Answer:
He is probably studying Geomorphology.
Explanation:
Geology is the science that studies the composition, structure, dynamics, and history of planet Earth, the processes by which it has evolved including everything that has to do with its natural resources and with this the processes that affect the surface, and therefore, the environment.
Geomorphology is a branch of geosciences, more specifically geography and geology. One of his most interesting models explains the ways in which the earth's surface is the result of a consistent dynamic balance.