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Contents of 8.4 What composes the interior of Earth?

• Crystal-structure transformations of peridotite minerals at high temperature and pressure explain the abrupt increase in seismic velocity at about 410 and 660 km depth. The interval between is the transition zone between upper mantle (shallower than 410 km) and lower mantle (deeper than 660 km).
• The core is likely composed of iron or nickel-iron. The outer core is molten, and the inner core solid. The outer core must have ~10% lighter elements (O, S, Si, K, H) to match the calculated seismic velocities.

8.4 What composes the interior of Earth?