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  2. Shield (geology) - Wikipedia

    en.wikipedia.org/wiki/Shield_(Geology)

    A shield is that part of the continental crust in which these usually Precambrian basement rocks crop out extensively at the surface. Shields can be very complex: they consist of vast areas of granitic or granodioritic gneisses , usually of tonalitic composition, and they also contain belts of sedimentary rocks, often surrounded by low-grade ...

  3. Craton - Wikipedia

    en.wikipedia.org/wiki/Craton

    The term craton is used to distinguish the stable portion of the continental crust from regions that are more geologically active and unstable. [4] Cratons are composed of two layers: a continental shield, in which the basement rock crops out at the surface, [5] and a platform which overlays the shield in some areas with sedimentary rock. [6]

  4. Continental crust - Wikipedia

    en.wikipedia.org/wiki/Continental_crust

    The thickness of Earth's crust (km). The continental crust consists of various layers, with a bulk composition that is intermediate (SiO 2 wt% = 60.6). [5] The average density of the continental crust is about, 2.83 g/cm 3 (0.102 lb/cu in), [6] less dense than the ultramafic material that makes up the mantle, which has a density of around 3.3 g/cm 3 (0.12 lb/cu in).

  5. List of shields and cratons - Wikipedia

    en.wikipedia.org/wiki/List_of_shields_and_cratons

    A craton is an ancient part of the Earth's continental crust which has been more or less stable since Precambrian times. Cratons whose ancient rocks are widely exposed at the surface, often with relatively subdued relief, are known as shields.

  6. Canadian Shield - Wikipedia

    en.wikipedia.org/wiki/Canadian_Shield

    The Canadian Shield (French: Bouclier canadien [buklje kanadjɛ̃]), also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the ancient geologic core of the North American continent.

  7. Oldest dated rocks - Wikipedia

    en.wikipedia.org/wiki/Oldest_dated_rocks

    The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history, and mark the start of the Archean Eon, which is defined to start with the formation of the oldest intact rocks on Earth.

  8. Laurentia - Wikipedia

    en.wikipedia.org/wiki/Laurentia

    Laurentia basement rocks. Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America.Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and the Hebridean terrane in northwest Scotland.

  9. Earth's crust - Wikipedia

    en.wikipedia.org/wiki/Earth's_crust

    The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4.28 billion years [18] [19] and have been found in the Narryer Gneiss terrane in Western Australia, in the Acasta Gneiss in the Northwest Territories on the Canadian Shield, and on other cratonic regions such as those on the Fennoscandian Shield.