Mt. Taylor: Volcanic Necks

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

Verical erosion through a classic volcanic field; near surface structure of scoria cones and maars


Alkali basalt


Dr. Larry Crumpler



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 margin 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 themselves 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.



Photo taken by Jayne Aubele



Photo taken by Dr. Larry Crumpler


Cerro Alesna is an unusual volcanic neck on the west side of the Mount Taylor volcanic field. Unlike most of the dark and craggy necks in the Rio Puerco Valley, Cerro Alesna has huge sweeping massive columns. This is an difficuylt volcanic neck to approach because of land access issues. But I suspect that it consists of an unusual type of volcanic rock, trachyte, benmoreite, or possibly mugearite,  that makes the adjacent Mount Taylor volcanic field really unique and rather odd on the North American continent. These rocks types erupt rather viscously and tend to form large lava domes on Mesa Chivato, the part of the Mount Tayloir field due east of Alesna.

Photo taken by Dr. Larry Crumpler


East Grants Ridge (Half section scoria cone). Where else can you see a scoria cone naturally cross-sectioned? And to make the picture easier to see, the cone and its dark scoria sit on top of brilliant white ignimbrites from a nearby earlier rhyolite dome. The massive basaltic "plug" is actually more of a cork. It narrows down to a small dike only a meter or two wide at its base.The whole thing is like soemthing out of a volcanology textbook. It is the Grants, New Mexico "Mount Rushmore"! It is right next to the paved road in Lobo Canyo. This is a highlight for the volcano tourist.

Photo taken by Dr. Larry Cumpler


Rio Puerco dike

Photo Taken by Dr. Larry Crumpler



New Mexico Centennial Stamp (Santa Clara and Cerro Guadalupe)



Sun behind Cerro Guadalupe



Annular Eclipse, May 20, 2012, through Cerro Guadalupe



Santa Clara

Photo taken by Dr. Larry Crumpler


Santa Clara Aerial

Photo Taken by Dr. Larry Crumpler


View the  Mt. Taylor Volcanic Necks in a larger map



All text and photo credit due to Dr. Larry Crumpler, New Mexico Museum of Natural History and Science

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