OVPDLF reported that on 30 March at 2300, a 9-hour eruption from the SE flank of Piton de la Fournaise produced a small lava flow. On 2 April, a fissure that opened on the S-part of Grand Brûlé also produced a lava flow that reached the sea later that day. The flow velocity was estimated at 100 cubic meters per second, a value not seen at Réunion Island within the last 20 or 30 years. Lava fountaining to 100 m was observed at the point of emission during 4-6 April. On 6 April, very liquid and fast-moving lava reached a higher velocity than on 2 April in the main channel and a'a' flows covered a broad area. Explosions and fragmentation of rock were observed at the point were the lava flows met the sea. Fine-grained particles and Pele's Hair were observed 10-20 km away and millimeter-sized grains of basalt were found within 5 km. Intense seismic activity was observed beneath the summit.

Based on aerial photographs on 7 April, an area of 1000 x 700 m of Dolomieu crater collapsed to an estimated depth of 300 m on the N side and 10 m on the NW edge; the estimated collapse volume was 50 million cubic meters. On 7 and 8 April, seismicity and the intensity of lava fountaining decreased. On 10 April, tremor decreased in frequency and two lava flows were observed, one reaching the sea.

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.

Sources: Observatoire Volcanologique du Piton de la Fournaise (OVPF), Observatoire Volcanologique du Piton de la Fournaise (OVPF)