Report on Piton de la Fournaise (France) — 1 April-7 April 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 April-7 April 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 April-7 April 2020. 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 a seismic crisis at Piton de la Fournaise was recorded during 0815-0851 on 2 April and was accompanied by rapid deformation (10-20 microradians). After a lull in activity for about three hours, volcanic tremor beginning at 1220 indicated the likely arrival of magma at the surface, though weather conditions prevented visual confirmation. During an overflight that day around 1500 observers confirmed a fissure eruption around 1,900 m elevation on the E flank about 1.7 km from the center of Dolomieu Crater, and just below the 10-16 February eruption site. Lava fountains rose no more than 30 m. By 0625 on 3 April lava flows had traveled as far as the top of Grandes Pentes, at 1,000 m elevation and 3.8 km from RN2 (the national road). By 1500 no significant deformation had been recorded and five volcano-tectonic earthquakes were located less than 2 km deep. The report noted that the weak seismicity and minor deformation indicated that the magma followed an existing pathway while propagating towards the surface.
The average lava-flow rate during 3-4 April was between 2 and 45 cubic meters per second with an average around 7-10 cubic meters per second. Lava flows continued to advance, reaching 800 m elevation. During 0400-0900 on 5 April the seismic network recorded 10 volcano-tectonic earthquakes (less than 2 km deep) prompting a request for an overflight and an inspection of the flow field. The distal end of the lava flow was located at 550 m elevation, about 2.7 km from RN2. The lava-flow rate had increased to between 3 and 63 cubic meters per second with an average around 24.2 cubic meters per second on 5 April and increased again to an estimate average of 30 cubic meters per second on 6 April. The longest flow had stopped advancing with activity focused on a new, more southern lava flow. By 1000 on 6 April the southern lava flow had descended to 360 m elevation, or about 2 km from RN2, as mapped during an overflight. Large quantities of Pele's hair were located in areas to the N, especially in La Plaine des Cafres. A sharp decrease in tremor intensity was recorded around 1330 on 6 April, signaling the end of the eruption.
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.