|Canada is a huge country (9,972,800 km2). It extends about 4,800 km from the Atlantic shore of
Newfoundland and Labrador to the Pacific Ocean and Alaskan border and about 4,500 km from its southern boundary to the limit of land in northern Ellesmere Island. One-third of the country can be defined broadly as Arctic, and the northernmost areas are made up of the
islands of the Canadian Arctic Archipelago, totalling some 1,295,000 km2. The northeastern part of the mainland is divided by Hudson Bay, a 1,000 km-wide arm of the cold northern seas. |
Canada's physiography is dominated by the Cordillera, a great mountainous area in the west that reaches southward to Central America. The Canadian Cordillera comprises three distinct elements: the western Coast Range, the eastern Rocky Mountains, and a complex interior system. Valley areas occur between the ranges. East of the mountains, relief falls rapidly to the flatter centre of the continent. There are also areas of marked relief in the east and in the northeastern Arctic.
The core of the eastern half of Canada is the Canadian Shield, a massive and rather complex area of resistant Precambrian crystalline rock. Glaciation has produced an abundance of aquatic habitats on this impenetrable substrate. Such aquatic habitats, together with huge lakes held mainly in faults widened by glaciation, provide Canada with 20 per cent of the world's fresh water. Not only does Canada include part of four of the Great Lakes (Superior, Huron, Ontario and Erie), but it also has giant lakes farther west and north including Lakes Nipigon, Manitoba, Winnipeg, Winnipegosis, Reindeer, Athabasca, Great Slave, and Great Bear. Some coastal areas are drained by local rivers, but the country also has several enormous rivers, such as the St. Lawrence in the east and the Nelson, Yukon, Fraser, and Mackenzie in the west.
|The western mountains influence Canada's climate and the organisms that live there. Air flows
originating over the Pacific Ocean bring wet air to the west coast, and rain or snow to the coastal mountain slopes.
The mountain valleys of the western interior, however, receive very little rain. Rainfall increases toward
the east, where northern and southern air masses mix with the eastward flow. Climates are
less arid toward the north, except in Arctic polar deserts. |
The uniformity of relief and climate over large areas, the severity of conditions in the north, and past glaciation (which eliminated the biota in most places) reduce the complexity of the Canadian environment. However, the extent of the land surface (and variety of physiographic, climatic and soil factors), the numerous bodies of freshwater, and the topographic variety of the mountains enhance organic diversity and give it recognizable regional components.