Rio Grande Rift

The Rio Grande Rift is a rift valley[?] extending north from Mexico, near El Paso, Texas through New Mexico into central Colorado. The area is presently quiescent, but significant geologial activity has occurred in the area over the last 20 million years. The Sangre de Cristo[?] Range lies to the east of the north portion of the rift. The Colorado Plateau[?], to the west, includes the San Juan Volcanic Field[?] and the San Juan Mountains. The Rio Grande river follows the course of the rift from southern Colorado to El Paso.