Report on Piton de la Fournaise (France) — December 2004
Bulletin of the Global Volcanism Network, vol. 29, no. 12 (December 2004)
Managing Editor: Richard Wunderman.
Piton de la Fournaise (France) August-October eruption sends lava flows to the sea; pillow lavas
Please cite this report as:
Global Volcanism Program, 2004. Report on Piton de la Fournaise (France) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 29:12. Smithsonian Institution.
Piton de la Fournaise
21.244°S, 55.708°E; summit elev. 2632 m
All times are local (unless otherwise noted)
Inflation over the last year and a half, monitored by permanent GPS stations, has not been interrupted by six eruptions over this period, the latest during 2-18 May 2004 (BGVN 29:05). Increased seismicity and ground deformation reported by the Observatoire Volcanologique du Piton de la Fournaise (OVPDLF) in late June 2004 continued through 9 August when the seismic network recorded 50-70 low-intensity earthquakes. The third eruption of 2004 started on 13 August. Increasing seismicity and fissure opening had occurred since early July 2004. At 0240 in the morning of 13 August, a 25-minute seismic crisis beneath the summit preceded the opening of an ~ 500-m-long E-W fissure within Dolomieu crater, with the fissure continuing on the E flank to an elevation of 1,900 m. The main activity was located at 2,150 m elevation. A significant lava flow ran down the "Grandes Pentes."
Ten days after the beginning of the eruption, ~ 750 m of National Road 2 was overrun, and on 25 August lava from an 8.5-km-long system of lava tubes entered the sea. A 670-m-long, 320-m-wide platform was build up within several days, representing more than 2 x 106 m3 of material. A second smaller platform was build up in the following days by nearby lava flows entering the sea. Two small hornitos, up to 8 m high, formed on the seaside edge of the first platform. The main eruption phase stopped on 2 September. However, significant phreatic activity continued on the new platform and was followed by two minor phases from the main vent on the E flank, the last one stopping at about 0300 on 4 October. Formation of pillow lava was recorded by professional divers for the first time at île de la Réunion, at a water depth of 50 m in front of the new platform.
The Toulouse Volcanic Ash Advisory Center reported noteworthy eruptive activity beginning on 4 September, following the end of the main eruption phase. Ash reportedly fell near the volcano's summit, and a lava flow entering the sea produced a steam and ash plume that rose ~ 2 km. Emissions ceased on the morning of 7 September.
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.
Information Contacts: Thomas Staudacher, Observatoire Volcanologique du Piton de la Fournaise Institut de Physique du Globe de Paris, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr/ovpf/observatoire-volcanologique-piton-de-fournaise); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue G. Coriolis, 31057 Toulouse Cedex, France (URL: http://www.meteo.fr/vaac/).