Introduction
The Great Lakes consist of five lakes in North America, on the border between the United States and Canada. Lake Erie, Lake Ontario, Lake Huron, Lake Michigan and Lake Superior make up the greatest area of freshwater in the world. The five lakes have an area of about 100,000 square miles (250 000 square kilometres). Only one of them, Lake Michigan lies completely in the United States, the others form a natural border between the United States and Canada.
The St. Lawrence Seaway, opened in 1959, connects the Great Lakes with the Atlantic Ocean, making it possible for cargo vessels to travel all the way to Chicago, more than a thousand miles from the coast. The lakes are also connected through a series of rivers and canals with the Mississippi River and the Gulf of Mexico.
The Great Lakes are not all at the same sea level. Lake Superior lies at an elevation of 183 meters, while Lake Ontario lies lowest, at 74 meters above sea level. Niagara Falls, between Lake Erie and Lake Ontario, causes a drop of a hundred meters. A system of locks and canals makes it possible for ships to travel between the Lakes. During the winter months, large parts of the Great Lakes freeze but icebreakers keep shipping lanes open most of the time.
The Great Lakes
Image : Phizzy at the English Wikipedia, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/,
via Wikimedia Commons
St. Lawrence Seaway
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Niagara Falls
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via Wikimedia Commons
How the Great Lakes Were Formed
The basin of today’s lakes was formed about 2 billion years ago through volcanic activity. Recently the glaciers of the Ice Age repeatedly advanced and retreated throughout the region. They pushed rocks and other material with them and dug out a huge depression which filled itself with melting water after the last withdrawal of the glaciers, about 20,000 years ago. Together with the five Great Lakes thousands of other, smaller lakes were formed.
The Great Lakes gets most of their water from rain and snow throughout the year. Groundwater makes up most of the rest because there are only few large rivers flowing into the lakes. Due to global warming water levels have been going down in recent years.
The Great Lakes during the Ice Age
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Public Domain
Economic Importance of the Great Lakes
The Great Lakes have contributed very much to the economic development of the United States and Canada. Millions of tons of raw material, including ore and coal, as well as industrial goods are transported along the Great Lakes every year. About 70% of all the iron ore of the United States is mined near Lake Superior. Large freighters bring it to all parts of the world.
Much of the coal produced in the Appalachian coal fields are brought to the Great Lakes by train where they are loaded onto cargo ships and exported to other areas.
Farming crops of the American Midwest, including corn and wheat are brought to the harbours along the Great Lakes where they are exported to other countries.
Because water transport is very cheap, farmers in the American Midwest and Canada can compete with their rivals in other continents.
Cargo ship on St. Lawrence Seaway
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Recreation and Tourism
Millions of Americans spend much of their free time on and around the Great Lakes. Residents of Chicago, Detroit, Cleveland, Milwaukee and other big cities flock to the beaches to escape the stressful life of the inner cities. Sailing and other water sports are widespread due to strong winds that prevail in the Great Lakes region. Fishing is a main source of income for many people in the area.
Beach in Chicago
Image: Chris6d, CC BY-SA 4.0, via Wikimedia Commons
Sailing on Lake Ontario
Image: Larry Koester, CC BY 2.0, via Wikimedia Commons
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History of the Great Lakes
The first settlers sailed down the Great Lakes about 300 years ago. In those days they were mainly fur traders who made business with Indians. The first canals in the 19th century made it possible to travel from lake to lake.
During the course of the 20th century the water quality of the Great Lakes deteriorated, largely because of pollution by cargo vessels and industries along its shores. Recently the United States and Canady have been spending millions every year to raise the quality of the world’s largest freshwater region.