The mantle is a layer of the Earth located between the outer crust and the outer core. It is composed mainly of silicate rocks that are rich in iron and magnesium. The mantle extends to a depth of about 2,900 kilometers (1,800 miles) and plays a crucial role in the movement of tectonic plates, which are responsible for earthquakes and volcanic activity. The mantle is divided into the upper and lower mantle. The upper mantle is partially molten, allowing for convection currents that drive plate tectonics. The lower mantle, on the other hand, is solid but behaves like a viscous fluid over long periods, contributing to the dynamic nature of the Earth's interior.