Earth's inner core

Innermost part of Earth, a solid ball of iron-nickel alloy

Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,230 km (760 mi), which is about 20% of Earth's radius or 70% of the Moon's radius. As recently as February 2025 there are indications that the previously believed solid iron-nickel sphere is partially deformable and undergoing viscous changes.

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