Report on Manam (Papua New Guinea) — June 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 6 (June 1983)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Seismicity stays high; emissions, noises lessen
Please cite this report as:
Global Volcanism Program, 1983. Report on Manam (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 8:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198306-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Despite continuing high levels of seismicity, audible and visible activity tended to be less intense in June. Both craters produced pale grey ash-laden emissions in moderate volumes, accompanied by rumbling and booming sounds at intervals of 3-25 minutes. Most of the sounds seemed to originate from Southern crater.
"Blue vapours were also emitted from both craters, but particularly from Southern crater, resulting in a haze of blue vapour on the downwind flank of the volcano. Probably as a result of strong winds, the emission column rarely rose higher than about 100 m above the summit. On several days the bluish emission plume stretched out for several tens of kilometers. Fallout of ash was common in coastal areas, but usually light.
"Daily totals of volcanic earthquakes rose from about 2,400 at the beginning of the month to about 2,900 at the month's end. The amplitudes of discrete volcanic earthquakes were about three times normal at the beginning of the month, but rose to about five times normal 11-24 June. By month's end amplitudes had returned to early June levels. Tiltmeter measurements showed no trends 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.