Shallow magma ponding and degassing beneath Mt. Etna summit craters inferred from multi-parameter survey

Monitoring active volcanoes requires the integrated analysis of multidisciplinary datasets to constrain magma migration and its temporal evolution. Here we present a multidisciplinary study combining geochemical observations, seismic–volcanic signals, and thermal satellite data to investigate magmatic processes within Mt. Etna’s shallow plumbing system. The integrated dataset allows us to assess magma ponding, convection, and degassing dynamics, with particular emphasis on halogen gas emissions.

Halogen fluxes are used to evaluate the efficiency of magma residence and the steadiness of magma supply in the shallow system. From January to April 2023, persistent thermal anomalies, low infrasound activity, stable volcanic tremor, and sustained halogen degassing indicate a steady-state degassing regime and efficient magma rejuvenation at shallow levels. From late May 2023, an increase in SO₂ emissions not accompanied by a proportional increase in HCl emissions, together with enhanced infrasound activity, increased tremor amplitude, and sporadic thermal anomalies, suggests a decoupling between deep gas ascent and magma ascent within the main conduit.

These observations indicate that halogen flux monitoring, owing to the high solubility of halogens in silicate melts, provides a sensitive indicator of changes in magma supply rate and near-surface magma residence time in basaltic volcanic systems.