Isostasy is a concept in geology that refers to the equilibrium of the Earth's crust, where the lithosphere floats on the denser, underlying asthenosphere. This balance occurs because of the differing densities of the materials that make up the Earth's crust and mantle. Isostasy plays a crucial role in shaping the Earth's surface, as it influences the distribution of mountains, valleys, and other landforms. Researchers study isostasy to understand the processes that shape the Earth's crust and to interpret geological features like mountain building, erosion, and tectonic movements.