Borderlands: Cordilleran Physiographic Region

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Abstract

Canada’s landscape is very diversified and comprises several distinctive areas, called physiographic regions, each of which has its own topography and geology. This map shows the location of the Cordilleran physiographic region.

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The physical geography of Canada comprises two great parts: the Shield and the Borderlands. The Shield consists of a core of old, massive, Precambrian crystalline rocks. The Borderlands areas are formed by younger rocks and surround the Shield like two rings. The inner ring comprises a chain of lowlands, plains and plateaus of generally flat-lying sedimentary rocks. The outer ring consists of discontinuous areas of mountains and plateaus in which the younger rocks are deformed. Each of these areas is divided into regions, each of which comprises many smaller subdivisions that are distinctive based on their topography and geology.

Cordilleran Physiographic Region

The Cordilleran Region is divided into three large linear zones called the Eastern System, the Interior System and the Western System. Each system is further divided into areas and subdivided into mountains, ranges, plateaus, hills, valleys, trenches, basins and plains. Each has its own geological and physiographic characteristics. The Cordillera is also divided transversely into a number of segments by east-west belts of relatively low terrain.

In the Interior and Western systems, some landforms have been produced by volcanic processes. Most striking, however, are three great shield-like volcanoes in the northwestern part of the Interior Plateau and a group of similar volcanoes on the Stikine Plateau. Also on the Stikine Plateau are a number of flat-topped volcanoes that erupted during the Pleistocene Epoch (the Ice Age between about 80 000 and 10 000 years before the present time). A large number of small volcanoes and cinder cones occur singly, in line or in groups. These range in age from pre-Pleistocene to within a few hundred years of the present and vary in height up to a few tens of metres. For more information, refer to the map on Major Volcanic Areas in Environment / Natural Hazards.

The following photographs are examples of landscape from the Cordilleran Region.

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Upper Kananaskis River, Alberta

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Pelly Mountains, Yukon