Report on Manam (Papua New Guinea) — August 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 8 (August 1981)
Managing Editor: Lindsay McClelland..
Manam (Papua New Guinea) Incandescent lava, glow, sounds
Please cite this report as:
Global Volcanism Program, 1981. Report on Manam (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 6:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198108-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Brown or grey ash emissions from Southern crater were seen less frequently in August than in July. Main crater usually released white vapours, but grey or brown ash emissions were more common in August than at other times in 1981. Sound effects from the volcano ranged from weak rumbling to loud deep booming. Static dull orange-red glow at both craters overnight on 31 July-1 August was occasionally disturbed by flashes of bright orange-yellow glow, and sprays of incandescent lava fragments from Southern crater were also seen occasionally. Glow and ejections of incandescent lava fragments from Southern crater were observed 14 July, and glow from Main crater was seen on the 25th.
"Detailed analysis of seismic records indicates that, contrary to reports for June and July (SEAN 06:6-7), seismicity began a slight but apparently steady intensification in early June. For most of August, average seismicity was probably twice as strong as in the first half of 1981. The character of seismicity, however, is unchanged, and consists of volcanic B-type or explosion earthquakes. Tilt observations were steady in August."
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.