The inner core is the very center of the Earth. It is a 1250 km, or about 776 miles, thick ball of solid iron and nickel. It burns at 9032 degrees fahrenheit, but because of all the pressure of the Earth, like the layers of rock and metal and the Earth's mountains, the iron cannot stay in a liquid state. Therefore the inner core never melts.
The Outer Core
The outer core is the next layer, it wraps around the inner core. It is made of liquid iron and nickel. It is around 2200 km, or 1367 miles, thick and it's temperature is 8132 degrees fahrenheit. Because it is under slightly less pressure than the inner core, the very high temperature makes it molten.
