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Report on Piton de la Fournaise (France) — 5 July-11 July 2023

Piton de la Fournaise

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 5 July-11 July 2023
Managing Editor: Sally Sennert. Written by Zachary W. Hastings.

Please cite this report as:

Global Volcanism Program, 2023. Report on Piton de la Fournaise (France) (Hastings, Z W, and Sennert, S, eds.). Weekly Volcanic Activity Report, 5 July-11 July 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (5 July-11 July 2023)

Piton de la Fournaise


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

All times are local (unless otherwise noted)

OVPF reported that the eruption that began on 2 July at Piton de la Fournaise was ongoing during 5-11 July. Though there were multiple active fissures at the start of the eruption, as of 3 July only the SE flank fissure was active, located on the upper part of Grandes Pentes at approximately 1,720 m a.s.l. Volcano-tectonic earthquake events (VTs) fluctuated throughout the week but remained low relative to the onset of the eruption. The amplitude of the volcanic tremor dropped abruptly at 2105 on 4 July following a M 2.3 earthquake directly below Dolomieu Crater, and again on 7 July. Lava ejections continued to build a cone over the active vent throughout the week. During an overflight on 7 July, a team from OVPF-IPGP determined that the lava flow had reached 1.8 km from the road but had not advanced since 5 July. The flow front did not extend any further to the E, but by 7 July active flows were moving through a lava tube. During 10-11 July flows traveled through lava tubes and were active at elevations above 1,300 m. Although clouds often prevented measurements, satellite analysis showed that lava flow rates fluctuated between 1.5 and 24 cubic m/s. The total volume of lava effused since the beginning of the eruption was an estimated 5.5 million cubic m. Deflation of the whole edifice during 3-6 July ended by 8 July, and no significant deformation was observed the rest of the week.

Geological Summary. Piton de la Fournaise is a massive basaltic shield volcano on the French island of RĂ©union 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.

Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)