"Main crater [experienced increased activity] for a few days in mid February. Ash-laden emissions from Southern crater also increased.

"White vapour was first observed over Main crater 8 February and increased on the 9th. This was accompanied by a change in the seismic pattern, with a progressive decrease in the daily number of B-type events (from 2100) but an increase in amplitude of the shocks.

"Activity stayed at low level until 15-16 February, when low to loud rumbling noises from Main crater were heard at 5-minute intervals. Harmonic tremor, formerly in bands, became continuous. Large amounts of blue vapour were observed with the white plume. On the night of 16 February red glow was seen over Main crater. The activity lasted 4 days and was accompanied by an increase in the daily number of recorded seismic events from 1400 to 1800.

"Beginning 20 February, night glow and blue vapour emissions disappeared, and rumbling noises and plume volume decreased. In the last days of the month seismic activity fluctuated between [1100] and 1300 daily events, but some explosions from Southern crater were again heard and recorded."

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: P. de Saint Ours and P. Lowenstein, RVO.