title: Accretion of the Earth and segregation of its core.
abstract: The Earth took 30-40 million years to accrete from smaller 'planetesimals'. Many of these planetesimals had metallic iron cores and during growth of the Earth this metal re-equilibrated with the Earth's silicate mantle, extracting siderophile ('iron-loving') elements into the Earth's iron-rich core. The current composition of the mantle indicates that much of the re-equilibration took place in a deep (> 400 km) molten silicate layer, or 'magma ocean', and that conditions became more oxidizing with time as the Earth grew. The high-pressure nature of the core-forming process led to the Earth's core being richer in low-atomic-number elements, notably silicon and possibly oxygen, than the cores of the smaller planetesimal building blocks.
authors.affiliation: Macquarie University, Department of Earth and Planetary Sciences, North Ryde, New South Wales 2109, Australia. bwood@els.mq.edu.au
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Wood
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Walter
authors.forename: Jonathan
authors.initials: J
authors.lastname: Wade