Uniformitarian interpretation, in geology is the viewpoint that Earth's geologic processes acted in the same manner and with essentially the same intensity in the past as they do in the present and that such uniformity is sufficient to account for all geologic change.
The Uniformitarian viewpoint was formulated in the early 1800's by James Hutton. Scientists at that time believed the earth was less than 10,000 years old, and earth's geology had been formed by a great catastrophic flood. Hutton was opposed to that belief and speculated: "What if earth's geology was not formed quickly by a great flood; what if it formed slowly over a very long period of time through slow natural processes?"
A man who read a book by Hutton on the age of the earth based on slow natural processes was Charles Lyell. Neither Hutton nor Lyell had science degrees. Lyell graduated from law school, practiced law for two years, then read Hutton's book, quit his law practice and devoted his life to studying the rocks and fossils. This is when the field of geology began.
Catastrophism interpretation - is the viewpoint that many of Earth's crustal features (strata layers, erosion, polystrate fossils, etc) formed as a result of past cataclysmic activity - such as a world-wide catastrophic flood.
One thing to be aware of: opposing theories often predict the same evidence.
Much of the clip art on this site is courtesy of Phillip Martin.