Lecture9

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• The internal composition of Earth is inferred by relating calculated seismic wave velocities to properties of rocks and minerals at temperatures and pressures equivalent to Earth's interior.
• The crust-mantle boundary (Moho) displays a sharp discontinuity in seismic velocity where mafic to felsic igneous and metamorphic crustal rocks are underlain by mantle peridotite.
• The low-velocity zone (~100 km depth) is evidence that part of the upper mantle is less rigid and may be partly molten. This is the top of the asthenosphere, below the rigid lithosphere (crust and upper mantle).

8.4 What composes the interior of Earth?