Earth's mantle

Earth's mantle is the rocky layer between the crust and core, extending to about 2,900 kilometers depth and comprising most of Earth's volume. Its solid rock deforms and flows slowly over geological time.

Mohorovičić discontinuity: The boundary between Earth's crust and mantle, marked by a change in seismic-wave speeds. This seismic boundary marks the mantle's upper edge beneath both continents and oceans.
Mantle convection: The slow circulation of mantle material driven by internal heat and buoyancy. Convection transports heat through the mantle and contributes to plate motion.
Plate tectonics: The theory that Earth's lithosphere is divided into moving plates that interact at their boundaries. Mantle flow and sinking lithosphere help drive and accommodate plate motion.
Accretion of Earth: The gradual assembly of Earth from smaller solid bodies in the early Solar System. Earth's accretion supplied the material from which the mantle formed.
Whole-mantle convection: A model in which material circulates between the upper and lower mantle rather than remaining separated. The extent of exchange across the mantle's transition zone remains debated.
Lithosphere: Earth's rigid outer shell, consisting of the crust and the uppermost mantle. The mantle's cool, rigid top joins the crust to form this shell.
Radiogenic heating: Heat produced when radioactive isotopes decay inside Earth and other bodies. Decay of uranium, thorium, and potassium supplies part of the mantle's internal heat.
Subduction: The descent of one tectonic plate beneath another into Earth's mantle. Subduction carries oceanic crust and water into the mantle, changing its composition and flow.
Planetary differentiation: The separation of a forming planet into layers of different compositions and densities. Early differentiation concentrated metal in the core and left silicate material in the mantle.
Mantle heterogeneity: The variation in composition and physical properties among regions of Earth's mantle. Chemical differences in mantle-derived rocks complicate models of long-term circulation.

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