Rio Grande rift

The Rio Grande rift has been an important site for humans for a long time, because it provides a north–south route that follows a major river.

The Rio Grande follows the course of the rift from southern Colorado to El Paso, where it turns southeast and flows toward the Gulf of Mexico.

Important cities, including Albuquerque, Santa Fe, Taos, Española, Las Cruces, El Paso, and Ciudad Juárez, lie within the rift.

The Rio Grande rift represents the easternmost manifestation of widespread extension in the western U.S. during the past 35 million years.

The rift's northern extent is delineated by the upper Arkansas River basin between Leadville and Salida, Colorado.

[3] In cross-section, the geometry of the basins within the rift are asymmetrical half-grabens, with major fault boundaries on one side and a downward hinge on the other.

[11] This intrusion of the asthenosphere into the lithosphere and continental crust is thought to be responsible for nearly all of the volcanism associated with the Rio Grande rift.

[1][2] The Rio Grande rift is intersected in northern New Mexico by the NE-SW trending Jemez Lineament which extends well into Arizona.

[15][16] The Socorro, New Mexico, region of the central rift hosts an inflating mid-crustal sill-like magma body at a depth of 19 km that is responsible for anomalously high earthquake activity in the vicinity, including the largest rift-associated earthquakes in historic times (two events of approximately magnitude 5.8) in July and November 1906.

The fundamental change in the western margin of the North American plate from one of subduction to a transform boundary occurred during Cenozoic time.

The Farallon plate continued to be subducted beneath western North America for at least 100 million years during Late Mesozoic and early Cenozoic time.

[26] There is evidence that the second period of extension began earlier in the central and northern Rio Grande rift than in the south.