Report on Bagana (Papua New Guinea) — July 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 7 (July 1989)
Managing Editor: Lindsay McClelland.
Bagana (Papua New Guinea) Lava production and vigorous SO2 emission
Please cite this report as:
Global Volcanism Program, 1989. Report on Bagana (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 14:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198907-255020.
Papua New Guinea
6.137°S, 155.196°E; summit elev. 1855 m
All times are local (unless otherwise noted)
Quoted material is from RVO, with additional information on SO2 flux supplied by S. Williams. "Moderate eruptive activity continued . . . throughout July. The summit crater released moderate to strong volumes of thick white and sometimes grey emissions. Intermittent low rumbling sounds with occasional mild explosions were heard at the observation post ~10 km S of Bagana. Occasional night glows from the summit were observed, and rockfalls continued on the active lava flow(s). The effusive activity was not clearly seen during the aerial inspection, although voluminous white emissions on the S flank . . . probably originated from a steaming lava flow."
During an SO2 monitoring flight on the 27th from 0830 to 0910, a strong convoluted white cloud emanated from Bagana's summit, rising only slightly before being blown ~25-30 km downwind. The plume contained no ash but varied in size and opacity. Four traverses yielded SO2 flux measurements of 4,870, 4,800, 1,930, and 2,390 t/d. The large measured variations corresponded well with visual estimates of variation in the plume size. Based on the duration of the observations and the relative times of the traverses, the estimated weighted average of the flux data was 3,230 t/d. The September 1983 data were similar (yielding a mean value of 3,100 t/d) but showed less variation (2,300, 3,000, 4,200, 2,800, 3,000 t/d) suggesting a more steady state of degassing at that time.
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: B. Talai and C. McKee, RVO; S. Williams, Louisiana State Univ.