The Earth's mantle is a thick layer of rock located between the Earth's crust and the outer core. It extends about 2,900 kilometers (1,800 miles) deep and is composed mainly of silicate minerals rich in iron and magnesium. The mantle is semi-solid, allowing it to flow slowly over time, which plays a crucial role in the movement of tectonic plates. This layer is divided into the upper and lower mantle. The upper mantle is partially molten and interacts with the Earth's crust to create geological features like volcanoes and mountains. The lower mantle, being denser and hotter, is more rigid and extends down to the outer core.