Report on Manam (Papua New Guinea) — June 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 6 (June 1984)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Stombolian activity; debris avalanches
Please cite this report as:
Global Volcanism Program, 1984. Report on Manam (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 9:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198406-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Moderate Strombolian eruptive activity continued throughout June, with slightly more intense activity at the beginning and end of the month. The plume formed by emissions from both craters rose to a height of about 1-1.5 km above the summit.
"Southern crater ejections took place at a fairly steady rate of 1-2 per minute. Pale grey-brown clouds usually rose about 250 m, although from 3 to 7 June the average height of ejection clouds was 400 m. The ejections were rich in incandescent material. Much of the ejecta was channelled into the SW valley where it cascaded down the precipitous headwall of the valley in debris slides. Main crater activity was weaker, consisting of lightly ash-laden emissions that were released relatively gently. Fluctuating glow was seen on 4 June, indicating lava ejections within the deep funnel-shaped crater.
"Peaks in seismic amplitude (up to 10 times normal) occurred on 2 and 28 June. Daily earthquake totals averaged about 2,400, 3-13 June; for the remainder of the month the daily average was about 1,750. No significant tilt changes took place in June."
Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
Information Contacts: C. McKee, RVO.