MANITOBA, the most easterly of the three Prairie Provinces of Canada, bounded by long. 102° W. (approx.) on the west, by lat. 6o° N. on the north, by lat. 49° N. on the south and by long. 95° W. on the south-east. To the north-east it extends to the shores of Hudson's bay.
Manitoba has the oldest farming settlements in western Canada, and after taking up land in the S.W. of Manitoba about the junc tion of the Red River and the Assiniboine, settlers went on to develop south Saskatchewan and Alberta, leaving northern and eastern Manitoba little occupied even to-day. The reasons are purely geographical. Topographically the province may be divided into three main areas (see map). The Laurentian Shield area; the Red River lowland ; the Western Plateaus ; all three crossed by an even more important line, viz., that dividing the heavy forest on the north from the light Grove and true prairie areas in the south.
The Laurentian Shield area is developed on Pre-Cambrian usually crystalline—rocks. It is an area of low hummock relief, much bare scraped rocks and innumerable lakes. It is wholly forested and presents few promising agricultural areas. The Red River lowland lies only a little lower than the Laurentian country, the Pre-Cambrian rocks of which dip imperceptibly beneath the undisturbed Palaeozoic limestones which floor this region. The lowland is occupied by Lakes Winnipeg, Winnipegeosis and Mani toba, and by the Red River itself. Much of it is very flat, and the general level is about 800'. From the latitude of the south end of L. Winnipeg northwards the land is forested with only oc casional areas of cleared farm land. South of the lake to the International Boundary this lowland had never more than scat tered groups of trees and much was true prairie. This portion is all now cleared and coveted with highly developed farms.
The Western Plateaus, from south to north, viz., Pembina, Rid ing, Duck and Porcupine Mountains, present an almost continuous Cretaceous scarp overlooking the Palaeozoic lowland to the East. All but Pembina were heavily forested and now remain as forest reserves. Together they form a plateau-like mass which sinks quite gently a little toward the Saskatchewan border, and is breached by the Pembina, Assiniboine and Swan Rivers, on their way eastward to the Red River lowland. The south-western por
tion of this second prairie steppe, as it is sometimes called, about the Assiniboine and Souris river, is real prairie and largely settled. Rising steeply above this second steppe is the scrub covered Ter tiary residual plateau of Turtle Mountain.
The whole of the province has been glaciated, and with the final retreat of the ice to the north of the water parting between the Minnesota and the Red River, a glacial lake was formed (Lake Agassiz) enclosed by this water-parting to the south, by land rising gradually to the east, and sharply to the west, and by the ice to the north. Stratified lacustrine deposits cover the glacial till over much of the lowland.
The soils of the prairie and grove portion of southern Manitoba are very dark brown or black loams and clays of extraordinary fertility. As elsewhere in the prairie proper, the climatic condi tions have "favoured intensive and rapid growth for a period of the year coinciding with the greatest rainfall, followed by dry cold weather, which delays and often almost entirely prevents the decomposition and loss of organic matter and plant foods until the following spring, when temperature and moisture again per mit the rapid preparation of foods for plants at a time when they are in greatest demand. The above conditions have been re sponsible for the present vegetation covering these plains, and this native vegetation has been responsible for the nitrogen and organic matter content of the soils." Poorer soils form put of the delta (formed in old Lake Agassiz) of the Assiniboine and there is a small forest reserve just south of that river. These are comparatively small areas.