Report on Manam (Papua New Guinea) — October 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 10 (October 1987)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Increased seismicity and vapor emissions; night glow
Please cite this report as:
Global Volcanism Program, 1987. Report on Manam (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198710-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
There was a marked, though moderate increase in the level of activity at the beginning of the month. Seismic amplitudes began a progressive increase during the first week of October, when visible changes were first noticed. A weak fluctuating night glow at Southern Crater was accompanied by low rumbling and an increase in the rate of vapor emission (including blue vapour). Main Crater showed no significant change in the intensity of night glow but the amount of blue and white-gray vapor increased. Seismic amplitudes remained steady and elevated through the end of the month.
Radial tilt, which had shown a steady rise since August, showed a rapid deflation of ~3 µrad after 15 October. Deflation was continuing at the end of the month.
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: J. Mori, D. Lolok, and P. Lowenstein, RVO.