Earth's core

Geological cross section of Earth, showing the different layers of the interior. The internal structure of Earth is the spatial variation of chemical and physical properties in the solid Earth. The primary structure is a series of layers: Its mechanical structure is of a rigid lithosphere, a semi-fluid asthenosphere, a rigid mesosphere, a liquid outer core, and a solid inner core. Its chemical structure is of a silicate crust, a ferromagnesian mantle, and an iron-nickel core whose flowing upper portion generates the Earth's magnetic field.

Scientific understanding of the internal structure of Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through Earth, measurements of the gravitational and magnetic fields of Earth, and experiments with crystalline solids at pressures and temperatures characteristic of Earth's deep interior.