Report on Piton de la Fournaise (France) — 19 August-25 August 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 August-25 August 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 19 August-25 August 2015. 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)
On 24 August OVPDLF reported continued deformation and an increase in seismicity at Piton de la Fournaise during the previous several days, and a significant increase in seismicity that morning. Sulfur dioxide gas emissions increased at 1600, and at 1711 the seismic and deformation network indicated a magmatic intrusion. Lava fountains were visible at 1850 from a fissure on the S flank of Dolomieu Crater, at about 2000 m elevation, near Rivals Crater. The fissure propagated towards the top of Rivals, and at around 2115 a fissure opened to the NW, below Bory Crater. The lava-flow rate was 30-60 cubic meters per second. By the next morning fountains at higher elevations ceased, and were only active from a 100-m-long section near Rivals Crater. The lava flow rate had significantly decreased to 10 cubic meters per second. Near the top of the active fissure a 140-m-high cone had formed.
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.