Uniformitarianism is the view that the forces affecting the universe are the same now as at any time in the past. It was proposed by geologist Charles Lyell, and was a major influence on Charles Darwin. 
Although uniformitarianism has been geological dogma since the time of Lyell, over the last half century, there has been a noticeable shift away from uniformitarianism. This view is in no way inconsistent with the occurrence of events that cause major changes, just as throwing a ball into the air does not contradict the notion of gravity. For example, the widely accepted that the extinction of the dinosaurs was the result of the collision of an asteroid with the Earth is perfectly consistent with uniformitarianism.
The likelihood of this explanation has been underscored by the actual observation of comet Shoemaker-Levy hitting the planet Jupiter in 1994. This event made huge marks on Jupiter that could be seen by amateur astronomers with backyard telescopes. It has also been underscored by the recent realization that large numbers of asteroids come surprisingly close to Earth.
- Catastrophism, a theory opposing uniformitarianism.
- Wile, Dr. Jay L. Exploring Creation Through General Science. Anderson: Apologia Educational Ministries, Inc. This idea has been widely criticized by many for the lack of evidence backing it. 2000