The activity level in April appeared similar to that in March. Moderate to strong white, gray, and brown emissions were reported. Summit glow was seen occasionally and was especially bright on 1 April. Seismic recording was patchy in April; recordings were made on only 6 days, down from 16 days in March. Increased seismic activity on 12 and 15 March was followed by a period of stronger activity beginning 27 March that probably persisted through 1 or 2 April. Seismicity was at a low level on 6 April but had increased considerably by 16 April when ~60 events were recorded. Activity then subsided and from 23 to 26 April very few volcanic earthquakes were recorded.

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.

Information Contacts: C. McKee and P. Lowenstein, RVO.