Report on Manam (Papua New Guinea) — May 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 5 (May 1987)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Strombolian activity
Please cite this report as:
Global Volcanism Program, 1987. Report on Manam (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 12:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198705-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Eruptive activity was weak for the first part of May with both Southern and Main Craters emitting weak to moderate ash-laden vapor. No glow was observed. Southern Crater also emitted small amounts of blue vapor. Occasional roaring was heard at the observation post 4 km SW of the vent.
Beginning 12 May activity began to increase. Glow and rumbling from Southern Crater were reported almost every day through the end of the month. On 20 May incandescent fragments from Southern Crater were observed reaching ~50 m above the crater. Heights of incandescent ejecta increased steadily through the month. On 28, 30, and 31 May short periods of continuous Strombolian activity occurred. Ash output increased and ejections of dark brown ash clouds became more frequent. Lava fragments reached a maximum height of 240 m on the 30th. On 29 and 30 May glow from Main Crater was reported for the first time since April 1985.
Seismic amplitudes remained steady through the month at the same level that has been recorded since January. The tiltmeter . . . indicated a downward tilt to the NW with both components showing ~2 µrad of change.
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 and P. Lowenstein, RVO.