Earth’s core composition

Earth’s core is mostly iron and nickel. Which lighter elements are mixed in, and in what amounts? Earthquake waves, or seismic waves, travel through the planet, giving clues to how its deep material behaves. But different mixtures can resemble one another in those measurements.[1] [2] [4]

Earth’s iron-rich core contains lighter elements, but neither their amounts nor their distribution between the solid inner core and liquid outer core is uniquely known. Which mixture fits the observations and the core’s history? Earthquake waves constrain elastic behavior: how material responds to deformation. Chen and colleagues’ 2026 calculations find many iron mixtures, or alloys, with compatible density and wave speeds, so those fits cannot select one composition. Freezing supplies an additional test. A first stable crystal must form in the liquid, a process called nucleation; cooling below the melting temperature may be needed before this happens. Wilson and colleagues’ iron–carbon simulations test that requirement, rather than measure the core’s ingredients directly.[2] [3] [4]

The solid inner core and liquid outer core are known; their exact chemical mixtures are not.[1] [2]

The 2026 inner-core calculations admit multiple compatible alloys. The 2025 iron–carbon freezing result adds a possible nucleation route, rather than a unique chemical reconstruction.[2] [3]

Changing the mixture changes how core material freezes and carries heat. Those effects influence the growth of the solid inner core and the motion of liquid metal around it, which sustains Earth’s magnetic field.[3]

Composition links freezing and heat loss to the liquid-core motion that sustains Earth’s magnetic field.[3]