According to National Geographic, the outer core of the Earth is 2,300 kilometers (1,430 miles) thick. The outer core is mostly composed of iron and nickel and retains a temperature between 4,000 and 5,000 degrees Celsius.
The Earth has three distinct levels: the crust, the mantle and the core. The outer level, or crust, is where all life resides. It is also the thinnest of the three layers. The mantel is the thickest section and is made up of mostly rocks and other minerals. When the mantel shifts, tectonic events like earthquakes and volcanic eruptions occur on the crust. The core lies beneath the mantle and is divided into two sections, the outer and inner core. These two sections are made up of mostly metal.