The name of the layer of the Earth beneath the crust is the mantle. The mantle is composed of semi-solid rock and extends to a depth of about 2,900 kilometers. It plays a crucial role in Earth's geology, as convection currents within the mantle drive plate tectonics. The mantle's movements contribute to volcanic activity, earthquakes, and the creation of mountain ranges. Understanding the mantle is essential for studying plate movements and Earth's dynamic processes.