Earth's core.  The interior of the Earth is thought to contain; an inner solid core of iron and nickel, an outer core of molten rock and a mantle made of solid rock. The Earth's crust, which forms the continents and the ocean floor, is between 50 and 65 kilometres thick.

Studies indicate that the earth consists of concentric layers that differ in size, chemistry, and density. The outer shell, or crust, consists of the continents and the ocean basins. The thin, outermost layer of lighter rock is the crust, varying in depth from between 30mi (50km) - the thickest continental crust - to 3 mi (5km) - the thinnest oceanic crust.

Like all the terrestrial planets, there is a dense core rich in iron and nickel, surrounded by a mantle of silicate rocks. The crust and the uppermost mantle together form the lithosphere, consisting of tightly fitting slabs called plates. The crust is broken into vast plates that slide around or float on a plastic zone, or semi-molten layer of mantle called the asthenosphere, within the middle shell, or mantle. These interactions are known as plate tectonics.

At the center of the earth is an outer core, believed to be liquid, and an inner, solid core. The solid inner core rotates at a differenct rate than the molten outer layers, and this causes the Earth's magnetic field.