Report on Piton de la Fournaise (France) — 17 May-23 May 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 May-23 May 2017
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2017. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 17 May-23 May 2017. Smithsonian Institution and US Geological Survey.
Piton de la Fournaise
21.244°S, 55.708°E; summit elev. 2632 m
All times are local (unless otherwise noted)
OVPF reported that a seismic crisis at Piton de la Fournaise began at 1340 on 17 May and was accompanied by rapid deformation that suggested rising magma; volcanic tremor was recorded at 2010. The seismic and deformation activity was located in the NE part of l’Enclos Fouqué caldera. During an overflight at 1100 on 18 May scientists observed no surface activity at the base of the Nez Coupé de Sainte Rose rampart (on the N side of the volcano) nor outside of l'Enclos Fouqué caldera, and suggested that fractures opened but did not emit lava.
Seismicity increased at 0400 on 18 May. The number of shallow (<2 km depth) and deep (>2 km depth) volcano-tectonic earthquakes progressively decreased over the next three days: 40 shallow and 22 deep on 18 May, 18 shallow and 22 deep on 19 May, 7 shallow and 9 deep on 20 May, 8 shallow and 1 deep on 21 May. Carbon dioxide concentrations in soils measured at remote stations were high. During a field visit on 22 May scientists mapped the deformation associated with the 17 May event and measured displacements that did not exceed 35 cm. On 23 May OVPF reported that the 17-18 May activity resulted in two new zones of fumaroles that followed the trends seen in seismic and deformation data.
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.