Report on Manam (Papua New Guinea) — July 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 7 (July 1985)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Explosions and seismicity increase, then decline
Please cite this report as:
Global Volcanism Program, 1985. Report on Manam (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198507-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Seismicity remained at somewhat elevated levels (seismic amplitudes about twice non-eruptive levels) during the first half of July as Southern crater continued to emit dark brown ash clouds. At mid-month activity re-intensified with stronger Southern crater ash emissions, resulting in ashfalls in coastal areas. Seismic amplitudes rose to about four times non-eruptive levels and daily earthquake totals peaked at about 2,500, up from about 1,700. A slight decline in activity was evident from about 20 July and seismicity returned to the level of early July. Throughout the month, Main crater released weak to moderate, pale grey, low-density ash and vapour clouds. No significant tilt changes were recorded in July."
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.