The Earth's inner core is roughly 750 miles thick and it is primarily composed of iron. The iron in the Earth's core reaches temperatures as high as 13,000 degrees Fahrenheit, but remains a solid because of the intense surrounding pressure from Earth's outer layers. The ball-shaped concentration of iron that is the Earth's inner core is always moving, causing all of the planet to be magnetic.
The Earth's inner core is directly beneath the mantle, which is a layer that consists of semi-solid minerals and rocks and a sheet of hot magma. The Earth's crust borders the mantle and is the outer most layer on the planet. The crust is a solid layer that is responsible for supporting all forms of biological life on Earth.
The inner core of the planet is thought to be roughly the same temperature as the surface of the Sun, approximately 9,800 degrees Fahrenheit. The tremendous pressure of the outer core, mantle and crust, however, prevents the inner core from transitioning to a liquid or gas at that temperature. The rotation of the inner core acts as a dynamo, creating the Earth's magnetic field that protects it from the effects of the solar wind.