The Rio Grande Rift Zone/Tularosa Basin

December 16, 2013


TularosaBasinNMrte82 Sept013_5

Photographer: Thomas McGuire
Summary Author: Thomas McGuire

The Rio Grande River flows south through a series of broad valleys in southern Colorado and through New Mexico. Here, Earth’s crust is being pulled apart a rate of approximately 1/4 in (5 mm) per year by a rising plume within Earth’s mantle. This is North America's equivalent of the East Africa Rift Zone, which geologists predict may open a new ocean basin. Such spreading of Earth's lithosphere is common under the oceans where rifts encircle Earth like the seams on a baseball, but not common on the continents.

The Tularosa Basin portion of the rift valley, visible in these images, occupies a broad graben. The valley floor has subsided thousands of feet, and partially filled with sediment to become a closed drainage basin. It’s bounded by faults along the Sacramento Mountains on the east (in the foreground) and New Mexico's San Andreas Mountains, visible to the west. White Sands National Monument, the world's largest field of gypsum sand dunes, is visible as a white blotch in the distance.

Will the Rio Grande Rift Zone continue to expand and split North America apart, or will it die out become a failed rift? The answer should become clearer in the next million years or so.

Photo Details: Top photo was taken on September 24, 2013, from the top of the Ski Apache Lookout Mountain, showing the broad basin. Bottom photo was taken on September 25, 2013, along US Rt 82 at the eastern (Alamogordo) boundary fault. Top: Camera: Canon PowerShot SX50 HS; Focal Length: 4.3mm; Aperture: f/4.0; Exposure Time: 0.0016 s (1/640); ISO equiv: 80. Bottom: same except - Exposure Time: 0.0013 s (1/800).