Report on Piton de la Fournaise (France) — May 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 5 (May 1987)
Managing Editor: Lindsay McClelland.
Piton de la Fournaise (France) Seismicity, tilt, and summit intrusion
Please cite this report as:
Global Volcanism Program, 1987. Report on Piton de la Fournaise (France) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198705-233020.
Piton de la Fournaise
21.244°S, 55.708°E; summit elev. 2632 m
All times are local (unless otherwise noted)
Low but constant seismicity was recorded from mid-April to early May, particularly in the N part of the volcano (12 April) and near the summit. Later in May, seismicity increased, and events remained shallow, below the two summit craters. Rare, deeper events were recorded in the E summit area. Progressive inflation had begun in April. Dry-tilt indicated an average inflation of 70 µrads around Bory Crater. Permanent inclinometers confirmed the dry-tilt data. Around 23 April inclinometers indicated that inflation had stabilized but a permanent magnetic station (6) showed a significant decrease, especially in the 7 x 11 km summit caldera. On 2 June at 1957 an intrusion occurred in the summit area accompanied by a seismic swarm lasting over 30 minutes. When seismicity ceased at 2030 no eruption had occurred.
Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.
Information Contacts: H. Delorme and B. Gillet, OVPDLF; P. Bachelery, Univ de la Réunion; A. Hirn, J-L. Le Mouel, J-L. Cheminee, P. Blum, and J. Zlotnicki, IPGP.