The rocks at the core of the Earth are believed to be rich in iron and nickel. This is because scientists have studied the behavior of seismic waves passing through the Earth and have observed that they change their speed and direction when they encounter different materials. By analyzing these changes, scientists have determined that the Earth has a solid inner core and a liquid outer core. The outer core is thought to be composed of a mixture of molten iron and nickel, while the inner core is thought to be a solid ball of iron and nickel. This is supported by the fact that meteorites, which are believed to be remnants from the early solar system, also contain high amounts of iron and nickel.