Report on Bagana (Papua New Guinea) — September 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 9 (September 1989)
Managing Editor: Lindsay McClelland..
Bagana (Papua New Guinea) Frequent rockfalls from active lava flows
Please cite this report as:
Global Volcanism Program, 1989. Report on Bagana (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 14:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198909-255020.
Papua New Guinea
6.137°S, 155.196°E; summit elev. 1855 m
All times are local (unless otherwise noted)
"Activity continued at a moderate-strong level in September. Strong emission of thick white vapours continued from the summit area. The emissions were reportedly grey on a few days. Rumbling and explosion noises were heard occasionally at the observation post, ~8 km S of Bagana.
"Rockfalls from active lava flows were observed frequently in a broad area on Bagana's S flank. A visit to the seismic transmitter site (~2 km SW on the summit) by staff of Bougainville Island Copper Limited in late September revealed that rockfalls had occurred nearby.
"Seismic monitoring . . . resumed 28 September. Consistent with visual observations, the seismograms contain a large number of rockfall events, on the order of 100-120/day. A few A- and B-type events were also recorded daily."
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, RVO.