Report on Piton de la Fournaise (France) — 23 October-29 October 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 October-29 October 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, 23 October-29 October 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)
OVPF reported that inflation began to be detected at Piton de la Fournaise on 11 October and a seismic crisis was recorded on 21 October. A second seismic crisis began at 0415 on 25 October accompanied by rapid deformation. Volcanic tremor began at 1440, signaling the arrival of magma to the surface; the eruption area was not visible in webcam views. Field observers first saw two active fissures at the S part of l’Enclos Fouqué at an elevation of 1,400 m. Several lava flows were identified, with the front of the longest flow reaching an area 2 km upstream from National Road RN2 by 1700. Tremor intensity began to decline around three hours after the start of the eruption and continued to decline through the morning of 26 October. That same morning there was one active vent producing 10-20-m-high lava fountains. Downstream of piton Tremblet the flow forked and by 1700 on 26 October the leading toe was about 250 m from RN2. On 27 October tremor intensity fluctuated concurrently with the variable intensity of cone formation. The cone had grown to 10 m high and lava was ejected 20 m above the cone rim. Only one lava flow was active and was 200 m long; the flow near RN2 had not progressed. The eruption ceased at 1630.
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.