Earth's core

Earth's central metallic region consists of a liquid outer core surrounding a solid inner core. Its motion generates the planet's magnetic field.

Geodynamo: The process by which fluid motion and electrical conduction generate a planet's magnetic field. Convection and Earth's rotation organize outer-core flow into magnetic-field-generating motion.
Iron: A chemical element and metal that is Earth's most abundant core constituent. Its high density and abundance make it central to models of core composition.
Planetary differentiation: The separation of a forming planet into layers of different composition and density. Dense metal sank inward during this process to form Earth's core.
Earth's inner-core superrotation: The proposed faster-than-mantle rotation of Earth's inner core, whose rate and persistence remain debated. Seismic observations have not settled how the inner core moves relative to the rest of Earth.
Outer core: Earth's liquid layer of iron-rich metal surrounding the solid inner core. Its electrically conducting fluid circulates and sustains the geodynamo.
Nickel: A metallic chemical element commonly alloyed with iron in meteorites and planetary cores. It is thought to accompany iron in Earth's metallic core.
Giant impact hypothesis: The leading explanation that the Moon formed from debris after a large body struck the early Earth. The impact and ensuing planetary evolution shaped conditions during Earth's early differentiation.
Earth's inner-core anisotropy: The directional variation in seismic-wave speed through Earth's inner core. Its pattern may reveal how inner-core crystals formed and are arranged.
Inner core: Earth's solid, mostly iron central sphere, surrounded by the liquid outer core. It crystallizes as the core cools, releasing heat and buoyant material.
Alloy: A material made by combining a metal with one or more other elements. Core metal is an alloy whose minor elements affect melting and density.

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