New Mexico Geological Society Annual Spring Meeting — Abstracts

The state of New Mexico has experienced over 400 volcanic events over the past 5 m.y., ranging from small basalts to large plinian eruptions. The eruptive vents are grouped into volcanic fields roughly aligned with two zones of structural weakness which cross New Mexico: the Colorado Plateau Transition Zone (TZ), and the Rio Grande Rift (RGR). The most recent activity was the eruption of two relatively large (>4 km³) basalts at approximately the same time (ca. 1 ka): the Carrizozo and McCarty's basalt.

Seismic and geodetic evidence suggest that magmatic activity of New Mexico has not ceased. Leveling measurements indicate an inflation rate of approximately 1.8 mm/yr over the Socorro Magma Body (SMB, a sill at 19 km depth). This research assesses both the recent and potential volcanism of NM in light of the possibility for volcanic activity and a lack of information surrounding future volcanism and its effects here. While volcanic eruptions may not present an immediate threat to the population of New Mexico, they clearly pose a risk which should be clarified when planning long-term development in the state.

The largest volume of material was erupted between 1-2 Ma (Fig. 1). The majority of that came from the large (VEI = 6-7) rhyolitic eruptions which formed the Toledo and Valles calderas in the Jemes Mts. Most of the eruptions over the past 5 m.y. have been smaller (VEl = 3-4) and mainly basaltic (figure 2). Simple linear regression of age vs. frequency data seems to show that the eruption frequency is increasing over time (Fig. 3). There is an average eruption probability of 0.0002 per year over the next million years, equivalent to 200 eruptions. The potential activity includes lava, cinder cone, maar, dome, and plinian eruptions. All of these have the capacity for minor to severe impact on the state's economy, transportation, agriculture, and communications.