The outer core is a liquid layer made up of nickel and iron. It lies underneath the mantle and surrounds the inner core. It is around 2,200 km wide and 6,371 km beneath Earth's surface. The outer core is between 7,000 and 9,000 degrees fahrenheit making it a +4,000 degree difference from the inner core. It is a supposed boundary for the inner core, used to control Earth's magnetic field from the metal inner core. It is believed that the outer core can determine the locations of the north and south poles.