Evolving open-vent activity at Popocatépetl volcano (2019–2024): satellite insights into conduit permeability, the 2023 paroxysmal phase, and the transition in dome-forming behavior

Popocatépetl, Mexico’s most active volcano and one of the world’s strongest volcanic SO 2 emitters, poses a major hazard to more than 20 million people. This study presents a comprehensive space-based investigation of its activity from 2019 to 2024, integrating thermal IR, UV gas absorption, radar, and VNIR satellite imagery. We analyzed Volcanic Radiative Power (VRP), SO 2 flux, crater depth, and thermal anomalies to characterize recent eruptive behavior. TROPOMI data reveal three distinct degassing regimes, from ∼1,100 t/d in 2019 to ∼3,000 t/d after 2023, with a mean of ∼1,600 t/d, among the lowest since persistent activity began in 1994. VRP ranged between 0.01–1,000 MW, declining until mid-2022 and rising before the May–June 2023 explosive phase. Popocatépetl ceased producing its characteristic pancake-shaped lava domes after 2020, marking a transition from dome-building cycles to a new activity regime characterized by small-scale, short-lived extruded lava bodies, with almost no associated morphological change. Variations in the VRP/SO 2 ratio suggest changes in conduit permeability associated with long-term crater deepening, with elevated ratios preceding the 2023 explosions, consistent with reduced gas escape and overpressure buildup. Following the 2023 paroxysm, high degassing decoupled from thermal emissions, indicating renewed magma input and sustained open-vent degassing. Due to limited extrusion, excess degassing and thermal output, calculated as volumetric fluxes responsible for degassing (Q degas ) and radiation (Q rad ), point to shallow magma convection. These findings underscore the importance of multiparametric satellite observations to detect transitions in eruptive style, conduit permeability, and degassing dynamics at open-system volcanoes such as Popocatépetl. • First continuous SO 2 flux dataset at Popocatépetl using TROPOMI-5P • Activity change from dome-building cycles to short-lived, small-scale lava extrusion episodes in 2020 • VRP/SO 2 ratio indicates reduced conduit permeability before the 2023 explosive phase • Satellite data reveal decoupled thermal and gas fluxes after the paroxysms of 2023 • Evidence of shallow magma convection sustaining persistent degassing, with the magma column tip exposed at the crater floor.