Built by a geologist

The Canadian Shield

The Canadian Shield The Canadian Shield also called the Precambrian Shield or Laurentian Plateau is one of the most remarkable geological features on Earth. Covering roughly half of Canada's landmass — about 8 million km² — it is the exposed portion of the ancient North American craton. What Is a Craton? A craton is a stable, ancient block of continental crust that forms the core of a continent. Cratons have survived billions of years of plate tectonics, mountain building, and erosion. The Canadian Shield is the exposed surface of the North American Craton , sometimes called Laurentia . Age and Formation The Canadian Shield contains some of the oldest rocks on Earth : - The Acasta Gneiss in the Northwest Territories is dated at 4.03 billion years — the oldest known intact crustal rock on Earth - The Nuvvuagittuq greenstone belt in northern Quebec contains rocks that may be as old as 4.28 billion years - Most of the Shield formed between 4.0 and 1.0 billion years ago through repeated cycles of volcanic activity, sedimentation, metamorphism, and mountain building Why Is It Exposed? The Shield is "exposed" because billions of years of erosion have stripped away younger overlying rocks and sediments. The repeated advance and retreat of glaciers during the Pleistocene the last 2.6 million years further scoured the surface, removing soil and exposing the hard, ancient bedrock beneath. Geography The Shield extends across: - Most of Ontario and Quebec north of the Great Lakes and St. Lawrence - All of Nunavut and most of the Northwest Territories - Northern Manitoba and Saskatchewan - Much of Labrador - Parts of the northern United States Minnesota, Wisconsin, Michigan, New York Its landscape is characterised by thin, rocky soil , thousands of lakes carved by glaciers , boreal forest, and vast expanses of exposed bedrock. Geological Provinces of the Shield The Canadian Shield is divided into several geological provinces , each representing a distinct episode of crustal formation: | Province | Age Ga | Notable Features | |----------|----------|-----------------| | Slave Province | 4.03–2.5 | Acasta Gneiss, Ekati diamonds | | Superior Province | 3.0–2.5 | World's largest Archean craton, Sudbury impact | | Churchill Province | 2.0–1.7 | Trans-Hudson Orogen | | Grenville Province | 1.3–1.0 | Roots of ancient mountains | Economic Importance The Canadian Shield is one of