Geology

Journey to the Center of the Earth

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Science  11 Apr 2008:
Vol. 320, Issue 5873, pp. 156
DOI: 10.1126/science.320.5873.156a

The formation of Earth's core was the major differentiation of the early planet, segregating iron and other metal-loving elements to the planet's center, setting the conditions for a magnetic field, and releasing potential energy as heat. How was the iron localized so efficiently and quickly, displacing what was probably an early, semisolid silicate-rich core?

It is generally thought that heating by impacts (some of which contained iron protocores) and enhanced radiogenic decay allowed blobs of iron metal to form and accumulate in a magma ocean in the outer Earth. Golabek et al. explore the iron's subsequent inward migration. Like others, they propose that enough iron accumulated to allow the dense blobs to move toward the center of Earth, displacing the silicate protocore. They also suggest, and show through numerical simulations scaled to the early Earth, that an extensive network of iron melt channels likely surrounded each sinking diapir. As these drained, they would form additional and larger daughter diapirs to scavenge iron from the upper mantle into the growing core. — BH

Earth Planet. Sci. Lett. 10.1016/j.epsl.2008.02.033 (2008).

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