A brief period of heightened emissions took place at South Crater in early April. Following several days of weak vapor emission only occasionally containing a little ash, on 6 April the crater continuously discharged thick gray ash clouds that rose to ~1 km above the summit. The emission was accompanied by roaring sounds heard at 5- to 10-minute intervals. At night incandescent lava fragments were ejected hundreds of meters above the summit. Similar activity persisted over the following two days although at a slightly reduced intensity.

South Crater emissions weakened significantly after 9 April and then waned through the remainder of the month. Crater glow was seen on most nights until 20 April. Emissions typically contained ash until 21 April. During the rest of the month the only emissions at South Crater consisted of gentle, weak to moderate, white vapors.

Main Crater produced only white vapor during the first five days of April and then began emitting weak to moderate amounts of ash on many days, particularly in the last week of April. Weak to very weak crater glow was seen on two nights (1 and 12 April).

As of 22 May, the seismic records for the first three weeks of April had not yet been analyzed. Seismicity in the last week of April was weak to moderate with ~300-800 low-frequency earthquakes/day. Seismic amplitudes were low. Measurements from the water-tube tiltmeters 4 km SW of the summit lacked any apparent trend.

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, H. Patia, D. Lolok, P. de Saint Ours, and C. McKee, RVO.