Folding and Faulting Crustal displacement produced by plate movement , subduction , volcanic activity , and intrusive igneous activity can create huge stresses within the Earth's crust. In some cases, these stresses can cause folding and faulting to occur within the Earth's rocks. A fold can be defined as a bend in rock.
Folds are most visible in rocks that contain layering.
The higher the temperature of the rock the more plastic it becomes. Pressure must not exceed the internal strength of the rock. If it does, fracturing occurs. Deformation must be applied slowly. A number of different folds have been recognized and classified by geologists.