RVO received no reports about volcanic activity at Bagana during 31 July-16 August due to the lack of information coming from the Torokina area. Photos of summit activity taken during 17-19 showed ash emissions rising no higher than 1 km above the summit and drifting SE; a small explosion produced an ash plume during the morning of 19 August. Deposits from small pyroclastic flows were also evident in the photos; lava flows and the pyroclastic-flow deposits were also identified in satellite data. Two temporary seismic stations were installed near Bagana on 17 August at distances of 7 km WSW (Vakovi station) and 11 km SW (Kepox station). The Kepox station immediately began recording continuous, low-frequency background seismicity. The Alert Level remained at Stage 2 (on a four-level scale).

Geological Summary. Bagana volcano, in a remote portion of central Bougainville Island, is frequently active. 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 characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although occasional explosive activity produces pyroclastic flows. Lava flows with tongue-shaped lobes up to 50 m thick and prominent levees descend the flanks on all sides.

Source: Rabaul Volcano Observatory (RVO)