Report on Manam (Papua New Guinea) — August 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 8 (August 1997)
Managing Editor: Richard Wunderman.
Manam (Papua New Guinea) Low-level eruptive activity at Main and Southern craters
Please cite this report as:
Global Volcanism Program, 1997. Report on Manam (Papua New Guinea). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 22:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199708-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Low-level eruptive activity continued at Main and Southern craters during August. In the first week of the month Main Crater emitted occasional pale gray ash clouds accompanied by low rumbling sounds. On the 13th, occasional gentle emissions of pale gray ash clouds occurred once more. By 18 August emissions became forceful and darker, richer in ash content, and were accompanied by low roaring sounds. Activity started to decrease on 20 August and by the end of the month only gentle ash emissions were observed. A weak steady red glow was observed around the crater mouth on the 28th.
Southern Crater occasionally emitted gentle pale gray ash clouds with low ash contents in August. Low rumbling sounds occurred only on the 4th and 6th. Continuous weak steady red glow around the crater mouth was noted every night. Small sub-continuous projections of glowing lava fragments were observed at nights during 6-9 August. The emissions rose to ~2,000 m altitude then were blown NW, causing light ashfalls on settlements along the coast.
There was no seismic recording until 15 August. On the 19th four small B-type events were recorded. Seismicity suddenly increased on 21 August with 1,320 events recorded. Seismic activity on the following days remained at moderate levels with 1,000-1,360 events/day. The water-tube tiltmeter at the observatory did not show any significant tilt changes during the month.
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: Ben Talai, RVO.