The churning metal of the outer core creates and sustains Earth's magnetic field. The hottest part of the core is actually the Bullen discontinuity, where temperatures reach 6,000° Celsius (10,800° Fahrenheit)—as hot as the surface of the sun. The inner core is a hot, dense ball of (mostly) iron.Aug 17, 2015
There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.
— The spinning iron core in the center of the Earth would stop too. Without the spin, Earth's protective magnetic field would be gone too. The Sun radioactive rays would automatically kill anything left.Jun 16, 2014