Answer: Diastrophism is an endogenic process and consists of all processes that move, elevate, or build up portions of the earth’s crust. It is the process that brings about changes in the configuration of the surface of the earth. They move, elevate, or build up portions of the earth’s crust owing to the energy emanating from within the earth. This energy is mostly generated by radioactivity, rotational and tidal friction, and primordial heat from the origin of the earth. The process of diastrophic movements is of the following types:

• Orogenic processes: These involve mountain building through severe folding and affecting long and narrow belts of the earth’s crust. This process takes place when tectonic plates collide, separate, or slide along one another. This causes mountain building through severe folding and affects long and narrow belts of the earth’s crust. Some examples of ongoing orogenic processes are the Mediterranean ridge, Andean orogeny, the Himalayan progeny, etc.
• Epeirogenic processes: These processes involve the uplift or warping of large parts of the earth’s crust. They involve a strictly vertical movement of a continent rather than horizontal movement and also uplifting or warping large parts of the earth’s crust. These processes lift the whole region evenly and result in the formation of gentle arches and structural basins.
• Plate tectonics: These involve horizontal movements of crustal plates. The outer shell of the earth i.e., the lithosphere is broken up into tectonic plates. Plates are classified as major, minor, and micro. Plate tectonics is simply the process of horizontal movement of these plates. The current physical map of the world with the distribution of continents and oceans is the result of the plate tectonic process.
• Earthquakes: They involve relatively local minor movements. Earthquakes occur when the surplus accumulated stress in rocks in the earth’s interior due to folding, faulting, or other physical changes is relieved through the weak zones over the earth’s surface in the form of kinetic energy (seismic waves). Such movements may result in uplift or subsidence in coastal areas.

Through the processes of orogeny, epeirogeny, earthquakes, and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure, volume, and temperature (PVT) changes which in turn induce the metamorphism of rocks.