OVPF reported that a seismic crisis at Piton de la Fournaise began at 0513 on 29 July and was accompanied by rapid deformation. Tremor beneath the N flank began to be recorded around 1200, indicating the likely start of the eruption, though inclement weather conditions prevented visual confirmation. OVPF visited the site and conducted helicopter overflights around 1630 and observed three active fissures, with a total length of 450 m, that crossed the July 2018 flows on the NW flank (600 m from the Formica Léo). The fissures produced 20-30-m-high lava fountains and ‘a’a lava flows that traveled no more than 500 m. After a gradual decline, volcanic tremor ceased at 0430 on 30 July signaling the end of the eruption.

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)