Report on Manam (Papua New Guinea) — July 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 7 (July 1986)
Managing Editor: Lindsay McClelland..
Manam (Papua New Guinea) Increased ash production, rumbling
Please cite this report as:
Global Volcanism Program, 1986. Report on Manam (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 11:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198607-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Activity . . . remained at a low level in July, although there appeared to be an increase in ash production from Southern Crater. Daily emissions from Southern Crater consisted of grey low-density [ash] clouds and white and blue vapours. On most days, light ashfalls were reported on the downwind areas of the island. From the 2lst through the 27th, there were more forceful emissions of black, higher-density ash clouds. From the 26th to the 30th, rumbling sounds were heard at Tabele . . . , although after the 27th the ash production appeared to have decreased to levels similar to those of the first half of the month. Emissions from Main Crater were limited to weak, white vapours. Seismicity remained at inter-eruptive levels with daily totals of ~1,200 events. There were no significant tilt changes recorded."
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: J. Mori and C. McKee, RVO.