Catastrophism
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, as resulting from a huge earthquake that uplifted them quickly. When viewing the Yosemite Valley in California a catastrophist might not assert they were carved by glaciers, but rather the floor of the valley collapsed over 1,000 ft (305m) to its present position in one giant plunge. Strict catastrophic theory also argues for long periods of inactivity following catastrophic events.
In terms of modern geoscience, strict catastrophic theory (e.g., a world shaped by large single floods, or massive earthquakes) finds little evidence or support. Catastrophism developed in the seventeenth and eighteenth centuries when, by tradition and even by law, scientists used the Bible and other religious documents as a scientific documents.
For example, when a prominent theologian, Irish biblical scholar Bishop James Ussher in the mid-1600's work, Annals of the World, counted the ages of people in the Bible and proclaimed that Earth was created in 4004 B.C. (In fact, Ussher even pronounced an actual date of creation as the evening of October 22), geologists tried to work within a time frame that encompassed only around six thousand years. (Current research estimates Earth at 4.5 billion years old.) In its original form, catastrophism eventually fell from grace with the scientific community as they reasoned more logical explanations for natural history. A new concept, known as uniformitarianism, eventually replaced catastrophism. Uniformitarianism is the argument that mountains are uplifted, valleys carved, and sediments deposited over immense time periods by the same physical forces and chemical reactions in evidence today.
Modern catastrophism—increasingly popular since the late 1970s—argues evidence that catastrophic forces can have a profound influence on shaping Earth. For example, modern catastrophic theory argues that large objects from space (Asteroids, Comets, etc.) periodically collide with Earth and that these collisions can have profound effects on both the geology and biology of Earth. Based on the extrapolation of experimental data and the observation of large-scale events (e.g., major volcanic eruptions), scientists speculate that when these objects strike, they clog the atmosphere with sunlight-blocking dust and gases, ignite forest fires, and trigger volcanism. One hypothesis advances that a large asteroid impact lead to the extinction of dinosaurs roughly 65 million years ago.
Cambrian Period; Fossil Record; Fossils and Fossilization; Geologic Time; Historical Geology; Impact Crater; K-T Event; Origin of Life; Orogeny; Plate Tectonics; Precambrian; Torino Scale
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