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Thermal Footprints of the Central Crater at Mt. Etna (Italy): Insights into Abrupt Changes in Surface Permeability, Hydrothermal Alteration, and Sporadic Thermal Anomalies

​Benjamin F. De Jarnatt1,2, Thomas R. Walter1,2, Valentin R.Troll3, Michael J. Heap4,5, Claire E. Harnett6,  Emanuela De Beni7, Valerian Schuster1, Harald Milsch1

  • Affiliations: 1GFZ, German Research Centre for Geosciences, Potsdam, Germany; 2University of Potsdam, Potsdam, Germany; 3Department of Earth Sciences, Natural Resources and Sustainable Development, University of Uppsala, Uppsala, Sweden; 4Université de Strasbourg, CNRS, Institut Terre et Environnement de Strasbourg, Strasbourg, France; 5Institut Universitaire de France (IUF), Paris, France, 6UCD School of Earth Sciences, University College Dublin, Dublin, Ireland; 7INGV, Istituto Nazione di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 31

  • Programme No: 3.8.15

  • Theme 3 > Session 8

Abstract

Volcanic outgassing and hydrothermal alteration are well-known processes in volcanic edifices, typically controlled "bottom-up" by fluid overpressure, density contrasts, and fractures or faults that serve as pathways for volcanic outgassing at the surface. At the rim of the Central Crater of Mt. Etna (Italy), our studies have revealed a previously unrecognized mechanism driving these processes "top-down," creating distributed fumarole depressions up to 6 m wide and 1 m deep. These depressions, characterized by thermal exhalation and hydrothermal activity, were mapped using high-resolution geospatial data obtained with a drone equipped with an infrared sensor and an RGB camera, identifying over 100 anomalies. We find that many of them host basaltic bomb fragments, thus resembling bomb impact sites. Rock samples collected from selected locations were then analyzed using mercury intrusion porosimetry to gain further insights into the porosity and permeability characteristics of the material at depth. These findings offer a new perspective on how volcanic bomb impacts can influence abrupt shifts in surface permeability, thereby affecting outgassing pathways and associated alteration. Our interpretation of the results suggests that volcanic bombs from the May 21, 2023, South East Crater paroxysm impacted the surface, breaching an otherwise sealed surface and puncturing a hydrothermally altered cap. These impacts enabled localized pathways for outgassing, producing distinct thermal and alteration anomalies that control the locations of fumaroles along the crater rim. Furthermore, we discuss how this "top-down" fumarole formation may play an essential role in understanding volcanic outgassing efficiency, mineralization, and the structural stability of volcanic systems.