REWIND Earth's story 3 or 4 billion years, to when life was emerging. The surface of our planet was starting to cool but still piping hot – possibly about 200 °C. Early, unstable continents may have been forming. Now imagine life doesn't emerge, and press play.
The pair included biological weathering in one modelled Earth, and left it out of another. Press play on both Earths at 4 billion years ago, and for the first 1.5 billion years, there is very little difference between them. By about 2.5 billion years ago, early continental plates emerge above the ocean, regardless of life. But then, everything diverges.
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.
http://www.newscientist.com/article/mg22029443.100-early-life-built-earths-continents.html#.Usx6M9JdWSp
(Thanks to Flash for sending the link.)
(Thanks to Flash for sending the link.)
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