Report on Manam (Papua New Guinea) — June 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 6 (June 1985)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Ash emission and seismicity
Please cite this report as:
Global Volcanism Program, 1985. Report on Manam (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198506-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Following the brief period of intensified activity 12-24 April, activity was mild at both summit craters until late June. Activity during this 2-month interval was characterized by gentle release of white or pale grey emissions with low ash content. No summit incandescence was observed, no tilt changes were recorded, and seismicity was weak.
"Seismicity began to increase in mid-June and seismic amplitudes reached a peak about 4 times non-eruptive levels on the 26th, then appeared to decline at the end of the month. The increase was apparently associated with Southern crater activity; its emissions became more voluminous from the 26th and consisted of dark brown ash. Fine ashfall was reported 4-5 km downwind 2 days later. Activity at Main crater did not appear to be affected and continued to consist of weak to moderate, pale grey, low-density ash and vapour clouds."
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.