If scientists can gain a better understanding of the core-mantle boundary’s behavior, it will give them clues as to how Earth’s internal convection works there, where cool tectonic plates descend from the ocean floor through the mantle eventually nearing the dense, liquid-iron outer core, heat up, and begin moving upward again in a repeated cycle that mixes material and heat through the mantle.
Below the Earth’s crust stretches an approximately 1,800-mile-thick mantle composed mostly of a mineral called magnesium silicate perovskite (MgSiO3). Below this depth, the pressures are so high that perovskite is compressed into a phase known as post-perovskite, which comprises a layer 125 miles thick at the core-mantle boundary. Below that lies the Earth’s iron-nickel core.
The current experiment showed that post-perovskite’s crystal structure is deformed by pressure into a more elongated shape. Because seismic waves travel faster in the stretched direction, this matches the observed difference in velocity between seismic waves polarized horizontally and vertically traveling through the post-perovskite zone above the Earth’s core.
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