Continental crust

The continental crust is the layer of granitic and sedimentary rock which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. It is less dense and more rigid than the material of the Earth's mantle and thus "floats" on top of it. Continental crust is also less dense than oceanic crust, though it is considerably thicker, averaging 20 to 80 km versus the average oceanic thickness of around 5-10 km. As a consequence, when active margins of continental crust meet oceanic crust in subduction zones, the oceanic crust is subducted. Its relative low density keeps the continental crust from being subducted or re-cycled back into the mantle. For this reason the oldest rocks on Earth are within the "cratons" or cores of the continents, rather than in repeatedly recycled oceanic crust.

Related Topics:
Granitic - Sedimentary - Continent - Continental shelves - Dense - Mantle - Oceanic crust - Subduction zone - Subducted - Craton

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Continental crust is thickest beneath mountain ranges with a deep root. This fact results from the isostatic uplift associated with orogeny (mountain formation). As it is still being formed today, the amount of continental crust has been increasing over geological time. About 40% of the Earth's surface is now underlain by continental crust.

Related Topics:
Isostatic uplift - Orogeny

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