Core–mantle boundary

The interface about 2,900 kilometers beneath Earth’s surface separating the silicate mantle from the metallic outer core. It marks sharp changes in seismic properties, composition, and heat flow.

Dʺ layer: A heterogeneous region at the base of the mantle, immediately above the core–mantle boundary. Its seismic structure records complex conditions directly above the boundary.
Earth's mantle: The thick silicate-rock layer between Earth’s crust and metallic core. It forms the rocky side of the interface.
Andrija Mohorovičić: A Croatian seismologist who discovered the boundary between Earth’s crust and mantle. His crust–mantle discontinuity contrasts with the much deeper core–mantle interface.
Large low-shear-velocity provinces: Vast regions above the core–mantle boundary where shear waves travel unusually slowly. Their origins and composition remain disputed despite their striking seismic signatures.
Seismic discontinuity: A depth within a planet where seismic-wave velocities or paths change abruptly. The boundary is a major discontinuity in seismic-wave speed and density.
Earth's outer core: A liquid iron-rich layer surrounding Earth’s solid inner core. It forms the metallic, liquid side of the interface.
Inge Lehmann: A Danish seismologist who discovered Earth’s solid inner core in 1936. Her seismic reasoning helped establish the layered structure surrounding the boundary.
Ultra-low-velocity zone: A thin region at the base of the mantle where seismic-wave speeds drop sharply. It may contain partial melt or unusual iron-rich material at the interface.
Seismic tomography: A method that reconstructs Earth’s interior structure from seismic-wave observations. Tomographic images map hot and cold mantle structures approaching the boundary.
Earth's inner core: Earth’s solid central region, composed mainly of iron and nickel. Its growth influences heat and compositional circulation in the outer core below the boundary.

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