The Observatoire Volcanologique du Piton de la Fournaise (OVPF) reported that a magmatic intrusion occurred beneath Dolomieu Crater at Piton de la Fournaise on 1 January based on seismic and deformation data. Seismicity began to increase at 0447 and by 0600 the seismic network had recorded 304 volcanic-tectonic earthquakes at depths of 1.6-2.3 km. The majority of earthquakes were less than M 1. The increased seismicity was accompanied by rapid, minor deformation (up to 10 microradians) at the summit area that lasted less than an hour. The data suggested that an intrusion occurred during 0445-0550 beneath the SW edge of Dolomieu Crater at a depth of around 1 km. The Alert Level was raised to 1 (or an Orange Alert) and access to the volcano was restricted at 0600. Seismicity decreased following the intrusion and returned to a pre-intrusion rate of about 1-3 earthquakes per hour.

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)