Which principle states that geological changes occur suddenly rather than gradually?

The principle that states geological changes occur suddenly rather than gradually is known as Catastrophism. This theory suggests that the Earth's landscape has been shaped primarily by a series of sudden, short-lived, and violent events, such as volcanic eruptions, earthquakes, and mass extinctions, rather than by the slow and gradual processes emphasized in other geological theories.

Catastrophism was historically significant as it provided an explanation for observed geological phenomena and helped to account for the sudden appearance and disappearance of species in the fossil record. This principle contrasts with the concept of Uniformitarianism, which posits that the processes shaping the Earth today have always operated in the same way over geological time, thus suggesting a more gradual change. Understanding these principles is key for interpreting geological history and the processes that shape our planet.