In 1908 over Tunguska, Russia, an object that is believed to have been either a comet or a stony meteorite exploded with the force of a nuclear bomb. If it had happened over an urban area instead of over Siberian wilderness, the loss of life would have been immense. AP/Wide World. Reproduced by permission.

Catastrophism is the argument that Earth's features—including mountains, valleys, and lakes—primarily formed and shaped as a result of the periodic but sudden forces as opposed to gradual change that takes place over a long period of time.

Although geologists may argue about the extent of catastrophism in shaping the earth, modern geologists interpret many formations and events as resulting from an interplay catastrophic and uniform forces that result in more slowly evolving change.

For example, according to strict catastrophe theory, one might interpret the origins of the Rocky Mountains or the Alps...