Geosciences is the study of the Earth, including its formation and chemical, physical and biological aspects. These studies form the basis for improved approaches to issues in natural resources, geohazards, and environmental impacts. Geoscientists also study how the lithosphere interacts with the hydrosphere and atmosphere. The department's renowned Laboratory of Tree-Ring Research uses tree-rings to study climatic, ecological, environmental and archaeological problems. Majors study tectonics, geophysics, geochemistry, geochronology and thermodynamics, seismology, paleobiology, economic geology and quaternary studies, which examines the more recent history of the Earth. Students may concentrate on geology or geophysics. A teaching major is also offered, leading to certification to teach earth sciences in Arizona public schools.

The Earth Systems Science concentration in the Geosciences major provides students with coursework in chemistry, biology, physics, and mathematics, as well as climatology, ocean science, sedimentation, and geomorphology. Graduates in this concentration will be prepared for work as educators, consultants, researchers, and conservation specialists. This concentration also establishes a strong foundation for graduate studies in geosciences, atmospheric sciences, hydrology, arid lands resource sciences, or physical geography.