Report on Piton de la Fournaise (France) — 14 October-20 October 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 October-20 October 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, 14 October-20 October 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 on 12 October there was a strong increase in tremor intensity at Piton de la Fournaise, with values reaching or exceeding those detected during the first few hours of the beginning of the eruption (24 August). A strong increase in sulfur dioxide emissions was also detected by a ground-based DOAS (Differential Optical Absorption Spectrometer); values on 2 October were 205 tonnes per day (t/d) and values on 12 October were 1,990 t/d. A satellite-based sensor recorded 1,138 t/d during 13-14 October which was twice the amount measured on 24 August. The satellite-based lava-flow rate on 14 October was 12 m³/s (±4 m³/s), consistent with model data. Strain measurements showed deflation. Several small ephemeral vents across the lava field produced lava flows, and in many instances hornitos were present at these vents. A hornito SW of the cone ejected spatter during 13-14 October. Activity continued to increase on 17 October. The cone continued to grow; the base was 100 m in diameter and it was about 40 m high. Parts of the cone rim continued to collapse, and a notch in the rim allowed for periodic lava-lake overflows.
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.