Report on Piton de la Fournaise (France) — November 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 11 (November 1985)
Managing Editor: Lindsay McClelland.
Piton de la Fournaise (France) Earthquake swarm then fissure eruption
Please cite this report as:
Global Volcanism Program, 1985. Report on Piton de la Fournaise (France) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:11. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198511-233020
Piton de la Fournaise
21.244°S, 55.708°E; summit elev. 2632 m
All times are local (unless otherwise noted)
"Seismic activity was very low during all of November and was at shallow depth (1-2 km) under the summit. Small deformation was measured only on the summit stations. Continuously-recording tiltmeters indicated progressive deformation on Bory Crater since 28 November.
"During the night of 1-2 December, a very short seismic crisis occurred. For 17 minutes, very shallow low-magnitude events occurred under Dolomieu crater at depths of 0.5-1.5 km. A 1.5-km fissure opened from the top of Bory crater down to the S flank of the central cone. This eruption lasted only 28 hours, from 2 December at 0215 to 3 December at 0600. The amount of basaltic lava emitted was very small.
"A major inflation pattern was recorded only on the summit stations. No deformation was found in the rest of the geodimeter net."
Geological Summary. Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. 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 scarps formed at about 250,000, 65,000, and less than 5,000 years ago by progressive eastward slumping, leaving caldera-sized embayments open to the E and SE. Numerous pyroclastic cones are present on the floor of the scarps and their outer flanks. Most recorded eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest scarp, which is about 9 km wide and about 13 km from the western wall to the ocean on the E 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 outside the scarps.
Information Contacts: H. Delorme and J. Delarue, OVPDLF; P. Bachelery, Univ. de la Réunion.