Cutaway artwork showing the internal structure of the Earth. Below the outer rocky layer (lithosphere), a zone of near-molten rock called the mantle (red) extends down to 2900 kilometers (km). Mantle material rises to form new lithosphere at mid-ocean ridges. Lithosphere sinks into the mantle in subduction zones and is destroyed. As the pressure increases with depth, the mantle thickens and its temperature rises to an estimated 3000 degrees Celsius. Beneath the mantle is the nickel-iron core. It is about 7000 km across. The outer core (dark yellow) is molten and the inner core (bright yellow) is solid. The temperature at the core may be over 5000 degrees Celsius.