Report on Piton de la Fournaise (France) — 19 July-25 July 2017
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 July-25 July 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, 19 July-25 July 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 seismicity at Piton de la Fournaise increased on 10 July and was followed by a seismic crisis that began around 1250 on 13 July. Events were mainly located below the S edge of Dolomieu Crater, between 500 and 1,000 m a.s.l. Inflation was also detected, concurrent with increased seismicity. An eruption began at 0050 on 14 July in an area 750 m E of the Kala-Pélé peak, 850 m W of Château Fort, and 2.2 km NE of Piton de Bert. During a survey at 0930 scientists observed a fissure about 450 m long with seven lava fountains rising as high as 30 m. The fountain on the downhill end had built up a cone and produced two lava flows. A sulfur dioxide plume drifted E. On 15 July only three fountains were active. The intensity of the eruption fluctuated during 15-17 July, and by 17 July activity was concentrated at one eastern cone. During 18-19 July a few vents within the cone were active, ejecting lava no higher than 20 m above the cone’s rim. By 21 July several lava tubes had formed, and fractures within the tubes produced small lava flows. During an overflight on 22 July scientists noted that the lava flow was over 2.8 km long with a maximum width of 0.6 km; the front of the flow had not advanced in the past seven days. Three main vents were active within the main cone and a fourth was just sporadically active. The eruption continued at least through 25 July.
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.