Report on Piton de la Fournaise (France) — July 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 7 (July 1986)
Managing Editor: Lindsay McClelland.
Piton de la Fournaise (France) Small pit crater eruption follows seismicity
Please cite this report as:
Global Volcanism Program, 1986. Report on Piton de la Fournaise (France) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198607-233020.
Piton de la Fournaise
21.244°S, 55.708°E; summit elev. 2632 m
All times are local (unless otherwise noted)
"During June and July, seismic activity was semi-continuous. Shallow events, always located under the summit craters, were frequent (1-5/day). Some deep events (3-5 km) under the E part of the caldera were also noted but were less frequent. Since the end of May, some rare deeper events have been recorded, but were located less precisely.
"A small eruption occurred during the night of 13-14 July (between 1810 and 0010) after only two very shallow seismic events (at 1710, 500 m under the summit, M 1.1-1.5). A very minor amount of lava was emitted inside the 29 March pit crater. Small fountains produced 10-15,000 m3 of lava. Access to the lava is still prevented by continuous wall collapse of the 85-m-deep pit crater.
"Since the beginning of June, small tilt variations have been observed (maximum 24 µrads). The permanent tiltmeter network (Bory station on the summit and Chapelle in the caldera) recorded neither progressive nor irregular variations during the 10 previous days. After the eruption, seismic activity remained at a low level."
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 J-F. Delarue, OVPDLF; J-L. Le Mouel, J-.L. Cheminee, A. Hirn, P. Blum, and J. Zlotnicki, IPGP; J. Lenat, Centre des Recherches Volcanologiques and Observatoire de Physique du Globe de Clermont Ferrand.