New Mexico Museum of Natural History and Science

 

Valles Caldera, Jemez Volcanic Field


Location: Valles Caldera, 35° 35' to 36°, 15' N, 106°, 10' to 106°, 48' W, Sandoval County
Type: Ash-flow caldera, viscous domes, basaltic flows
Age: 14 Ma to 0.04 Ma
Significance:

One of the largest young calderas on Earth; type area for resurgent ash-flow calderas


Composition:

rhyolite



  

 

 

Dr. Larry Crumpler

 

 

 

 

 

Dr. Larry Crumpler

 

 

 

 

 

Bandelier Ashflow Tuff sitting on paleozoic red rock

Photo: Dr. Larry Crumpler

 

 

 

Bandelier Ash Flow Tuff, Rendija Canyon near Los Alamos.

Photo: Dr. Larry Crumpler

 

 

 

 General Summary: The Jemez Volc


- rifting in Jemez Mountains region began 16.5 Ma
-13 to 10 Ma eruptions of basalt and rhyolite along Ca?ada de Cochiti fault zone
- interbedded with basin-fill conglomerate and laharic breccias of Cochiti Formation
- between 10 and 7 Ma basalt and rhyolite erupted 1/2 the volume of the volcanic field
- 7 to 6 Ma eruptions of mixed magmas and sharp reduction in volcanic activity
- renewed basaltic activity at 4 Ma around margins and to east (Cerros del Rio volcanic field)
- Valles Caldera formed during eruption of Tshirege member at 1.12 Ma
- Bandelier Ash-flow Tuff erupted 1.2 Ma
- rhyolite composition
- 70 mi3 of Tshirege member (Note: Mt. St. Helens was 0.5 mi 3)
- two distinct ash flow events make up the Bandelier: Tshirege Member and Otowi Member
- caldera collapse resulting from eruption from upper part of magma chamber
- roof of magma chamber at 5 to 6 km depth
- resurgent doming of the caldera floor occurred during 100,000 yrs period after Valles collapse - due to buoyant rise of the magma chamber after unloading of upper part onto surface
- caldera fill deposits now exposed on summit of Redondo Peak, 1000 m above caldera moat
- after collapse volcanic activity continued with eruption of rhyolite domes
- domes erupted along caldera ring fracture until about 0.04 Ma
- youngest eruption is the 30 to 70 m thick Banco Bonito obsidian flow on SW ring fracture
- Battleship Rock ignimbrite resulted from explosive precursor to Banco Bonito eruption

Although young and morphologically better developed than the Yellowstone caldera, hydrothermal activity in the Valles Caldera is limited. In part this is due to the relatively dryer environment relative to Yellowstone. It is also a function of the slighter greater age of the Valles system. Numerical models of heat transfer by fluid convection around large rhyolite magma chambers shows that the rate of heat loss is great. Unless continued magma injections occur to replace the heat loss, the thermal system will decline. The Valles caldera has been cooling for about 1.1 Ma since the caldera-forming eruption, and 0.5 Ma since the last rhyolite dome eruptions inside the caldera.

 The following table summarizes the estimated thermal output of the three youngest, large ash-flow calderas in the continental Unites States:

 Caldera                                 Thermal Energy                        Age

Yellowstone, WY                               5000 MW                                               0.6 Ma

Long Valley, CA                                180 MW                                                  0.76 Ma

Valles, NM                                          70 MW                                                    1.1 Ma

 

Summary of Thermal Activity

- Hydrothermal activity initiated about 1 Ma
- Concentrated on SW resurgent dome and western ring-fracture areas
- Mostly dilute groundwater heat by high-temperatures at shallow depths
- Result of convective circulation of water over deep,hot central caldera rocks
- Meteoric water recharges the system; 300°C at depth of 2 to 3 km
- Convection in deep reservoir with “vapor cap”
- Liquid-dominated system at depth ascends convectively to 500 to 600 m depth
- Top of system is “vapor capped” by subsurface boiling at about 200°C
- Heats shallow levels that are diluted with groundwater flowing laterally
- Springs are acid-sulfate waters
- Result from condensation of steam and oxidation of H2S to form sulfuric acid
- Mixes with near-surface groundwater flowing from northern and eastern moat basins - Water flows laterally from top of system down hydrologic gradient
- Thermal waters flow down gradient outside of ring fracture in San Diego Canyon
- Vapor cap formed after breaching of SW caldera margin by ancestral Jemez River
- Resulted in draining of intracaldera lakes
- Lowered hydraulic head resulted in drop of maximum elevation of liquid in reservoir

 

 

Dr. Larry Crumpler

 

 


View Valles Caldera in a larger map

 

General References

Goff, F. J. N. Gardner, Baldridge, J. B. Hulen, D. L. Nielson, et al., 1989, Volcanic and hydrother- mal evolution of the Valles caldera and Jemez volcanic field. N. Mex. Bur. Mines Miner. Resour. Mem, 46, 381-434.

Heiken, G., F. Goff, J. N. Gardner, W.S. Baldridge, J. B. Hulen, D. L. Nielson, and D. Vaniman, 1990, The Valles/Toledo caldera complex, Jemez volcanic field, New Mexico. Ann. Rev. Earth Planet. Sci., 18, 27-53.

Lipman, P. W., 1984, The roots of ash flow calderas in western North America: Windows into the tops of granitic batholiths. Jour. geophys. Res., 89, 8801-8841.

Self, S., G. Heiken, M. L. Sykes, K. Wohlethz, R. V. Fisher, and D. P. Dethier, 1996, Field excur- sions to the Jemez Mountains, New Mexico. New Mex. Bur. Mines, Min. Resour. Bulletin 134. 

 

  


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


Explore New Mexico's Volcanoes

New Mexico Volcano Directory
A map of volcanoes and volcanic features around the state, with detailed discussion of each site.

Volcanoes of New Mexico
Return to the introduction