Report on Bagana (Papua New Guinea) — June 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 6 (June 1987)
Managing Editor: Lindsay McClelland.
Bagana (Papua New Guinea) Lava flow remains active
Please cite this report as:
Global Volcanism Program, 1987. Report on Bagana (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 12:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198706-255020.
Papua New Guinea
6.137°S, 155.196°E; summit elev. 1855 m
All times are local (unless otherwise noted)
Activity continued at a steady moderate level throughout June. Strong white vapour emissions were occasionally tinged with brown or grey ash. Several aerial inspections and close-up ground observations suggested that most of the emitted ash was derived from debris avalanches from the summit area where a mound of lava filled the crater. Rock slides were common at the edges of the active lava flow on the N to NW flanks. Occasional incandescent ejections from the summit were reported by a schoolteacher living near the S base of the volcano. Glow from the summit was reported often, although volcanologists camped at the E base of the volcano on 17-18 June did not observe any summit incandescence.
An experiment with paint marks on the central part of the lava flow and adjacent marks on the levee banks indicated that the speed of the flow at ~1,200 m elevation was only 1-2 m/day. At this elevation the flow channel is ~20-30 m wide and possibly 10 m deep. These measurements indicate a flow rate of 200-600 m3/day or ~105 m3/year. The total volume of the flow since 1975 is ~106 m3.
Geologic Background. 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: C. McKee and P. Lowenstein, RVO.