The Mantle

The Earth's mantle is composed of crystalline structures that transform into denser arrangements as pressure and temperature rise during descent. As John Baez tells it, these changes create distinct boundaries, such as the four hundred ten kilometer discontinuity where olivine transforms into wadsleyite, a mineral capable of holding vast amounts of water. Further down, at six hundred sixty kilometers, the rock decomposes into bridgmanite, which is likely the most abundant mineral on the planet. This complex layering influences how massive slabs of cold rock sink toward the core-mantle boundary.

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