The Canadian Shield is a plateau that covers approximately half of Canada, as well as most of Greenland and a portion of the northern United States. It is the oldest part of the North American plate and the largest formation of exposed Precambrian rock in the world.
Other names for the Canadian Shield include the Precambrian Shield and the Laurentian Plateau. It is made of primarily of granite and covers 1.7 million square miles. In addition to granite, it contains deposits of iron, gold, silver, uranium, platinum, nickel and copper. Diamonds are also found in the Canadian Shield and are mined in Canada's Northwest Territories. Some of the world's oldest-known fossils lie in the Canadian Shield; fossil bacteria and algae in the region date back about 2.2 billion years.
Four mountain ranges rise from the Canadian Shield: the Adirondack Mountains and Superior Highlands in the United States and the Laurentian and Torngat Mountains in Canada. The current topography of the Canadian Shield dates back to the movement of glaciers during the most recent ice age, and it varies from 1,000 to 5,000 feet above sea level. The highest points of the Canadian Shield are on Baffin Island and in northern Labrador.