"Following several days of mild Strombolian explosions at Southern Crater in late November, activity returned to weak emission of white vapour and minor blue vapour. This low activity persisted until 23 December when emissions became more voluminous. The next day, rumbling and roaring sounds from the crater were heard, and weak ejections of incandescent lava fragments were observed at night. Explosions were heard over the next few days and the emission cloud became grey or brown as the ash content increased. Crater glow or weak incandescent lava fragment ejections were seen on a few more nights near the end of the month.

"Seismicity increased slightly in accord with the visible activity at Southern Crater. Main Crater remained quiet throughout December, releasing small volumes of white vapour at low rates. Water-tube tiltmeter measurements . . . showed a deflationary trend through December, with an accumulated tilt of ~1 µrad."

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 and R. Stewart, RVO.