The term for a scientist who studies the Earth's crust is "geologist." Geologists investigate the composition, structure, and processes of the Earth, including studying rocks, minerals, and the history of geological formations. Their work is essential for understanding Earth's past and predicting future geological events, such as earthquakes and volcanic eruptions. Geologists often use field studies, laboratory techniques, and remote sensing to gather data. They also play a vital role in natural resource exploration, environmental consulting, and helping address challenges related to climate change and land use management.