The Canadian Shield is Canada's largest physiographic region extending from Alberta eastward to Newfoundland & Labrador and northward to Greenland, the Northwest Territories and Nunavut. The Shield covers a total area of 4.8 million square kilometres, and almost two thirds of Ontario.
The Canadian Shield is composed of Precambrian rocks that are more than 570 million years old. Some of these rocks are even over 2 billion years old, making the rocks of the Canadian Shield the oldest rocks in North America. The rocks are igneous (including granites, diorites and basalts) and metamorphic (including schists and marbles). The Shield was the first area elevated above sea-level in North America and has undergone many changes over its geologic history, rising, falling and being eroded and scoured by the elements to become some of the most stable rocks present on Earth.
The Shield has helped shape Canada's cultural history — the navigable waterways carved into the area during glaciations dictated settlement across its expanse by both Native and European settlers. The Hudson Bay, an extremely important body of water in Canada's early history, was created by depression in the Canadian Shield from continental ice sheets. The Shield is also a source for many important minerals including iron, nickel, copper, zinc, uranium, gold and silver, and has influenced the economy in Canada.