<Tr> <Td_colspan="2"> The Canadian Shield is a broad region of Precambrian rock (pictured in shades of red) that encircles Hudson Bay . It spans eastern, northeastern, and east - central Canada and the upper midwestern United States . </Td> </Tr> <P> The Canadian Shield, also called the Laurentian Plateau, or Bouclier canadien (French), is a large area of exposed Precambrian igneous and high - grade metamorphic rocks (geological shield) that forms the ancient geological core of the North American continent (the North American Craton or Laurentia). Composed of igneous rock resulting from its long volcanic history, the area is covered by a thin layer of soil . With a deep, common, joined bedrock region in eastern and central Canada, it stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada; it also extends south into the northern reaches of the United States . Human population is sparse, and industrial development is minimal, while mining is prevalent . </P> <P> The Canadian Shield is a physiographic division, consisting of five smaller, physiographic provinces: the Laurentian Upland, Kazan Region, Davis, Hudson and James . The shield extends into the United States as the Adirondack Mountains (connected by the Frontenac Axis) and the Superior Upland . The Canadian Shield is U-shaped and is a subsection of the Laurentia craton signifying the area of greatest glacial impact (scraping down to bare rock) creating the thin soils . The Canadian Shield is more than 3.96 billion years old . The Canadian Shield once had jagged peaks, higher than any of today's mountains, but millions of years of erosion have changed these mountains to rolling hills . </P> <P> The Canadian Shield is a collage of Archean plates and accreted juvenile arc terranes and sedimentary basins of the Proterozoic Eon that were progressively amalgamated during the interval 2.45 to 1.24 Ga, with the most substantial growth period occurring during the Trans - Hudson orogeny, between ca . 1.90 to 1.80 Ga . The Canadian Shield was the first part of North America to be permanently elevated above sea level and has remained almost wholly untouched by successive encroachments of the sea upon the continent . It is the Earth's greatest area of exposed Archean rock . The metamorphic base rocks are mostly from the Precambrian Supereon (between 4.5 billion and 540 million years ago), and have been repeatedly uplifted and eroded . Today it consists largely of an area of low relief 300 to 610 m (980 to 2,000 ft) above sea level with a few monadnocks and low mountain ranges (including the Torngat and Laurentian Mountains) 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 . </P>

What are the major landforms in the canadian shield