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Report on Piton de la Fournaise (France) — October 1985

Piton de la Fournaise

Scientific Event Alert Network Bulletin, vol. 10, no. 10 (October 1985)
Managing Editor: Lindsay McClelland.

Piton de la Fournaise (France) Deflation after lava production ends

Please cite this report as:

Global Volcanism Program, 1985. Report on Piton de la Fournaise (France) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198510-233020

Piton de la Fournaise


21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)

"The eruption ended during the second week of October. After major lava extrusion in September, lava flows were emitted at low rates through a tube at 1800 m altitude [but 1900 in 10:9]. The total volume of lava for the September episode is estimated to be 17-20 x 106 m3. Degassing was very important, and eruptive cones were covered with sulfur deposits.

"Since the beginning of the month, a major deflation was detected on the E coast. This may correspond to the end of the inflation that began on 10 July (10:07). In mid-October, at the end of the eruption, this deflation was recorded both at the summit station and in the caldera. After some sporadic tremors, seismic activity associated with this eruption ended on 16 October."

Geological Summary. The massive Piton de la Fournaise basaltic shield volcano on the French island of RĂ©union 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. Delarue, OVPDLF, Réunion; P. Bachelery, Univ. de la Réunion.