Wednesday, October 28, 2009

North America

North America is the third largest continent, extending from the Arctic Ocean in the north to South America in the south. It covers about 24,249,000 sq km or about a'sixth 6f the world's land area, and extends between (approxi­mately) 84° N to 7° N latitudes and 180° W to 20° W longi­tudes.
The continent has four major physical divisions-the Canadian Shield, the Appalachian Mountains or Eastern Highlands, the Central Plains, and the Western Cordilleras. The Canadian Shield, a huge area of ancient rocks, covers most of Canada.

It is a reservoir of valuable mineral resources like gold, silver, nickel, iron, copper, platinum, radium, cobalt and uranium. A large part of the shield is made up of swamps and a number of lakes such as the Great Bear, Winnipeg and the Great Lakes (Lakes Superior, Michigan, Huron, Erie and Ontario). The famous Niagara Falls is located between Lake Erie and Lake Ontario.

The Appalachian Mountains, located in the north-east, are constituted of low rounded mountains, plateaus and valleys. A number of minerals are found here.
The Central Plains cover central Canada, mid-western United States and the coastal plains in Texas. The mid and southern parts are a vast low and flat river basin of the Missouri-Mississippi.

The Western Cordilleras are a mountainous region along the north to south of the western part of the continent. There are several parallel ranges. The Rocky mountains are North America's largest mountain range. The Alaska Range, the Coastal Range, the Sierra Nevada, the Cascade Range, etc., are the other ranges. Mt McKinley (6,194 m) in the Alaska Range is North America's highest mountain. Fertile valleys between the mountain ranges are major agricultural centres. The ranges also enclose inter­montane plateaus-the Great Basin is the largest in termon­tane plateau ot the continent. Most of the rivers of North America rise in the Western Cordilleras. There are many acttve volcanoes in the Western Cordilleras, especially in Alaska and Mexico.

The Mississippi-Missouri-Ohio is the continent's longest river system. The Grand Canyon of River Colorado is the largest of its kind in the world. Lake Superior is the largest freshwater lake in the world. Great Salt Lake in Utah is even saltier than the ocean. Most North American deserts lie in the southwestern United States and northern Mexico.

North America's coastline-about 300,000 km-is longer than that of any other continent. A number of countries lie off the coasts of the continent-Greenland (part of the North American continent, but governed as a province of Denmark), Newfoundland, Vancouver, the Aleutian Is­lands, and the West Indies.
North America experiences the most varied range of climate-from extremely dry cold of the Arctic type to the hot tropic.

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