Report on Piton de la Fournaise (France) — 25 April-1 May 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 April-1 May 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 April-1 May 2018. 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 21 April, and then significantly on 23 April. A seismic crisis which began at 2015 on 27 April was accompanied by rapid deformation, indicating magma migrating towards the surface. The onset of tremor at 2350 heralded the beginning of the eruption, though the first visual confirmation of the eruption was recorded by the webcams at 0015 on 28 April.
The eruption took place from fissures at Rivals Crater, and the SW flank of Dolomieu crater. During an overflight around 0830, scientists noted that four fissures had opened, one of which intersected the crater. Lava fountains less than 30 m high rose from the entire length of the fourth fissure, which was 300 m long and at a lower elevation that Rival Crater. Several small lava flows formed a larger flow which traveled 200-300 m S towards the Enclos Fouqué. Tremor steadily decreased throughout the day, and by the end of the day the lava flow had slowed in an area around 300 m away from the rampart. During 29-30 April tremor levels were relatively stable, with a few fluctuations related to morphological changes at the eruptive site such as cone building. During an overflight around 1020 on 30 April scientists observed three active vents (S of Rival Crater). The third vent, in a 5-m-high cone, was mostly closed over, though it continued to produced lava flows. The middle and most active cone was about 30-40 m long and 10-15 m high, and had a vent with a lava lake. Large bubbles of lava rose from the lake and exploded into lava fountains. Lava fountains from the northernmost vent rose no more than 15 m high. Lava flows had traveled 150 m and 1.2 km; the longer lava flow had reached the S rampart and traveled an additional 400 m E along it.
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.