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An Ongoing Process

As rocks continue to wear away, more unconformities appear. As road crews cut through mountains, they expose unconformities for the speeding motorist as well as the geologist to enjoy. However, these new exposures and the mountains that contain them will erode flat. The Appalachians, the Himalayas, the Alps, the Rockies, even the Grand Canyon, will die their slow erosional deaths as nature levels the continents, which may then subside beneath the seas. However, more sediment will soon accumulate, which will uplift and erode, and so on into eternity—an unbroken cycle of geologic processes.

See also Geologic time.



Baars, Donald L. The Colorado Plateau: A Geologic History. Albuquerque: University of New Mexico Press, 1983.

Chronic, Halka. Pages of Stone: Geology of Western National Parks and Monuments. Vol. 4. Grand Canyon and the Plateau Country. Seattle: The Mountaineers, 1988.

Chronic, Halka. Roadside Geology of Arizona. Missoula, MT: Mountain Press, 1984.

Dixon, Dougal, and Raymond L. Bernor, ed. The Practical Geologist. New York: Simon and Schuster, 1992.

Harris, Ann G., Esther Tuttle, and S. D. Tuttle. Geology of National Parks. 4th ed. Dubuque: Kendall/Hunt Publishing Co., 1990.

McPhee, John. Basin and Range. New York: Farrar, Strauss & Giroux, 1982.


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Angular unconformity

—An unconformity, or gap, in the rock record, where horizontal rock layers overlie tilted layers.


—An unconformity, or gap, in the rock record, situated between parallel rock layers.


—An unconformity, or gap, in the rock record, where sedimentary rocks overlie metamorphic or igneous rocks.

Additional topics

Science EncyclopediaScience & Philosophy: Two-envelope paradox to VenusUnconformity - Angular Unconformities, Disconformity, Nonconformities, An Ongoing Process