The Eart4 - continents. Oceanic ridges generate new crust...

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The Earth's lithosphere Note the crust is thicker under the land than under the oceans. The crust-mantle division is a compositional change, the crust-asthenosphere division is a change in plasticity. The crust-mantle interface is called the Moho (after Mohorovicic), a transition from lower density silicates to higher density silicates 0.1 to 0.5km thick, 5-10km below the ocean floor or 20-90 km beneath the continents. The crust sits in isostatic equilibrium on the magma. We know that the crust is divided into "plates" which move with respect to each other, gradually changing the alignment of the
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Unformatted text preview: continents. Oceanic ridges generate new crust at the rate of 17 km 3 per year, whereas at the continental boundaries a similar amount of material is subducted and recycled. Plate tectonics This continual movement of the continents can be traced back in time: see for example Beatty and Chaikin or a Geology/Palaeontology text book for the development of the continents from Gondwanaland and Pangea 100s of millions of years ago....
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The Eart4 - continents. Oceanic ridges generate new crust...

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