Report on Piton de la Fournaise (France) — 4 April-10 April 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 April-10 April 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 April-10 April 2007. 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 on 30 March at 2300, a 9-hour eruption from the SE flank of Piton de la Fournaise produced a small lava flow. On 2 April, a fissure that opened on the S-part of Grand Brûlé also produced a lava flow that reached the sea later that day. The flow velocity was estimated at 100 cubic meters per second, a value not seen at Réunion Island within the last 20 or 30 years. Lava fountaining to 100 m was observed at the point of emission during 4-6 April. On 6 April, very liquid and fast-moving lava reached a higher velocity than on 2 April in the main channel and a'a' flows covered a broad area. Explosions and fragmentation of rock were observed at the point were the lava flows met the sea. Fine-grained particles and Pele's Hair were observed 10-20 km away and millimeter-sized grains of basalt were found within 5 km. Intense seismic activity was observed beneath the summit.
Based on aerial photographs on 7 April, an area of 1000 x 700 m of Dolomieu crater collapsed to an estimated depth of 300 m on the N side and 10 m on the NW edge; the estimated collapse volume was 50 million cubic meters. On 7 and 8 April, seismicity and the intensity of lava fountaining decreased. On 10 April, tremor decreased in frequency and two lava flows were observed, one reaching the sea.
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.