How does the earth's core generate heat?
The Earth's core contains many metallic elements. Some of them are heavy and radioactive, such as uranium and thorium. As they decay through radioactivity, they release heat and other forms of radiation into the Earth. The heat produced is thought to have driven plate tectonics for billions of years.
There is also some remnant heat left in the Earth's core. This heat was left over from the planet's fiery formation.