Regional tectonics is the scientific study of the deformation of the rocks that make up the Earth's regions crust and the forces that produce such deformation. It deals with the folding and faulting associated with mountain building; the large-scale, gradual, upward and downward movements of the crust; and sudden horizontal displacements along faults. Other phenomena studied include igneous processes and metamorphism.
Regional tectonics also deals with problems of tectonic subdivision on the basis of data obtained from geologic surveys and through various geophysical methods (primarily seismological methods). The largest structures are rooted in the upper mantle and are called abyssal; examples are the continental cratons and the oceanic, geosynclinal, and orogenic mobile belts. Abyssal structures contrast with crustal structures, which are localized in the crust.