Canadian Shield

The Canadian Shield, also called the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks.

It is the world's largest area of Precambrian rock. It forms the North American Craton (or Laurentia), the ancient geologic core of the North American continent.

Glaciation has left the area with only a thin layer of soil, through which exposures of igneous bedrock resulting from its long volcanic history are frequently visible. Because of this, it forms a barrier to human settlement. 

The Shield stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada and most of Greenland; it also extends south into the northern reaches of the United States.