The mantle is the layer of the Earth that lies between the outer core and the crust. It is primarily composed of solid rock, but it can behave as a viscous fluid over long timescales due to its high temperature and pressure. The mantle plays a crucial role in the movement of tectonic plates, which leads to earthquakes, volcanic activity, and the formation of mountain ranges. Research on the mantle involves studying its composition, structure, dynamics, and interactions with other Earth systems. Understanding the mantle is important for predicting geological hazards, interpreting the history of Earth's evolution, and exploring the potential for natural resources.