What geological term describes the changes that occur gradually over time?

The term that describes the changes that occur gradually over time is uniformitarianism. This principle, which is fundamental to the field of geology, suggests that the processes we observe shaping the Earth today, such as erosion, sedimentation, and volcanic activity, have been operating in a similar manner throughout geological history. It supports the idea that understanding current geological processes allows scientists to infer the historical geological events that have shaped the Earth's surface.

Uniformitarianism contrasts with catastrophism, which emphasizes the idea that Earth’s features were shaped by sudden, short-lived, and catastrophic events. Meanwhile, geochronology focuses on dating rocks and geological events, and biostratigraphy deals with the distribution of fossils within sedimentary rocks to date strata. Thus, while these concepts are important in geology, they do not specifically address the gradual nature of geological changes over time as uniformitarianism does.