An inventory of phreatomagmatic volcanoes in the Trans-Mexican Volcanic Belt

This research presents an extensive inventory of 103 small-volume monogenetic phreatomagmatic volcanoes (PVs) along the Trans-Mexican Volcanic Belt (TMVB), aiming to evaluate the influence of the external environmental parameters in phreatomagmatic volcanism. The formation of PVs (maar-diatremes, tuff rings, and tuff cones) is facilitated by the interaction of small volumes of magma and available water, conditions supported by frequent small-volume distributed volcanism and inter-montane lacustrine basins in the TMVB, a Plio-Quaternary continental volcanic arc with over 3000 monogenetic volcanic structures, of which only about 3% are PVs. The inventory was analyzed, dividing the structures into two groups based on their surface morphology: maar-diatremes and tuff rings (MD-TR, 81%), and tuff cones (TC, 19%). Morphometric correlations allow differentiation between these groups, although there is an overlap that could be caused by the presence of magmatic eruptive phases in some PVs. The type of aquifer host is the only environmental parameter with some discernible influence on the size of PVs.

Most of the PVs are clustered in three specific areas: Valle de Santiago, Serdán-Oriental, and Los Tuxtlas. The PV clusters highlight the combinations of environmental parameters under which phreatomagmatism is most successful in terms of frequency and size. Less frequent sets of parameters are reflected in the scattered PVs. The magmatic flux, presumably low, is considered the first-degree influence on the conditions for a phreatomagmatic eruption, provided that there is water availability. This availability is determined by the local climate as second-degree influence and by the local hydrogeological configuration as third-degree. The hydrogeological configuration parameters involve the aquifer host, permeability, spatial distribution and hydraulic gradient. If these conditions, enhanced by a humid climate, facilitate the development of an extensive aquifer in an area of small-volume volcanism, it is more likely that a PV cluster will form. This inventory serves as a foundation for future research on phreatomagmatic volcanism in the TMVB, emphasizing the need for multidisciplinary studies to fill the existing gaps in knowledge regarding internal parameters and the interaction between magmatic and environmental factors.