Mantle transition zone

The mantle region roughly 410–660 kilometers below Earth’s surface, where increasing pressure transforms olivine into denser minerals and changes seismic-wave speeds.

Olivine: A magnesium-iron silicate mineral that dominates much of the upper mantle. Its high-pressure transformations define the zone’s principal discontinuities.
Earth's mantle: The thick silicate-rock layer between Earth’s crust and metallic core. The transition zone is a depth-defined region within this layer.
Water in the mantle: Hydrogen-bearing material stored in mantle minerals and melts. Wadsleyite and ringwoodite can incorporate water, making the zone a potential reservoir.
Mantle discontinuity at 410 km: A seismic boundary near 410 kilometers depth associated mainly with olivine transforming into wadsleyite. Its depth varies with temperature and helps map conditions in the zone.
Wadsleyite: A dense high-pressure form of magnesium-iron silicate stable in the upper mantle. It forms from olivine near the 410-kilometer boundary.
Seismic wave: An elastic disturbance that travels through Earth and carries information about its interior. Seismic waves reveal changes in mineral properties across the zone.
Mantle convection: The slow circulation of solid mantle rock driven by internal heat. Mineral density changes across the zone can influence circulation between upper and lower mantle.
Mantle discontinuity at 660 km: A seismic boundary near 660 kilometers depth marking the transition toward lower-mantle mineral assemblages. Its sharpness and topography bear on how readily mantle material crosses the zone.
Ringwoodite: A dense, high-pressure magnesium-iron silicate with a spinel crystal structure. It becomes stable deeper in the zone and can host substantial water.
Seismology: The study of earthquakes and the waves they generate. Seismic imaging provides most evidence for the zone’s boundaries and structure.

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