The Earth's interior is composed of four layers, three solid and one liquid—not magma but molten metal, nearly as hot as the surface of the sun. The deepest layer is a solid iron ball ...

Earth's innermost layer is called the core. The outside of Earth's core is made from molten nickel and iron that can reach temperatures of 9,000 degrees Fahrenheit (5,000 degrees Celsius).

Sinking in one place leads to plates moving apart in other places. The movement of the plates and the activity inside the Earth, is called the theory of plate tectonics.