size, second in depth) flows through the Straits of Mackinac into Lake Huron. Lake Erie flows into Lake Ontario through the Niagara River and is also connected with it via the Welland Ship Canal. The Illinois Waterway connects Lake Michigan at Chicago with the Mississippi River; and the New York State Barge Canal connects Lake Erie at Buffalo with the Hudson River and New York City. Exotic species of wildlife introduced to the Great Lakes have caused serious problems: sea lampreys, introduced in the early 20th century, are parasites to native fish, and zebra mussels, were introduced in 1988, have clogged water pipes and destroyed indigenous species. In a US study carried out in 1992–94 the lakes were found to be contaminated by the herbicide atrazine, widely used on surrounding land. There was estimated to be a total of 600 tonnes of atrazine in the lakes. The Great Lakes Charter regulates the use of water between the USA and Canada, and the Great Lakes Protection Fund (1989) attempts to improve the ecosystem. |
