Basic Geology/Outer Core
The outer core of the Earth is a liquid layer about 2,260 km thick composed of iron and nickel which lies above the Earth's solid inner core and below its mantle. Its outer boundary lies approximately 2,890 km (1,800 mi) beneath the Earth's surface. The transition between the inner core and outer core is located approximately 5,150 km beneath the Earth's surface.
The temperature of the outer core ranges from 4400 °C in the outer regions to 6100 °C near the inner core. Eddy currents in the nickel iron fluid of the outer core are believed to influence the Earth's magnetic field. The outer core is not under enough pressure to be solid, so it is liquid even though it has a composition similar to that of the inner core. Sulfur and oxygen could also be present in the outer core.
Without the outer core, life on Earth would be very different. Scientists believe that the convection of liquid metals in the outer core creates the Earth's magnetic field. This magnetic field extends outward from the Earth for several thousand kilometers, and creates a protective bubble around the Earth that deflects the Sun's solar wind. Without this field, the solar wind would have blasted away our atmosphere, and Earth would be lifeless like Mars.