Earth's internal structure. Cutaway computer artwork showing the different layers that make up the structure of the Earth. The external layer (crust) shows the Earth's surface topography and atmosphere, including land (green), water (blue) and clouds (white). This layer extends downwards for around 35 kilometres. The mantle is divided into the external mantle (dark orange), composed of solid rock (600km) and internal mantle, composed of semi-molten rock (light orange, 2300km). The outer core (brown) is a liquid layer of iron and nickel, around 2160 kilometres thick. The inner core (bronze, centre) is a liquid sphere of iron-nickel alloy, with a radius of 1320 kilometres.