Physical Geography

Manitoba lies within three major physiographic regions of North America: the Canadian Shield, the Interior Plains, and the Hudson Bay Lowland.

Much of the province, except in the northeast and the south and southwest, lies in the Canadian Shield. It is mainly an area of ancient crystalline rock whose surface features were formed by glaciers. The advancing and retreating ice eroded the rock, deposited debris, and created a vast number of lakes. Muskegs (bogs) are widespread. Large tracts are covered with dense coniferous forests. Throughout the area, population is sparse.

The south-central and southwestern parts of Manitoba lie within the Interior Plains. This is the settled part of the province; it is a fertile agricultural region, much like the northern prairie and plains states of the United States. Although occasionally rolling, the terrain is predominantly flat.

Most of the region was part of the lake bed of glacial Lake Agassiz, which during the Ice Age covered an area larger than that of the present Great Lakes. The only land that rose above the lake was in a section of relatively high prairies and hills west of a sharp escarpment running southeastward from the Saskatchewan River. There, amid rolling prairies, rises Baldy Mountain, Manitoba's highest point (2,729 feet [832 m]). Only slightly lower are the Porcupine Hills and Riding Mountain, site of Riding Mountain National Park.

The Hudson Bay Lowland is largely a semi-barren, uninhabited, and poorly drained tundra region fringing Hudson Bay in the northeast. Most of it is only slightly above sea level. Most of the surface in the north is underlain by permanently frozen ground called permafrost.

Water. Manitoba's principal lakes—Winnipeg, Winnipegosis, and Manitoba—are remnants of old Lake Agassiz. Lake Winnipeg is larger than Lake Ontario and is almost as large as Lake Erie. Of similar origin are nearby Cedar and Moose lakes. Thousands of other lakes, large and small, dot the Canadian Shield. Most are irregular in shape, and many interconnect to form chains. Parts of Reindeer Lake and Lake of the Woods are also within the province.

Two large rivers, the Churchill and the Nelson, drain most of Manitoba. Both flow northeastward to Hudson Bay. The Nelson is the more important system, for it flows from Lake Winnipeg, which receives such major rivers as the Assiniboine, Red, and Winnipeg. Other large rivers include the Seal in the north and the Hayes in the east. Hydroelectric stations on Manitoba's rivers provide more than 90 per cent of the province's electrical power.

Climate. Because of its northerly latitude and central location in North America, Manitoba has a cold climate that varies from continental in the south to subpolar in the center and north. Winters are bitterly cold and increase in length and severity from south to north. Average January temperatures range from about 0° to -20° F. (-17.8° to -28.9° C). Temperatures of -40° F. (-40° C.) and lower have been recorded throughout the province.

Summers are short and vary from warm to hot. July temperatures of more than 100° F. (37.8° C.) occur, but they average between 55° F. (12.8° C.) in the north and 70° F. (21.1° C.) in the south. The growing season is normally two to four months.

Annual precipitation is meager throughout Manitoba, varying from about 20 inches (508 mm) in the southeast to less than 14 inches (356 mm) in the north. The bulk of it comes as rain during the summer. Snow covers the ground all winter. Some of it is brought by occasional severe blizzards.