OVPF reported that a seismic crisis at Piton de la Fournaise was recorded during 0510-0554 on 4 December and was accompanied by minor, but rapid, deformation located just below the center and N rim of Dolomieu Crater. Seismicity declined after the crisis but inflation continued through 6 December. A second seismic crisis began at 0228 on 7 December and was again accompanied by rapid deformation. At about 0440 three fissures opened on the WSW flank of Dolomieu Crater at elevations between 2,300 and 2,190 m, spanning a 700-m-long area. Lava began erupting during 0455-0500. An overflight was conducted during 0700-0730; scientists observed lava fountains rising 15 m high from the three fissures and short lava flows. By 1700 the fissure at the highest elevation was the most active with five small vents while the other two fissures were noticeably less active. The eruption phase ended at 0715 on 8 December following a gradual drop in tremor and a three-hour phase of seismic signals indicating degassing. No surficial activity was visible.

Geological Summary. Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. 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 scarps formed at about 250,000, 65,000, and less than 5,000 years ago by progressive eastward slumping, leaving caldera-sized embayments open to the E and SE. Numerous pyroclastic cones are present on the floor of the scarps and their outer flanks. Most recorded eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest scarp, which is about 9 km wide and about 13 km from the western wall to the ocean on the E 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 outside the scarps.

Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)