Report on Piton de la Fournaise (France) — 4 February-10 February 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 February-10 February 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, 4 February-10 February 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)
OVPDLF reported that 180 earthquakes at Piton de la Fournaise were recorded from 0400 to 0900 on 4 February, including five events greater than M 2. A seismic crisis began at 0910, tremor was recorded at 1050, and an eruption began at 1100. Observers noted that a fissure had opened on the S flank, triggering an Alert Level 2-2 (ongoing eruption) and the restriction of access by the public to the summit area. The fissure was 500 m long, starting from an area located 100 m outside and to the W of Bory Crater. Activity was concentrated on the southernmost part of the fissure. Lava was ejected from the vent about 10 m high and rapidly flowed SSW towards the Rivals Crater, branched, and spread in an area S and SE of the crater. By the late afternoon the farthest-reaching branch had traveled past Cornu Crater. Tremor levels decreased through the day and were relatively low by 1800; on 6 February tremor levels were very low. Small cones had formed over the vents and produced low gas plumes. Inclement weather reduced visibility of the eruption site, although on 8 February observers noted that lava continued to flow from the vents, and another flow traveled further W. On 9 February a vent was weakly active with small explosions and small splashes of lava. Tremor remained stable and low on 10 February.
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.