Internal structure of Earth

Earth has a thin silicate crust, a thick mantle, and a metallic core. Their composition, temperature, pressure, and physical state vary with depth.

Earth's crust: Earth’s thin, rigid outer layer of solid silicate rock, divided into continental and oceanic crust. The crust is the outermost compositional layer and the surface platform above the mantle.
Seismic wave: An elastic disturbance that travels through Earth or along its surface, carrying energy from an earthquake. Changes in wave speed and path expose internal boundaries and material properties.
Richard Dixon Oldham: A British geologist who identified distinct seismic-wave paths and inferred Earth’s core in 1906. His analysis provided early seismic evidence for a deep internal boundary.
Geodynamo: The process by which motion of electrically conducting liquid in a planet’s interior generates a magnetic field. Convection in the liquid outer core powers Earth’s global magnetic field.
Earth's inner-core rotation: The rotation of Earth’s solid inner core relative to the mantle and crust. Seismic observations continue to refine how the innermost layer moves.
Earth's mantle: The thick silicate-rock layer between Earth’s crust and core, mostly solid but capable of slow flow. It accounts for most of Earth’s volume and drives large-scale interior circulation.
Mohorovičić discontinuity: The seismic boundary between Earth’s crust and mantle, marked by a sharp increase in seismic-wave speed. This discontinuity locates the compositional transition beneath the crust.
Andrija Mohorovičić: A Croatian seismologist who identified the crust–mantle boundary from earthquake-wave arrivals in 1909. His observations established the discontinuity now named for him.
Earth's magnetic field: The magnetic field surrounding Earth, generated primarily by motion in its liquid outer core. The core’s physical state and circulation account for this field.
D'' layer: A heterogeneous region at the base of Earth’s mantle, immediately above the core–mantle boundary. Its complex structure may record interactions between the mantle and core.

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