Canadian Shield

Canadian Shield or Laurentian Plateau (lôrĕn`chən), U-shaped region of ancient rock, the nucleus of North America, stretching N from the Great Lakes to the Arctic Ocean. Covering more than half of Canada, it also includes most of Greenland and extends into the United States as the Adirondack Mts. and the Superior Highlands. The first part of North America to be permanently elevated above sea level, it has remained almost wholly untouched by successive encroachments of the sea upon the continent. It is the earth's greatest area of exposed Archaean-age rock; the metamorphic rocks of which it is largely composed were probably formed in the Precambrian era. Repeatedly uplifted and eroded, it is today an area of low relief (c.1,000–2,000 ft/305–610 m above sea level) with a few monadnocks and low mountain ranges (including the Torngat and Laurentian Mts.) probably eroded from the plateau during the Cenozoic era. During the Pleistocene epoch, continental ice sheets depressed the land surface (see Hudson Bay), scooped out thousands of lake basins, and carried away much of the region's soil. Drainage is generally very poor on the shield. The southern part of the shield has thick forests while the north is covered with tundra. The region is largely undeveloped but has great water-power potential and is a source of minerals, timber, and fur-bearing animals.

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Canadian Shield

One of the world's largest geologic continental shields, centred on Hudson Bay and extending for 3 million sq mi (8 million sq km) over Canada from the Great Lakes to the Canadian Arctic and into Greenland, with small extensions into northern Minnesota, Wisconsin, Michigan, and New York. It is the largest mass of exposed Precambrian rock on earth. The region as a whole is composed of ancient crystalline rocks whose complex structure attests to a long history of uplift and depression, mountain building, and erosion.