Animated Map of North America 18,000 Years Ago
Courtesy of the Illinois State Museum
KYA: Thousands of Years Ago
Calgary & Southern Alberta
Glaciers covered most of what is now Canada 18,000 years ago. Parts of present-day Alaska, Yukon, and Alberta, however, were free of ice. Because the glaciers locked up so much water, ocean levels were lower. Where the oceans had been shallow, new land had appeared. A huge "land bridge" called Beringia linked Asia and North America. As the climate warmed and became drier, the ice sheets retreated.
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Prehistoric Environments
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Grasslands expanded northward, reaching their greatest extent between 7,500 and 3,500 years ago, when Alberta's climate was considerably warmer than it is today. As the climate cooled to present standards, the landscape of what is now southern Alberta began to assume its modern appearance. Southern Alberta today has a Cold Continental climate. Temperatures in Calgary range from highs of 30° C or more in summer, to lows of -40° C in winter. Although the prevailing winds are from the northwest, warm westerly winds frequently blow through the mountain passes. These "Chinooks" periodically alleviate the normally cold winter temperatures, and prevent excessive snow cover. Lying in the lee of the Rocky Mountains, the region as a whole has a dry climate. The average precipitation in Calgary, for example, is a modest 43 centimetres a year, with about fifteen centimetres usually falling as snow. The region becomes progressively drier as one moves southeastward. Because of this variation, southern Alberta supports a number of different vegetation communities. Encircling the dry short-grass prairie zone of southeastern Alberta is a mixed-grass area composed of indigenous plants such as needlegrass, rough fescue and northern wheatgrass. Included in this mixed-grass belt is a zone of aspen parkland, an ecotone grading into grassland to the south, mixed wood forest to the north, and the mountain forests to the west. |
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