Earth's inner core

Earth's inner core is the innermost <a href="/facts/Internal_structure_of_Earth/678dYXU7">geologic layer</a> of the planet <a href="/facts/Earth/HLLmDfj0">Earth</a>. It is primarily a <a href="/facts/Solid/hj5UsXno">solid</a> <a href="/facts/Ball_(mathematics)/f9vpMVMp">ball</a> with a <a href="/facts/Radius/9Gr9deYD">radius</a> of about 1,220 km (760 mi), which is about 20% of Earth's radius or 70% of the <a href="/facts/Moon/zKHqEMPb">Moon</a>'s radius.
There are no samples of the core accessible for direct measurement, as there are for <a href="/facts/Earth%2527s_mantle/l9DjRLcc">Earth's mantle</a>. The characteristics of the core have been deduced mostly from measurements of <a href="/facts/Seismic_waves/1JTeLfac">seismic waves</a> and <a href="/facts/Earth%2527s_magnetic_field/73G36wmx">Earth's magnetic field</a>. The inner core is believed to be composed of an <a href="/facts/Iron%25E2%2580%2593nickel_alloy/dqyln0KA">iron–nickel alloy</a> with some other elements. The temperature at its surface is estimated to be approximately 5,700 K (5,430 °C; 9,800 °F), about the temperature at the surface of the <a href="/facts/Sun/CadPCVHh">Sun</a>.
The inner core is solid at high temperature because of its high pressure, in accordance with the <a href="/facts/Simon-Glatzel_equation/AfWwlv9j">Simon-Glatzel equation</a>.

Earth's inner core open-in-new

Earth's inner core