Activity at both Southern and Main craters dropped to a low level in January following moderate activity during November-December 1997 (BGVN 22:11 and 22:12). Emissions from both craters consisted of weak to moderate white vapor. Southern Crater produced low roaring noises on 15 January and steady weak glow most nights during 8-31 January.

Seismicity showed no significant change with 1,000-1,400 low-frequency, low-amplitude earthquakes per day. Measurements from the Tabele water-tube tiltmeter showed a 1 µrad deflation.

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: Ben Talai, RVO.