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Feb22-07, 02:52 PM
P: 748
Well I think it would probably be agreed that some of the core came from early impacts, if you're suggesting that we were hit by a large ball of iron that eventually found its way down to the centre of the earth then no, that didn't happen.

A large impact would have melted (some of) the earth by the mechanism of decompressional melting, caused by a phase of decompression immediately following the impact. It is actually thought that this would cause a plume in the upper mantle, perhaps somehow this helped get plate tectonics going?