Uniformitarianism

Uniformitarianism is the principle that geological processes observable today also operated in the past. It uses present processes to interpret Earth’s history.

Actualism: The geological method of explaining past events through physical processes known to operate in nature. Actualism expresses the process-based reasoning used to interpret geological history.
James Hutton: The Scottish physician and geologist whose work established a foundational account of Earth as shaped by ongoing processes. His observations of erosion and rock formation helped establish the principle’s geological basis.
Catastrophism: The view that major geological features were shaped chiefly by sudden, large-scale events. It contrasts with uniformitarianism’s emphasis on processes familiar from the present.
Deep time: The concept that Earth’s history spans vast durations far beyond ordinary human experience. Slow processes such as erosion imply more time than a short geological chronology allows.
Geomorphology: The study of landforms and the processes that shape them. Geomorphologists use observable erosion and deposition to explain landscapes through time.
Stratigraphy: The study of rock layers, their sequence, and their relationships in time and space. Layer order preserves evidence that present geological principles help interpret.
Theory of the Earth: James Hutton’s 1788 paper arguing that geological processes operating now have shaped Earth over immense periods. This paper gave an early, influential statement of uniformitarian reasoning.
Uniformity of rate: The claim that geological processes have proceeded at broadly constant rates through time. Uniformitarianism does not require geological rates to remain constant.
Charles Darwin: The English naturalist who developed the theory of evolution by natural selection. Darwin used gradual geological change as a model for cumulative biological change.
Fluvial process: The erosion, transport, and deposition of sediment by flowing water. River processes help explain ancient channels and sedimentary deposits.

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