Report on Piton de la Fournaise (France) — 22 September-28 September 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 September-28 September 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Piton de la Fournaise (France). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 September-28 September 2010. 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)
Starting on 14 August and continuing through 10 September, OVPDLF recorded a slow but steady increase in the number and magnitude of earthquakes from Piton de la Fournaise. Inflation of the summit area began in late August. A report on 13 September noted localized deformation W of Dolomieu crater and a small number of landslides in the crater. On 20 September a significant increase in earthquakes was recorded, although the average magnitude was low. The earthquakes were located at the base of Piton de la Fournaise, W and S of Dolomieu crater. A seismic crisis on 24 September was characterized by several tens of earthquakes located beneath Dolomieu crater, and occurred in conjunction with 3 cm of inflation. The Alert level was raised to 1 ("Probable or Imminent 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.