This concept became known as uniformitarianism and can be summarized by the phrase "the present is the key to the past." It was a direct rejection of the prevalent theory of the time, catastrophism, which held that only violent disasters could modify the surface of the earth. Today, we hold uniformitarianism to be true and know that great disasters such as earthquakes, asteroids, volcanoes, and floods are part of the regular cycle of the earth.
We find no vestige of a beginning, no prospect of an end. (James Hutton, 1785)
Hutton based the theory of uniformitarianism on the slow, natural processes that he observed on the landscape. He realized that, if given enough time, a stream could carve a valley, ice could erode rock, sediment could accumulate and form new landforms. He speculated that millions of years would have been required to shape the earth into its contemporary form.
Unfortunately, Hutton was not a very good writer. While his paper of 1785 suggested an entirely new theory of geomorphology (the study of landforms and their development), it was the 19th century scholar Sir Charles Lyell whose Principles of Geology (1830) popularized the concept of uniformitarianism.
The earth is estimated to be approximately 4.55 billion years old and the planet has certainly had enough time for slow, continuous processes to mold and shape the earth (including the tectonic movement of the continents around the globe). However, we also know that disasters have a profound impact on the landscape.
In 1994, the U.S. National Research Council stated:
It is not known whether the relocation of materials on the surface of the Earth is dominated by the slower but continuous fluxes operating all the time or by the spectacular large fluxes that operate during short-lived cataclysmic events. (Davis, 18)
The rain from a storm slowly erodes the soil, wind moves sand in the Sahara desert, floods change the course of a river, and uniformitarianism unlocks the keys to the past and the future in what occurs today.
For More Information
Davis, Mike. Ecology of Fear: Los Angeles and the Imagination of Disaster.
Lyell, Charles. Principles of Geology.
Tinkler, Keith J. A Short History of Geomorphology. Barnes & Noble Books, 1985.