Report on Soufriere Guadeloupe (France) — October 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 10 (October 1981)
Managing Editor: Lindsay McClelland.
Soufriere Guadeloupe (France) Temperature, magnetic field stable
Please cite this report as:
Global Volcanism Program, 1981. Report on Soufriere Guadeloupe (France). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 6:10. Smithsonian Institution.
16.044°N, 61.664°W; summit elev. 1467 m
All times are local (unless otherwise noted)
IPG geophysicists have installed three telemetering magnetometers and established a network of 20 additional non-telemetering magnetometer stations on the flanks of Soufrière. Although significant changes in the magnetic field were recorded over periods of a few [months] during the phreatic and seismic activity of 1976-77, no variations of more than 1.5 nT were detected between August 1980 and March 1981.
IPG geophysicists also drilled two boreholes, to 77 m depth in the summit dome, and to 97 m depth immediately beside the dome. The temperature measurement at the bottom of dome borehole decreased steadily, from 97.5°C in April 1978 to 87°C in December 1980. . . . No significant temperature variation was recorded in the borehole near the dome, which remained at about 19°C through 1980. The temperature of a fumarole (Lacroix) about 80 m below the summit dropped from about 160°C in July 1978 to just over 100° by January 1979 and has remained between 96° and 98°C in 1981.
Further Reference. Zlotnicki, J., 1986, Magnetic measurements on La Soufrière volcano, Guadeloupe (Lesser Antilles), 1976-1984: A re-examination of the volcanomagnetic effects observed during the volcanic crisis of 1976-1977: JVGR, v. 30, p. 83-116.
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: J. Pozzi, J. Zlotnicki, G. Simon, J. Le Mouel and J. Cheminée, IPG, Paris.