Report on Manam (Papua New Guinea) — March 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 3 (March 1985)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Increased tremor but little change in ash-poor plume
Please cite this report as:
Global Volcanism Program, 1985. Report on Manam (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 10:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198503-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Activity has remained stable at a low level since the 25 August 1984 eruption. However, seismicity began increasing on 5 March and tremor amplitude reached a peak about 10 times normal on the 20th before decaying sharply to about 2-3 times normal on the 23rd. No definite changes were evident in the low-density ash and vapour cloud emissions from the summit craters, but explosion sounds were heard from 19 March after a period of silence starting in late February. The tiltmeters at Tabele Observatory registered a 3 µrad radial inflation in March."
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.