An Etymological Dictionary of Astronomy and Astrophysics

The innermost part of the Earth consisting of a solid → inner core, mainly composed of → iron, and a → liquid → outer core. The → pressure and → temperature are so extreme that the molten iron solidifies. The temperature at the inner core boundary is expected to be close to the
→ melting point of iron at 330 gigapascal (GPa). From static laser-heated diamond anvil cell experiments up to 200 GPa, using synchrotron-based fast → X-ray diffraction as a primary melting diagnostic, S. Anzellini et al. (2013, Science 340, 484)
conclude that the melting temperature of iron at the inner core boundary is 6230 ± 500 K. This estimation favors a high heat flux at the core-mantle boundary with a possible partial melting of the → mantle. The inner core, 2,400 km in diameter, is suspended in the molten metal of the → outer core, which is about 2,240 km thick. The temperature difference between the mantle and the core is the main engine for large-scale thermal movements, which coupled with the → Earth’s rotation, function as a generator for the planet’s → magnetic field.

See also: → Earth; → core.