Spatio-Temporal Relationships between Fumarolic Activity, Hydrothermal Fluid Circulation and Geophysical Signals at an Arc Volcano in Degassing Unrest: La Soufrière of Guadeloupe (French West Indies)
Giancarlo Tamburello,
Séverine Moune,
Patrick Allard,
Swetha Venugopal,
Vincent Robert,
Marina Rosas-Carbajal,
Sébastien Deroussi,
Gaëtan-Thierry Kitou,
Tristan Didier,
Jean-Christophe Komorowski,
François Beauducel,
Jean-Bernard De Chabalier,
Arnaud Le Marchand,
Anne Le Friant,
Magali Bonifacie,
Céline Dessert,
Roberto Moretti
Affiliations
Giancarlo Tamburello
Istituto Nazionale di Geofisica e Vulcanologia, sezione di Bologna, 40128 Bologna, Italy
Séverine Moune
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Patrick Allard
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Swetha Venugopal
Laboratoire Magmas Volcans-OPGC, Université Clermont Auvergne, 63170 Clermont Ferrand, France
Vincent Robert
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Marina Rosas-Carbajal
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Sébastien Deroussi
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Gaëtan-Thierry Kitou
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Tristan Didier
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Jean-Christophe Komorowski
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
François Beauducel
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Jean-Bernard De Chabalier
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Arnaud Le Marchand
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Anne Le Friant
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Magali Bonifacie
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Céline Dessert
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Roberto Moretti
Institut de Physique du Globe de Paris, Université de Paris, UMR7154 CNRS, 75005 Paris, France
Over the past two decades, La Soufrière volcano in Guadeloupe has displayed a growing degassing unrest whose actual source mechanism still remains unclear. Based on new measurements of the chemistry and mass flux of fumarolic gas emissions from the volcano, here we reveal spatio-temporal variations in the degassing features that closely relate to the 3D underground circulation of fumarolic fluids, as imaged by electrical resistivity tomography, and to geodetic-seismic signals recorded over the past two decades. Discrete monthly surveys of gas plumes from the various vents on La Soufrière lava dome, performed with portable MultiGAS analyzers, reveal important differences in the chemical proportions and fluxes of H2O, CO2, H2S, SO2 and H2, which depend on the vent location with respect to the underground circulation of fluids. In particular, the main central vents, though directly connected to the volcano conduit and preferentially surveyed in past decades, display much higher CO2/SO2 and H2S/SO2 ratios than peripheral gas emissions, reflecting greater SO2 scrubbing in the boiling hydrothermal water at 80−100 m depth. Gas fluxes demonstrate an increased bulk degassing of the volcano over the past 10 years, but also a recent spatial shift in fumarolic degassing intensity from the center of the lava dome towards its SE−NE sector and the Breislack fracture. Such a spatial shift is in agreement with both extensometric and seismic evidence of fault widening in this sector due to slow gravitational sliding of the southern dome sector. Our study thus provides an improved framework to monitor and interpret the evolution of gas emissions from La Soufrière in the future and to better forecast hazards from this dangerous andesitic volcano.
