Earth磗 internal structure, animated model. The main layers of the Earth peel off in sequence. First the crust opens to reveal the underlying mantle. The crust is around 40 kilometres thick in the continents, and as little as 5 kilometres thick in the deep ocean. Beneath the crust is the mantle orange, a viscous layer of rock some 2900 kilometres deep. Beneath that is the outer core yellow, which is a liquid composed of molten iron and nickel. Convection currents in these metals are responsible for producing the Earth磗 magnetic field. The outer core in around 2250 kilometres thick. Below it is the solid inner core white, which is a hot, solid sphere of iron and nickel, some 1200 kilometres in radius, at a temperature of around 5500 degrees Celsius.