Report on Manam (Papua New Guinea) — October 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 10 (October 1999)
Managing Editor: Richard Wunderman.
Manam (Papua New Guinea) Inflationary trend continues; seismic peak in mid-August
Please cite this report as:
Global Volcanism Program, 1999. Report on Manam (Papua New Guinea) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:10. Smithsonian Institution.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Throughout August-October, both Main and Southern Crater emitted varying amounts of white vapor. No noise or night glow was reported in either month. Prior to 13 August, a gray component to the plume was occasionally observed at Main Crater. The summit area was clear during 1-21 September, but was cloud-covered through the end of the month and sporadically during October.
Daily seismicity was at its lowest level in late July, but seismic amplitudes built up slightly until mid-August. Activity decreased subsequently, except one individual peak on 13 August with the highest daily energy level since November 1998. Seismic activity was stable at a low level in September and October.
The seismic peak on 13 August may have been related to an upward tilt toward the summit that built up until 10 August, at which stage it reached a level that has commonly led to increased eruptive activity. However, no significant activity occurred and a gradual down-tilting took place throughout the remainder of August. In September the water-tube tiltmeter 4 km SW of the summit registered ~5 µrad of inflation. The overall inflationary trend continued, with a total of ~20 µrad of inflation recorded between July and the end of October.
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 basaltic-andesitic stratovolcano to its lower flanks. These 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 observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent 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, Kila Mulina, and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.