Monday, March 10, 2008

Journey To the Inner Inner Core of the Earth

The inner inner core of the Earth: Texturing of iron crystals from three-dimensional seismic anisotropy. 2008. X. Sun and X. Song. Earth and Planetary Science Letters. Available online 19 February, 2008.

Cave Carson © DC Comics
From the press release:

Scientists have confirmed the discovery of Earth’s inner, innermost core, and have created a three-dimensional model that describes the seismic anisotropy and texturing of iron crystals within the inner core.

Using both newly acquired data and legacy data collected around the world, Song and postdoctoral research associate Xinlei Sun painstakingly probed the shape of Earth’s core.

Composed mainly of iron, Earth’s core consists of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. The inner core plays an important role in the geodynamo that generates Earth’s magnetic field.

The solid inner core is elastically anisotropic; that is, seismic waves have different speeds along different directions. The anisotropy has been found to change with hemisphere and with radius. What they found was a distinct change in the inner core anisotropy, clearly marking the presence of an inner inner core with a diameter of about 1,180 kilometers, slightly less than half the diameter of the inner core.

The layering of the core is interpreted as different texturing, or crystalline phase, of iron in the inner core, the researchers say.