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Hydrothermal Weakening and Slope Instability at La Fossa Cone, Vulcano Island (Italy): A Combined Approach Using Drone Imaging and In-Situ Strength Testing

Benjamin F. De Jarnatt1,2, Thomas R. Walter1,2, Michael. J. Heap3,4, Daniel Mueller1, Julia Nikutta5, Antonino F. Pisciotta6

  • Affiliations: 1GFZ German Research Centre for Geosciences, Potsdam, Germany; 2Institute of Geosciences, University of Potsdam, Potsdam, Germany; 3Université de Strasbourg, CNRS, Institut Terre et Environnement de Strasbourg, Strasbourg; 4Institut Universitaire de France (IUF), Paris, France; 5Institute for Geophysics, University of Muenster, Muenster, Germany; 6Istituto Nazionale di Geofisica e Vulcanologia (INGV), Palermo, Italy

  • Presentation type: Talk

  • Presentation time: Thursday 11:15 - 11:30, Room R290

  • Programme No: 3.8.4

  • Theme 3 > Session 8

Abstract

Volcanic flank instability poses several significant risks, including caldera collapses, landslides, rock avalanches, and tsunamis, establishing volcanic edifice weakening as a multi-hazard threat. Among various triggering mechanisms, hydrothermal alteration is a well-established factor that degrades the physical and mechanical properties of volcanic rocks, facilitating destabilization processes. While previous studies have examined the physicochemical impacts of hydrothermal alteration, they were conducted in laboratory settings, leaving broader geophysical patterns and regional variability less explored. For this study, we chose La Fossa Cone (Vulcano Island, Italy), the southernmost part of the Aeolian volcanic archipelago, as our field site. With a history of hydrothermal alteration, episodic periods of unrest, and recent episodes of mass wasting, La Fossa Cone serves as an ideal natural laboratory. Here, we utilized a combined approach of high-resolution drone photogrammetry, image analysis and classification, and in-situ rock strength measurements to investigate the spatial distribution and intensity of hydrothermal alteration and its effects on rock strength. Our results revealed (1) a heterogeneous distribution of alteration intensities, (2) a strong correlation between increased alteration and decreased rock strength, (3) the identification of the weakest rocks on altered flanks, and (4) a spatial association between zones of hydrothermal alteration and areas of active erosion or landslides. This integrated approach enhances our understanding of the connections between hydrothermal alteration, rock strength, and volcanic flank instability, providing a novel framework for hazard assessment and mitigation strategies in volcanic environments.