"Dark tephra emissions from Southern crater continued throughout January, although periods of white vapour emission became more common from the 16th. Roaring, rumbling, booming, and thudding sounds were more pronounced in the first half of the month. Incandescent tephra ejections were seen on most nights, occurring at intervals of 1-3 minutes. Ashfalls were reported on the E coast of Manam 7-15, 21-22, and 29-30 January.

"Activity at Main crater was subdued, consisting of weak white and brown emissions. Seismicity declined from a peak between mid-December and early January, and by mid-January seismicity was back to normal levels. Tilts were stable during January following the inflationary phase of December 1981."

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: C. McKee, RVO.