Following the disastrous eruption of December 1996 (BGVN 21:12), Manam only showed mild activity throughout January. Seismic activity was generally low and monitoring was discontinued on 28 January. The water-tube tiltmeters at Tabele Observatory (4 km SW of the summit) have shown no changes since the slight drop following the December eruption.

South Crater released gentle pale ash clouds at irregular intervals. Weak rumbling and roaring sounds were heard on 9, 22, 26, and 28 January. South Crater gave off night glow on 22 January and weakly emitted incandescent material on 28 January.

On most days, emissions from the Main Crater consisted of gentle continuous white vapor. Some ash emission occurred on 12 and 22-23 January, accompanied by weak roaring and rumbling sounds, and incandescent projections at night. All combined, the resulting ash clouds were generally low, rising to ~2,500 m altitude and were blown to the SE side of the island where they resulted in light ashfall.

At least two aviation reports gave warnings to pilots (SIGMETs) about Manam's 11 February plumes. The reports indicated the plumes reached ~7 km altitude.

Geological Summary. 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: B. Talai, D. Lolok, P. de Saint-Ours, and C. McKee, RVO.