Precambrian shield: largest geological and physiographic region of canada; flat landscape of forest, bogs, water bodies and rock outcrops; landscape much affected by the influence of a number of continental glaciations (last ended about. Hudson platform: sedimentary in origin (read below) Interior platform: northern part of a much more extensive regions called the. Great plains in the u. s; accounts for many political, social and economic patterns because of its orientation (north-south along with the cordilleran. Great lakes-st. lawrence platform: also extends into the u. s (sedimentary in origin) In southern parts of the precambrian shield, the boreal forest has been commercially exploited for almost 200 years, but becoming sparser and commercially unproductive (moving north towards the treeless tundra). This is the perfect habitat for beavers, enabling the early fur trade (2nd staple in the economy of canada). This created rapid settlement and development of southern ontario and.