Inner Core – the dense, solid center of the earth, formed mostly of iron and nickel

Outer core – the liquid layer of the earth’s core that surrounds the inner core and is comprised of iron and nickel

Mantle – the thickest layer inside the earth; it lies between the outer core and the crust and is described as being plastic like; formed mostly of silicon, oxygen, magnesium, and iron

Crust – the outermost layer of Earth, varying in thickness from more than 60 km to less than 5km

Lithosphere – the rigid, outermost layer of earth, about 100 km thick, composed of the crust and part of the mantle

Asthenosphere – the plastic like layer below the lithosphere in the Earth’s mantle