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Challenges in forecasting phreatic eruption hazards during volcanic unrests: insights from La Fossa di Vulcano (Italy) and La Soufrière de Guadeloupe (Lesser Antilles, France)

Silvia Giansante 1,2, Tomaso Esposti Ongaro1, Marco Pistolesi1,3, Mattia de' Michieli Vitturi1, Raffaello Cioni2, Jean-Christophe Komorowski4

  • Affiliations:  1Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Pisa, Italy; 2Università degli Studi di Firenze, Firenze, Italy; 3Università degli Studi di Pisa, Pisa, Italy; 4Institut de Physique du Globe de Paris, Paris, France 

  • Presentation type: Poster

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

  • Poster Board Number: 78

  • Programme No: 3.14.12

  • Theme 3 > Session 14

Abstract

Volcanic systems with hydrothermal activity are prone to phreatic eruptions, sudden steam-driven explosions caused by pressurised, high-temperature fluids released with the fracturing of overlying rocks. While usually smaller in scale than magmatic eruptions, phreatic events can be deadly, particularly in densely populated or tourist-frequented sites. Notable examples include the 2014 Mt. Ontake eruption (Japan), the 2019 Whakaari/White Island eruption (New Zealand), and the 2018 Kusatsu-Shirane explosions (Japan). Developing accurate phreatic eruption scenarios is critical for hazard assessment and risk mitigation, requiring numerical simulation to identify potentially affected areas and to quantify impacts. However, a key challenge lies in determining the parameters that govern such scenarios, including vent position and geometry, eruption energy, grain size, and erupted volume. These parameters significantly influence eruption dynamics and material dispersal but are often associated with high uncertainty. Geological and geophysical data provide essential insights into past events and ongoing unrests, aiding in the characterisation of eruption parameters. This study examines the challenges of eruption scenario definition through two case studies: La Fossa di Vulcano (Aeolian Islands, Italy) and La Soufrière de Guadeloupe (Lesser Antilles, France), both of which have recently entered states of unrest. We highlight how parameters uncertainty affects the modelling of eruption scenarios and emphasize the need for integrated geological, geophysical, and geochemical analysis to refine hazard models, ultimately improving risk mitigation in vulnerable volcanic regions.