OVPF reported that, based on visual observations and satellite data, a lava flow at Piton de la Fournaise had traveled 2.8 km S and then SE, and was 500 m from the S wall of Enclos Fouqué by 18 September. It was 660 m wide at the widest part. Volcanic tremor was at a low level and relatively stable on 19 September, and then decreased on 20 September. During fieldwork on 21 September volcanologists observed three active lava fountains that were continuing to build the cone. The E wall was 30 m high, particularly vertical, and appeared unstable with numerous fractures. The lava flows were well-channeled and had advanced several hundred meters since 19 September, threatening an OVPF seismic station. Volcanic tremor levels fluctuated during 21-22 September. Deposits of Pele’s hair were noted in the Grand Coude area (8-10 km SW) on 22 September. During an overflight that same day volcanologists noted that the three lava fountains in the cone were visible, and lava tubes had formed near the uppermost part of the channel. Volcanic tremor had doubled in intensity on 23 September. Compared to the beginning of the eruption on 15 September the sulfur dioxide emissions had decreased by a factor of six; gas plumes were small and drifted S and W, but were confined to the Enclos Fouqué.

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)