What type of geological structure is formed by brittle deformation, leading to movement across a fracture?

The formation of a fault is a result of brittle deformation, which occurs when rocks break rather than bend under stress. In geological terms, a fault is characterized by the movement of rock masses across a fracture zone. This movement can be horizontal, vertical, or a combination of both, depending on the type of fault and the stress that created it.

Faults are significant in geology because they often indicate the history of tectonic forces acting on the Earth's crust. They can also be points of weakness where earthquakes frequently occur, as the stress accumulated in the rocks on either side can eventually be released as seismic energy. The distinction of faults from other geological structures lies in their associated movement and the nature of the fracture; while joints are fractures without movement, faults specifically involve the displacement of rocks. Therefore, the identification of a geological structure as a fault underscores the important processes of brittle deformation and rock movement.