Accretion and primary differentiation of the Earth: A personal journey

The accretion of the Earth was a violent series of events dominated by the addition of objects one third to one tenth of the mass of the growing plane t. During the later stages of accretion, these collisions deposited enough energy to at least partly melt the Earth, possibly multiple times. The resu lt was an ocean of magma. Metal sank through this magma ocean and ponded at its base at roughly the depth of the base of the current upper mantle for some period of time before transiting diapirically through the lower mantle to the center of the planet. Metal appears to have equilibrated with silic ate at the base of the magma ocean. The primitive atmosphere and ocean appe ar to have outgassed from the magma ocean. Core formation, magma ocean soli dification, ocean and atmospheric outgassing were essentially complete by 4 .45 Ga ago. Copyright (C) 2000 Elsevier Science Ltd.