scientific study of landforms and the processes that shape them
Geomorphology  is the scientific study of landforms and the processes that shape them.
More broadly, it studies the evolution of the topography of a planet. Geomorphologists seek to understand why landscapes look the way they do, to understand landform history and dynamics, and to predict future changes. They use a combination of field observation, physical experiment, and numerical modeling.
Geomorphology is part of geography, geology, geodesy, engineering geology and archaeology. This range of interests leads to a wide variety of research styles and interests in the field.