 |
Volcanic Hazard Atlas of the Lesser Antilles: Guadeloupe.
Jean-Christophe Komorowski, Georges Boudon, Michel Semet, François Beauducel, Christian Anténor-Habazac, Sara Bazin, and Gilbert Hammmouya |
Abstract. The volcanic island of Basse-Terre, which is part of Guadeloupe, consists of 7 main eruptive fields each composed of several volcanic centres. Based on current data, the Grande Découverte-Soufrière volcanic complex is the only centre to have been active in the last 10,000 years. The last magmatic eruption, which occurred about 560 years ago, was a complex eruption that had many similarities with the ongoing Soufrière Hills eruption on Montserrat. It culminated in the formation of the current Soufrière dome. All historical hydrothermal activity and the six phreatic explosive eruptions of 1690, 1797-98, 1812, 1836-37, 1956 and 1976-77 AD have taken place from fractures and vents on this dome. La Soufrière of Guadeloupe is a well-monitored active volcano located within the Parc national de la Guadeloupe and just 5 km N of the town of Saint-Claude (population 10,000). In the last decade the volcano observatory has recorded a systematic progressive increase in shallow low-energy seismicity, a slow rise of temperatures of some acid-sulfate thermal springs closest to the dome, and, most noticeably, a significant increase in summit fumarolic activity associated with HCl-rich and H2S acid gas emanations. Permanent acid degassing from two summit high-pressure fumaroles has caused vegetation damage on the downwind flanks of the dome and required closure to the public of parts of the most active areas since 1999. No other anomalous geophysical signals have been recorded. Apart from the most likely phreatic eruptions, dome eruptions generating pyroclastic flows (7 in the last 15,000 years) and partial edifice-collapses generating debris avalanches and blasts (10 in the last 15,000 years) represent the major eruptive events most likely to occur in the future from the Soufrière dome area. Such events would directly threaten about 72,000 people and cause widespread destruction to most of southern Basse-Terre, and require a total evacuation. The region and nearby islands could also be affected by ash fall and tsunamis.
