Report on Manam (Papua New Guinea) — July 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 7 (July 1989)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Weak gas emission; new fissures on summit lava flow
Please cite this report as:
Global Volcanism Program, 1989. Report on Manam (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 14:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198907-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"A low level of activity continued in July. Southern Crater gently released weak to moderate amounts of thick white [emissions] with occasional light grey and blue emissions. Weak deep rumbling sounds, occurring at intervals of 5-40 minutes, were commonly heard throughout the month. Main Crater was less active, releasing only small amounts of white vapours. Seismicity continued at low inter-eruptive levels, with 400-1,080 small discrete B-type events/day.
"An aerial inspection and ground deformation measurements were conducted between the 20th and 23rd. The interiors of the summit craters were totally obscured by the emissions. The only notable change was the presence of arcuate fissures in the 1987 lava flow at the summit's E platform. Ground deformation work involved EDM, dry tilt measurements, and re-installation of two dry tilt stations that were damaged in 1987. Results of these observations will appear in the next report."
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: I. Itikarai and C. McKee, RVO.