Report on Manam (Papua New Guinea) — August 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 8 (August 1985)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Activity declines; ash emission; weaker seismicity
Please cite this report as:
Global Volcanism Program, 1985. Report on Manam (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 10:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198508-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"A decline in activity was evident in August. Although brown ash clouds were normally emitted from Southern crater, on several days only white vapours were released. Emissions from Main crater were usually white. Seismic amplitudes declined somewhat, but were still slightly above non-eruptive levels at the end of August. Daily earthquake totals were usually about 1,600, but rose briefly to about 2,400 between 24 and 26 August. Tilt measurements fluctuated over a 2 µrad range, with no clear trends."
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.