is one of the most basic principles of modern geology
, the belief that fundamentally the same geological processes that operated in the distant past also operate today. Contrasted with catastrophism
, which believes that earth surface features originated suddenly in the past, by radically different geological processes than those currently occurring. In the 18th and 19th centuries, uniformitarianism versus catastrophism was very controversial, since uniformitarianism seemed to be incompatible with the prevailing religious beliefs of the time. Today, however, all mainstream scientists support uniformitarianism. When Scientist discovered that Uniformitarianism and Catastrophism were both correct they created a new theory called Actualism which proposes that Unifromitarianism and Catastrophism are both true.