Canada's landforms
From Wikipedia, the free encyclopedia
Canada is a land of great physical diversity. Perhaps this is not surprising since Canada is the second largest country in the world and has the world's longest coastline. We can evaluate Canada's topography by focusing on its landform regions and ecozones.
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[edit] Overview
Canada is made up of three distinct types of landforms- Shield, Highlands, and Lowlands. In total, Canada has seven distinct landform regions:
- The Canadian Shield
- The Innuitian Mountains
- The Arctic Lowlands
- The Hudson Bay Lowlands
- The Western Cordillera
- The Interior Plains
- The Great Lakes-St. Lawrence Lowland Landform Region
- The Appalachians
[edit] The Canadian Shield
The Canadian Shield— also called the Precambrian Shield, Laurentian Shield, or Laurentian Plateau— is a large thin soil covered area over a part of the North American craton (a deep, common, joined bedrock region) in eastern and central Canada and adjacent portions of the United States, composed of base rock dating to the Precambrian Era (between 4.5 billion and 540 million years ago). The Canadian Shield is almost circular which gives it an appearance of a warrior's shield or a giant horseshoe, and is a subsection of the Laurentia craton signifying the area of greatest glacial impact (scraping down to bare rock) creating fat soils.
Drainage is generally very poor on the shield, mostly due to the glaciation. The southern part of the shield has thick forests while the north is covered with tundra. The region is largely undeveloped but has great water-power potential and is a source of minerals, timber, and fur-bearing animals.
Regional Extent When the Greenland section is included, the Shield is approximately circular bounded on the northeast by the northeast edge of Greenland, with Hudson Bay in the middle. It covers much of Greenland; Labrador; most of Quebec north of the St. Lawrence River; much of Ontario outside the southern peninsula between the Great Lakes; the Adirondack Mountains of northern New York; parts of Michigan, Wisconsin, and Minnesota; the central portion of Manitoba away from Hudson Bay and the Great Plains; northern Saskatchewan; a small portion of north-eastern Alberta; and the mainland northern Canadian territories to the east of a line extended north from the Saskatchewan/Alberta border (Northwest Territories and Nunavut). In total it covers approximately 8 million square kilometers. It covers even more area and stretches till the Western Cordillera in the west and Appalachians in the east but the formations are still underground.
The underlying rock structure does include Hudson Bay and the submerged area between North America and Greenland.
Geology
Such a large area of exposed, old rock requires some explanation. The current surface expression of the Shield is one of very thin soil lying on top of the bedrock, with many bare outcrops. This arrangement was caused by severe glaciation during the last ice age, which covered the Shield and scraped the rock clean. The multitude of rivers and lakes in the entire region is caused by the watersheds of the area being so young and in a state of sorting themselves out with the added effect of post-glacial rebound. The Shield was originally an area of very large mountains and much volcanic activity, but over the millennia the area was eroded to its current topographic appearance of relatively low relief.
Mountains have deep roots and float on the denser mantle much like an iceberg at sea. As mountains erode, their roots rise and are eroded in turn. The rocks that now form the surface of the Shield were once far below the earth's surface. The high pressures and temperatures at those depths provided ideal conditions for mineralization.
The North American craton is the bedrock forming the heart of the North American continent and the Canadian Shield is the largest exposed part of the craton's bedrock.
Mining and Economics
The Shield is one of the world's richest areas in terms of mineral ores. It is filled with substantial deposits of nickel, gold, silver, and copper. Throughout the Shield there are many mining towns extracting these minerals. The largest, and best known, is Greater Sudbury, Ontario. Sudbury is an exception to the normal process of forming minerals in the Shield since there is significant evidence that the Sudbury Basin is an ancient meteorite impact crater.
The Shield, particularly the portion in the Northwest Territories, has recently been the site of several major diamond discoveries. The kimberlite pipes in which the diamonds are found are of relatively recent origin, and one theory of their origin suggests that the Shield was at some time in the past above a hotspot in Earth's mantle (much like the one that formed Hawaii, but under land rather than ocean). The spot lifted the surrounding landscape as the continent drifted over it, forming the pipes in various locations. The line of subsurface mountains that runs from the eastern seaboard of the United States nearly to Europe before culminating in the Challenger Seamount would, if run backwards in time, follow a path that matches what is suggested.
The Shield is also covered by vast boreal forests that support an important logging industry.
[edit] The Interior Plains
The Interior Plains of Canada are part of the vast North American Magnificent Plains region that stretch from the Arctic Ocean to the Gulf of Mexico. In Canada, the Interior Plains extend from the 49th parallel north to the Arctic Ocean, a distance of 2700 km. They are about 1300 km wide in the south, but only 275 km wide in the north. The southwestern section of the Interior Plains is part of the Great Plains proper.
The interior plains were often covered by shallow inland seas. Sediments from the Shield and the Rocky Mountains were deposited in these seas over millions of years. Eventually, the sediments were compressed by the weight of the layers above into sedimentary rock. Part of the sedimentary rock deposited in these areas consists of coral reefs that formed during the Paleozoic Era. Glaciers have had a visible effect on the landscape of the region. Glacier deposits created the gentle, rolling landscapes and their waters created major lakes, such as Lake Winnipeg, Lake Manitoba, Lake Winnipegosis, and Cedar Lake. The soil that has developed in this region is extremely fertile, giving the region the nickname of "Canada's Breadbasket."
[edit] The Great Lakes-St. Lawrence Lowland Landform Region
The Great Lakes And St. Lawrence lowlands, the industrial heartland of Canada, contain Canada's two largest cities, Montreal and Toronto. Fifty percent of Canadians live and 70 percent of Canada's manufactured goods are produced in this region. The region also has prime agricultural land, for example the Florida peninsula. The large expanses of Lake Erie and Lake Ontario extend the number of frost-free days, permitting the cultivation of grapes, peaches, pears and other fruits. The Great Lakes and St. Lawrence Region is sugar maple country. In the autumn, the maple tree's leaves, Canada's national symbol, are ablaze in red, orange and gold. The sap is collected in spring and evaporated to make maple syrup and sugar, a culinary delicacy first prepared and used by the Aboriginal North American Peoples.
| Geography of the Provinces and territories of Canada | ||
|---|---|---|
| National | Geography of Canada • Canada's landforms |
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| Provinces | British Columbia • Alberta • Saskatchewan • Manitoba • Ontario • Quebec • New Brunswick • Nova Scotia • Prince Edward Island • Newfoundland and Labrador | |
| Territories | Yukon • Northwest Territories • Nunavut | |
| See also | Regions of Canada • Islands • Rivers • Lakes • Mountains • Canadian National Parks | |
