Report on Manam (Papua New Guinea) — August 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 8 (August 1987)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Maps of 30 June eruption products; low-level activity
Please cite this report as:
Global Volcanism Program, 1987. Report on Manam (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 12:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198708-251020.
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 prevailed through August. Southern Crater released only a thin white plume. Main Crater released white vapor at low rates, and displayed steady night glow from 18 August. A moderately low level of seismicity continued with 1,400-1,500 sub-continuous, small-amplitude, low-frequency events/day. No significant tilt change was recorded during the month. Figures 2 and 3 show the distribution of the products of the 30 June eruption. Pyroclastic flow volume was estimated at 5-10 x 106 m3. Estimated volume of airfall ash was 106 m3.
|Figure 2. Scoria distribution (hatched pattern) and thickness (cm), and ash distribution (stippled) and thickness (mm) from Manam's 30 June 1987 eruption. Ash fell after the scoria and overlies it. Courtesy of RVO.|
|Figure 3. Distribution of flow products of Manam's 30 June 1987 eruption. PF = pyroclastic flow, WS = welded scoria, 1 = lava flow. Courtesy of RVO.|
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, P. de Saint-Ours and P. Lowenstein, RVO.