The inner core has a radius of about 1,220 km, which is about 20% of Earth's radius. Information about Earth's core mostly comes from analysis of seismic waves and Earth's magnetic field. The temperature at the inner core's surface is estimated to be approximately 5,700 K, which is about the temperature at the surface of the Sun.

The outer core begins approximately 2,889 km beneath Earth's surface at the core-mantle boundary and ends 5,150 km beneath Earth's surface at the inner core boundary.

The mantle has a mass of 4.01 × 1024 kg and thus makes up 67% of the mass of Earth. It has a thickness of 2,900 kilometers making up about 84% of Earth's volume. It is predominantly solid but on geologic time scales it behaves as a viscous fluid, sometimes described as having the consistency of caramel.  

Earth's layers can be classified as compositional (crust, mantle, and core) or as mechanical (lithosphere, asthenosphere, mesosphere, outer core, and inner core). The crust is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The lithosphere is broken into tectonic plates whose motion allows heat to escape from the interior of Earth into space.