Report on Manam (Papua New Guinea) — August 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 8 (August 1989)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Minor ash emission; summit deformation
Please cite this report as:
Global Volcanism Program, 1989. Report on Manam (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 14:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198908-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Activity continued at a low level in August. Emissions from Southern Crater were mostly gentle, weak to moderate, white vapours with occasional grey and brown ash clouds that drifted NW of the island. A light ashfall was recorded on the W side of the island on the 30th. Low rumbling noises were heard on the 17th and 25th. Main Crater was less active, releasing weak amounts of white vapour. Seismic activity was steady at a low inter-eruptive level, with an average of 1,000 small B-type events/day.
"EDM data obtained at Manam in July is not interpretable in terms of simple inflation/deflation events at the summit. The data indicate a NNW shift of the summit area. Compared with the previous data set (November 1987), changes of +27 and -17 ppm were measured along lines on the S and N flanks of the volcano, while a change of +5 ppm was registered on the SW flank. Tilt data from Tabele Observatory . . . during the same time interval show no significant changes."
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.