"Bagana's summit crater dome continued growing through January, to fill 95% of the crater and bulge up to about 30 m above the crater rim. A thick, ash-laden plume was fed by numerous sources in the dome. A large solfataric area on the upper E flank of the volcano was also contributing vapours to the plume. An ash haze was observed stretching horizontally more than 100 km to the NE at about 2,000 m altitude. The steep flanks of the volcano were covered with thin ash deposits and a large number of blocks from avalanches of unstable parts of the dome.

"The long-established N lava flow was still active, and was broadening and thickening on the NW basal slopes at about 900 m altitude. Frequent avalanching was taking place from the [edges of the flow near its terminus]."

Geological Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: P. de Saint-Ours, RVO.