Temporal and Spatial distribution of scoria cones in the Paricutin-Tancítaro volcanic region, Mexico: A morpho-chronometric approach to monogenetic hazard evaluation

The Paricutin-Tancítaro region (PTR), located in the SW sector of the Michoacán-Guanajuato monogenetic field, in central Mexico, is characterized by a high spatial density of monogenetic scoria cones around Tancítaro, a stratovolcano active in the middle Pleistocene. The PTR area has been active for around one million years, and the latest eruption, beginning in 1943, formed the Paricutin volcano. We use the Average Erosion Index (AEI) to estimate the relative ages of 170 PTR scoria cones located within latitudes 19°N and 20°N and longitudes -102.0° E and -102.7° E. The AEI quantifies the erosional state of scoria cones from a morphological analysis of their level contours extracted from a high-resolution DEM (the 12-m TanDEM-X in this case). The analysis provides a metric for the undulations along the level contour curves at different altitudes, reflecting the width and amplitude of erosional rills and gullies on the cone’s surface. We compute a functional relationship between AEI and age by correlating 10 published radiometric ages with the measured AEIs of those cones. Then, using that function, we assign an age to each of the 170 cones, assuming that all the monogenetic volcanoes in the analysis have been exposed to similar erosive conditions. Finally, we tessellate the study area with a 0.1° x 0.1° grid and identify the number of events per grid module to compute the probability of at least one eruption occurring in the module in a specific time, using a Poisson process distribution obtained from the count of the number of events per 20 ky time intervals. Our results suggest that the dispersed volcanic activity in the PTR started to increase after the last eruption of Tancitaro (~237 ka), with a further activity increase during the Holocene, mainly concentrated on the NE sector of Tancítaro, where Paricutin is located. Holocene vents align to the NE, parallel to the Tepalcatepec-Tangancícuaro normal fault system. Furthermore, our results suggest a spatial coincidence between the regions with a higher probability of an eruption, based on the obtained eruption history, and the location of the recent seismic swarms in the PTR, the last two in 2020-2021, suggesting an increase in volcanic and seismic hazards in that area. To what extent? It is the subject of our forthcoming research.