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Dynamics, scaling analysis, and hazard assessment of volcanic gas clouds at Kolumbo volcano (Santorini, Greece)

Matteo Cerminara1, Peter Baxter2, Augusto Neri1, Steve Sparks3, Orlando Vaselli4, Georges Vougioukalakis5

  • Affiliations: 1Section of Pisa, Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy; 2Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK; 3School of Earth Sciences, University of Bristol, Bristol, UK; 4Department of Earth Sciences, University of Florence, Florence, Italy; 5Department of Natural & Technological Hazards, Hellenic Survey of Geology and Mineral Exploration, Athens, Greece

  • Presentation type: Poster

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

  • Poster Board Number: 79

  • Programme No: 3.14.13

  • Theme 3 > Session 14

Abstract

The 1650 CE Kolumbo (Greece) submarine eruption resulted in the deaths of up to 40 people on Santorini (Thera) due to exposure to a cloud of noxious volcanic gases. No ash was reported in the cloud, so the gas release can be inferred to be unrelated to explosive eruption with ash emissions. Based on medical evidence, reversible and lethal thresholds are reviewed for CO2 and H2S being the two main threads for volcanic gas emissions at Kolumbo. Expert elicitation indicates significant uncertainty, with probabilities of similar future gas releases ranging in 15-60-90% (5th-50th-95th percentiles) and a 2-17-50% likelihood of the gas cloud reaching Thera. A 4D multiphase fluid dynamics model (ASHEE) is employed to simulate turbulent gas cloud propagation and dilution under scenarios with source and meteorological conditions informed by expert elicitation and ECMWF-ERA5 2005-2016 data. Analytical predictive relationships are then derived through a scaling analysis based on non-dimensional parameters like the Richardson number. Results indicate a 50% probability of the gas cloud reaching Thera, even with a relatively modest volumetric flow rate of 103 m3 s-1 and a wind speed half of the average. However, hazardous concentrations (above 200 ppm of H2S and 10 vol.% of CO2) along the Thera's NE coast occur only if source gas flux exceeds 104 m3 s-1. Probabilistic integration suggests a 16-17 % likelihood of hazardous conditions, aligning with elicitation-based estimates. These finding enhance understanding of gas cloud dispersion dynamics and volcanic gas hazards, contributing to risk mitigation strategies for affected regions.