Report on Manam (Papua New Guinea) — 29 December-4 January 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 December-4 January 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Manam (Papua New Guinea). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 December-4 January 2011. Smithsonian Institution and US Geological Survey.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
RVO reported that on 25 December a new episode of eruptive activity from Manam's South Crater began and was characterized during 25-29 December by rising ash plumes and ejections of incandescent lava fragments. Although most of the material fell back into the crater, some was deposited around the summit area, and some larger fragments were deposited in the SW and SE valleys. The Main Crater produced white plumes occasionally laden with ash. Incandescence was visible on some nights.
On 30 December activity from South Crater increased and was reported by observers in Bogia, 20 km SSW, on the mainland. A dense ash plume rose 3 km above the summit crater and drifted NW. An observer at Tabele on the SW flank confirmed the eruption and also reported that three pyroclastic flows descended the SE valley, stopping by a few to several hundred meters from the coastline. The first and largest pyroclastic flow devastated a broad unpopulated area between Warisi and Dugulava villages. Ash plumes drifted NW and caused light ashfall in Tabele. RVO recommended an increase in the Alert Level to Stage 3. Later that day, ash emissions and incandescent fragment ejections diminished.
On 31 December, gray ash plumes rose 200-300 m above the South Crater and also above the Main Crater. Low booming sounds were noted and incandescence from the crater was observed at night. During 1-4 January eruptive activity continued from South Crater and gray-to-black ash plumes rose above the summit crater. Incandescence emanated from the crater. During 3-4 January incandescent fragments were ejected onto the flanks and rolled down the SE valley. White vapor rose from the Main Crater.
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.
Source: Rabaul Volcano Observatory (RVO)