Report on Manam (Papua New Guinea) — May 2002
Bulletin of the Global Volcanism Network, vol. 27, no. 5 (May 2002)
Managing Editor: Richard Wunderman.
Manam (Papua New Guinea) Strombolian eruption on 20 May followed by lower-level activity
Please cite this report as:
Global Volcanism Program, 2002. Report on Manam (Papua New Guinea) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 27:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200205-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Mild eruptive activity began from South Crater on 13 January 2002. Weak gray-brown ash clouds were emitted and fine, light ashfall was reported. Weak, deep, roaring and rumbling noises accompanied occasional explosions and fluctuating incandescence (BGVN 27:03).
The Rabaul Volcano Observatory (RVO) reported that during March 2002 clouds obscured the view, but the vent produced weak-to-loud roaring and rumbling noises at intervals of 5-10 minutes on some days and about an hour on other days. The average interval was about 20-30 minutes. Explosions occurred on 15, 17, 21, 22 and 27 March. Explosions produced projections of dark brown ash clouds that were visible above the cloud cover. Fine ashfall was observed on the SE, and occasionally on the NW, parts of the island on many days of the month. Most ashfall occurred during 14-31 March, coinciding with the period of more numerous and vigorous explosions. Another notable observation was the sound of cascading boulders and rock fragments into the SE valley. These sounds were usually heard following explosions or loud roaring noises. Incandescence was observed on most nights of the month. During 1-13 March, generally steady incandescence varied between a dull and a bright, steady glow, and during 14-31 March the glow was marginally brighter. Occasionally (4, 17, and 31 March), projections of red incandescent lava fragments were observed. Main Crater continued to release only weak-to-moderate volumes of white vapor during periods of visibility. No instrumental (including seismicity) recording was done in March.
A moderate-sized Strombolian eruption occurred on 20 May. A pilot reported an ash plume at a maximum height of ~9 km on 20 May at 0500. At 0945 on the same day an eruption cloud was visible on satellite imagery extending SW. The Rabaul Volcano Observatory reported that a continuous eruption occurred until about 1400 on 20 May. After that, activity consisted of forceful ash emissions in moderate volumes. The decline in activity led to the reduction in Alert Level from 2 ("eruption expected within weeks to months") to 1 ("non-threatening, background level"). According to the Darwin VAAC, the ash cloud produced from the 20 May eruption was no longer visible on satellite imagery by 22 May at 1515. People were reminded to be cautious when near the valleys SE and SW of the volcano.
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: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin VAAC, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina Northern Territory 0811 Australia (URL: http://www.bom.gov.au/info/vaac/).