Earth's outer core is a fluid layer about 2,400 km thick and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle.
The outer core, about 2,200 kilometers (1,367 miles) thick, is mostly composed of liquid iron and nickel. The NiFe alloy of the outer core is very hot, between 4,500° and 5,500° Celsius (8,132° and 9,932° Fahrenheit)
