In geology, a massif ( /mæˈsiːf/ or /ˈmæsɪf/) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a group of mountains formed by such a structure. In mountaineering and climbing literature, a massif is frequently used to denote the main mass of an individual mountain. The massif is a smaller structural unit of the crust than a tectonic plate and is considered the fourth largest driving force in geomorphology.