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
When the
The underlying rock structure does include Hudson Bay and the submerged area between North America and Greenland.
The Canadian shield is so large the climate varies across it. In the southern parts the climate is seasonal; the average temperature in the winter is -18 degrees Celsius, and in the summer it is 25 degrees Celsius. The growing season of about 120 days coincides with summer daylight averaging about 15 hours, while winter daylight averages about 8.5 hours. In the northern parts it is very cold. The average temperatures range from 15 degrees Celsius in the summer to -35 degrees Celsius in winter. The growing season is only 60 days. Winter daylight hours are about 5.5 hours, and in the summer the daylight hours are about 18.5 hours. The lowlands of the Canadian shield have soggy soil suitable for planting trees, but it contains many marshes and bogs. The rest of the region has coarse soil that doesn't hold moisture very well and is frozen all year round. Forests are less dense in the north.
Such a large area of exposed old rock is unusual. The current
Mountains have deep roots and float on the denser mantle much like an iceberg at sea. As mountains erode, their roots rise and are eroded in turn. The rocks that now form the surface of the Shield were once far below the earth's surface. The high pressures and temperatures at those depths provided ideal conditions for mineralization.
The
The Canadian Shield is part of an ancient continent called Arctica, which was formed about 2.5 billion years ago, during the Neoarchean era. It was split into Greenland, Laurasia, Scotland, Siberia, East Antarctica and is now roughly situated in the Arctic around the current North Pole.
The Shield is one of the world's richest areas in terms of
The Shield, particularly the portion in the Northwest Territories, has recently been the site of several major diamond discoveries. The kimberlite pipes in which the diamonds are found are closely associated with cratons, which provide the deep lithospheric mantle required to stabilize diamond as a mineral. The kimberlite eruptions then bring the diamonds from over 150 km depth to the surface. Currently the Ekati and Diavik mines are actively mining kimberlite diamonds.
The Shield is also covered by vast