A total of ~7 x 10⁶ m³ of aphyric basalt was extruded in the 30 November-1 January fissure eruption. Throughout January seismicity was low and limited to rare events under the summit area. Deformation was insignificant. Strong seismicity began again on 4 February, when two deep events occurred E of the central cone. A brief but intense seismic crisis followed on 7 February between 2032 and 2220. Three events of M 2 were registered. An eruption phase began at 2240, as lava flows emerged from three fissures that opened in the S part of Enclos Caldera, close to the recent vents (S of Chateau-Fort Crater) and in the same region as the 1972 vents.

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.

Information Contacts: H. Delorme, D. Vandamme, and P. Nerbusson, OVPDLF; P. Bachelery, Univ de la Réunion; J-L. Cheminee, J. Dubois, A. Hirn, J. LePine, J. Zlotnicki, and P. Blum, IPGP.