It is thought that the center of the earth is composed of iron, nickel, and rock, making up the inner core (solid) and outer core (liquid). Above the core is the mantle, which comprises about 80% of the volume of the earth. The mantle is a thick liquid. The very outer layer is the crust, which is a layer of rock. Even at its thickest point, the crust is only 37 miles (60 kilometers) thick.
It is thought that the center of the earth is composed of iron, nickel, and rock, making up the inner core (solid) and outer core (liquid). Above the core is the mantle, which comprises about 80% of the volume of the earth. The mantle is a thick liquid. The very outer layer is the crust, which is a layer of rock. Even at its thickest point, the crust is only 37 miles (60 kilometers) thick.