Report on Piton de la Fournaise (France) — 13 May-19 May 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
13 May-19 May 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 13 May-19 May 2015. 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)
OVPDLF reported that during 4-16 May the number and magnitude of earthquakes at Piton de la Fournaise increased, and inflation was detected at the base of the summit cone. Gas emissions intensified; specifically hydrogen sulfide emissions increased on 5 May after a peak of sulfur dioxide values on 3 May. A seismic crisis was detected on 17 May. Between 1100 and 1230 the network detected 200 volcano-tectonic events, and then at 1250 a more intense seismic crisis began. Significant deformation at the crater rim was detected and a few minutes later, at 1345, an eruption started outside and SE of Dolomieu crater in the Castle crater area. Visual confirmation occurred 15 minutes later as clouds moved away. Volcanologists observed the area and noted lava fountains from three fissures, and two lava flows. A very large gas plume emitted during the first few hours of the eruption rose 3.6-4 km altitude and drifted NW. The fissure furthest W stopped issuing lava fountains before midnight. On 18 May only one fissure was active and the SSW-drifting gas plume was much smaller. Hydrogen sulfide emissions continued to be high, and carbon dioxide emissions increased. Lava fountains from a single vent along the second fissure, further E, rose 40-50 m. The lava flow had traveled 4 km, reaching an elevation of 1.1 km. Three field observations occurred on 19 May; scientists observed lava fountains 20-30 m high, and the advancing lava flow which had traveled 750 m in the previous day, reaching 1 km elevation.
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.