LandformsIn Canada, the foothills of the ROCKY MOUNTAINS occupy an area between the Rockies and the Alberta plains and associated lowlands of northeastern BC. Covering about 60 000 km2, this region extends from the Canada-US border northwestward, a distance of some 1100 km, to the Peace River region of BC, and averages about 50 km in width. Summit elevations in the foothills average approximately 1800 m; the plains area to the east and the mountains to the west average about 1200 m and 2500 m respectively.
Most of the foothills of the Rockies consist of folded and faulted Mesozoic and Cretaceous sedimentary rocks that were deformed by mountain-building forces (the Columbian and Laramide Orogenies) that occurred during Cretaceous (144-66.4 million years ago) and early Tertiary (66.4 to 36.6 million years ago) times. The foothills were extensively glaciated during the Quaternary (1.6 million years ago to about 10 000 years ago). In the last major ice advance, the Wisconsin, the mountain (Cordilleran) glaciers and the Continental Ice Sheet merged and covered some areas of the foothills while other areas, especially in the Porcupine Hills in southern Alberta, remained ice free.
See also GLACIATION.
Author IAN CAMPBELL