Volcanic evolution of Mount Taylor Stratovolcano, New Mexico: Facts and misconceptions
— Fraser Goff, William McIntosh, Lisa Peters, John A. Wolff, Shari A. Kelley, Cathy J. Goff, and G. Robert Osburn


Mount Taylor (3445 m elevation) developed from roughly 3.2 to 2.5 Ma and is a composite stratovolcano (Mount Taylor stratovolcano, MTS) composed of coalesced basaltic trachyandesite to rhyolite domes, flows, plugs, dikes, interlayered ash, and comingled debris flows. The main edifice is surrounded by later cones and flows of (mostly) trachybasalt that erupted until 1.27 Ma. Contrary to previous interpretations, the summit trachyandesite flows of MTS (2.75 to 2.72 Ma) are not the youngest eruptions on the edifice. A variety of satellite domes, flows, radial dikes and a central plug of mostly trachydacite were intruded and erupted until 2.52 Ma. Thus, also contrary to previous studies, the youngest eruptions at MTS are not “andesitic.” An elongate, eastward-facing Amphitheater about 6.5 km long formed in the approximate center of MTS late in its development. The best explanation for formation of the MTS Amphitheater is erosion by mass wasting and fluvial incision. This feature did not form from large, centralized, late stage explosions, from Mount St. Helens-type lateral blasts with associated fall and ignimbrite, or from Pleistocene glaciation of the edifice, although it may have formed in part from an unrecognizable debris avalanche. Previous studies have speculated that MTS developed a single cone or bulbous dome that once attained a height of 4270 m, but it is more probable that the mixture of small, coalesced vents and domes forming the original summit never rose above 3800 m. Using this maximum elevation, an average diameter of 16 km for the volcano from recent mapping, and the formula for a right circular cone, the estimated volume of MTS is 85 km3 ±20%. From this volume and the time span of intense MTS construction (0.76 Ma), the average eruptive (magmatic) flux rate is about 0.11 km3 per 103 years. These values for MTS are small compared to those of Cascades-type subduction zone stratovolcanoes, such as Mount St. Helens.

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Recommended Citation:

  1. Goff, Fraser; McIntosh, William; Peters, Lisa; Wolff, John A.; Kelley, Shari A.; Goff, Cathy J.; Osburn, G. Robert, 2021, Volcanic evolution of Mount Taylor Stratovolcano, New Mexico: Facts and misconceptions, in: New Mexico Geological Society, 71st Annual Fall Field Conference, September 2021, Geology of Mount Taylor, Frey, Bonnie A.; Kelley, Shari A.; Zeigler, Kate E.; McLemore, Virginia T.; Goff, Fraser; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, pp. 117-128. https://doi.org/10.56577/FFC-71.117

[see guidebook]