geological formation

Encyclopedia Article


In the study and mapping of the earth's surface, geologists classify a geological formation as any basic unit of rock that stands out from its surroundings. A geological formation, therefore, can be small or very large, but must be distinct in appearance as well as substantial enough to chart on a map. Geological formations are often given names based on their location and their dominant rock type. For example, the El Malpais sandstone bluffs are a unique formation of sandstone, located in the El Malpais National Monument near Grants, New Mexico.

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"Sandstone Bluffs, El Malpais National Conservation Area, NM, May 12, 2010" by Lee is licensed under CC BY-SA.

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