Report on Piton de la Fournaise (France) — 6 March-12 March 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
6 March-12 March 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 March-12 March 2019. 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)
During an overflight between 0700 and 0800 on 6 March tourists observed a new active fissure on the NW flank of Piton de la Fournaise’s Piton Madoré, 150 m upstream of the main vent. The fissure likely opened the day before during 0900 and 1900. The tourist report noted that a small cone had formed, and a lava flow was traveling N. In the morning of 7 March at least six new vents were visible, although weather conditions prevented OVPF volcanologists from confirming if they were along a new fissure. During fieldwork on 8 March volcanologists inspected the 5 March fissure and observed a small cone ejecting material up to 10 m above the rim. Lava from the W side flowed a few tens of meters, and a flow from the N side progressed E. The new vents that opened on 7 March were confirmed to be along an E-W trending fissure. The vents were active, each producing 50-m-high lava fountains. The report also noted that samples from the 5 March and 7 March vents had different compositions, though no other details were noted. Lava flows traveled to around 1,000 m elevation.
Satellite images showed sulfur dioxide plumes drifting 450-550 km E on 8 March. Lava flows rapidly progressed during 8-9 March; the lava emission rate was variable, ranging up to 25 cubic meters per second (based on satellite data), although since the new fissures opened the highest values (over 50 cubic meters per second) measured the past few days were approximately 10 times higher than the average values recorded during the 2017-2018 eruptions. By 0800 on 9 March the flow front was at an estimated elevation of 650-700 m. After a phase of intense surficial activity during 9-10 March, with lava fountains rising as high as 100 m, lava-flow emissions ceased around 0628 on 10 March and seismicity significantly decreased.
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.