New Mexico Museum of Natural History and Science

 

Mt. Taylor: Rio Puerco & Other Volcanic Necks


Location: mostly 35° 05' to 35° 37' N, 107° 05' to 107° 15' W, County
Type: Volcanic Necks
Age: Late Pliocene; ~3 Ma to ~2.5 Ma
Significance:

Composition:

 There is no other place on Earth where the interiors of young volcanoes are so well exposed as in the Rio Puerco.Cabezon is one of many massive dark peaks known as volcanic necks that are scattered throughout the Rio Puerco valley between Mesa Chivato and Mesa Prieta on the west and east, and San Luis and I-40 on the north and south. Together with Mesas Chivato and Prieta they are part of the Mount Taylor volcanic field, a cluster of several hundred small volcanoes. A few volcanic necks, including Cerro Alesna, occur on the west side of Mesa Chivato. Other examples around the south mar- gin of the Mount Taylor field include half-sectioned volcanoes (east Grants Ridge) and deeply dissected volcanoes (Cubero volcano).

They are all the near-surface interiors of small volcanoes that are geologically young, yet were deeply dissected when the Rio Puerco cut a valley through the Mount Taylor volcanic field. Backwasting of the lava flows and erosion of the volcanoes them- selves has exposed the complex interiors of many of the small volcanoes.One may see violent events recorded in their complex structure. The eruptions were similar to those that form small scoria cones, such as Capulin or Bandera volcanoes, and in some cases, similar to that which formed Zuni Salt lake or Kilbourne Hole.