Internal Structure of Earth When large earthquakes occur, they generate strong seismic waves that refract and reflect as it travels through the layers of the planet. These waves are detected and recorded by seismographs all around the world.             Image credit: [3]

The Inner Core 70% of the size of the moon and as hot as the surface of the Sun. Solid and growing: Heavy constituents freeze to the inner core boundary. Releasing latent heat into the fluid outer core. Also, solidification of iron leaves behind buoyant fluid of light constituents. Spinning faster than the mantle by 1 to 3 degrees per year faster. Angular velocity affected by viscous and magnetic torques. The Outer Core Conductive molten material of mostly iron and nickel. A unique system that is cooled from the top but freezes from the bottom since the melting temperature increases with pressure more rapidly than the temperature along the adiabat. Local fluxes of light constituents are proportional to fluxes of latent heat released from the inner core and provide three times more buoyancy than the heat. Superrotation: Inner core boundary rotates faster than core-mantle boundary. In reference to the mantle, the inner core drives a flow in the outer core. The viscous forces in the bulk fluid core are assumed to be about five orders of magnitude smaller than the Coriolis and Lorentz forces.