The Taiga Shield is located in Canada's Subarctic region, sweeping through much of southern Nunavut, northern Quebec, and almost all of Labrador. It is part of the Canadian Shield, and is a transition zone between the Boreal and Arctic zones. It was formed approximately 40 billion years ago, in the Precambrian era, when volcanoes brought magma to the surface of the Earth. This cooled and formed new land of igneous rock, and further eruptions, folding, and faulting, changed this land and also created metamorphic rock. Sedimentary rock was carried there by glaciers, which changed the landscape in other ways, too. They left it rugged and created rocky hills and mountains. Gravel and boulders alike were carried along; today they are dispersed haphazardly. Glacial lakes are scattered all the way from the North Atlantic to Great Slave Lake. These wetlands provide diversity for vegetation and wildlife.