Report on Soufriere Guadeloupe (France) — January 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 1 (January 1982)
Managing Editor: Lindsay McClelland.
Soufriere Guadeloupe (France) Temperatures and chemistry of thermal springs
Please cite this report as:
Global Volcanism Program, 1982. Report on Soufriere Guadeloupe (France). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 7:1. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198201-360060.
16.044°N, 61.664°W; summit elev. 1467 m
All times are local (unless otherwise noted)
Since January 1979, samples have been collected 2-3 times per month from six springs with water temperatures of 25-69°C, 0.5-3.5 km from the summit dome. Water temperatures and chemistry remained nearly constant at five of the six springs, as shown by the following maximum variations recorded at any one spring in the nearly 3 years of sampling: temperature (°C) 4%, pH 5%, Cl 20%, HCO3 25%, F 25%. These variations were independent of rainfall and apparently random.
However, Carbet l'Echelle spring, the hottest and nearest to the summit (0.5 km) showed appreciable changes during the survey period. Its water temperature dropped from 69°C in January 1979 to 57° in November 1981, while the concentration of HCO3 ions approximately doubled and large variations in Cl concentrations occurred (figure 9).
Geologic Background. La Soufrière de la Guadeloupe volcano occupies the southern end of Basse-Terre, the western half of the butterfly-shaped island of Guadeloupe. Construction of the Grand Découverte volcano about 0.2 million years ago (Ma) was followed by caldera formation after a plinian eruption about 0.1 Ma, and then by construction of the Carmichaël volcano within the caldera. Two episodes of edifice collapse and associated large debris avalanches formed the Carmichaël and Amic craters about 11,500 and 3100 years ago, respectively. The presently active La Soufrière volcano subsequently grew within the Amic crater. The summit consists of a flat-topped lava dome, and several other domes occur on the southern flanks. Most historical eruptions have originated from NW-SE-trending fissure systems that cut across the summit and upper flanks. A relatively minor phreatic eruption in 1976-77 caused severe economic disruption when Basse-Terre, the island's capital city, which lies immediately below the volcano, was evacuated.
Information Contacts: S. Bigot, Lab. de Géochemie, Paris; G. Hammouya, Lab. de Physique du Globe; J. Le Mouel and J. Cheminée, IPG, Paris.