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Wednesday, November 27, 2013

Life Created the Continents ...


On live-Earth, algae, bacteria and more complex life colonise the new land, erode it and dump masses of sediment into the ocean. The sediment – 40 per cent water by weight – is eventually pulled down more than 100 kilometres beneath the surface by early subducting tectonic plates, where piping hot temperatures release the trapped water. The hydrated mantle is viscous and more buoyant, so it rises and bursts through the surface in volcanic eruptions that add to the continental plate. "This is the major factor for how life enhances the continental formation rate," says Höning. 
In the model, live-Earth settles into an equilibrium where plate tectonics create as much continental crust as it destroys. About 40 per cent of the surface is covered in continent, much like today. 
The big surprise came from dead-Earth. There, the mantle is drier, so continental crust is produced much more slowly. The planet becomes a stable water-world, with very little continental land.

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