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Desert Diary
Fossils/Rift Valley


The Great Rift Valley of Africa is world famous, but many people don't know why it's called a rift valley—and don't realize we have a counterpart in the northern Chihuahuan Desert. These valleys are formed when titanic forces acting far beneath the earth's surface slowly rip apart the planet's crust. As the resulting chasm develops, vast blocks of bedrock sink into it, forming a deep valley that rapidly fills with sediments from highlands on either side. Molten rock often makes its way to the surface along the shattered edges, to emerge as volcanos.

In our region, the Rio Grande Valley is formed from a linear cleft extending from southern Colorado south to at least El Paso. Geologists recognize this as the aptly named Rio Grande Rift. It formed by tearing asunder lands to the east and west, which move slowly apart over many millions of years. The classic signs are all there: deep, nearly linear basins, tilted mountain blocks rimming the valley, and volcanos strung like beads on either side of the rift.
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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.