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Accretion of the Earth and segregation of its core
Ist Teil von
Nature, 2006-06, Vol.441 (7095), p.825-833
Ort / Verlag
London: Nature Publishing
Erscheinungsjahr
2006
Quelle
Psychology & Behavioral Sciences Collection
Beschreibungen/Notizen
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.