Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 51

The idea that geologic processes we observe today have always been occurring and can be used to explain the features of the earth has stood the test of time. In fact, now more than ever, geologists recognize that the physical, chemical, and biological processes that occur today must have occurred in the past as well. Even a feature as spectacular as the Grand Canyon is created by the same simple process of erosion by water (see Chapter 12) that creates creeks and gullies in your backyard.

However, when Hutton and Lyell proposed the concept of uniformitarianism, they assumed that the rate and intensity of past processes were the same as those observed today. The current understanding of uniformitarianism in geology no longer makes this assumption. Modern uniformitarianism differs from the original idea in two very important ways:

 Rates and intensity of processes may vary: While the processes scientists observe today occurred in the past, they may have occurred more quickly or more intensely than they do now. For example, massive layers of volcanic rocks across Siberia (called the Siberian Traps) suggest a period of very intense lava outpourings, unlike anything humans have ever observed.

 Catastrophes do play a role: When uniformitarianism was first proposed, it ran counter to the ideas of catastrophism. But modern geologists recognize that occasional catastrophic events (such as volcanic eruptions and tsunamis) do play an important role in shaping the earth’s surface.