RVO reported that during 1-7 December both diffuse and dense ash plumes rose 500 m above Manam's Southern Crater and drifted NW. Ashfall was reported in areas downwind. Roaring and rumbling were heard, and became loud and frequent on 4 December. Ejected incandescent tephra was observed at night, and a small volume of lava effused from a SE valley vent that formed in August. Small volumes of lava also flowed from a vent, adjacent to the first vent, which opened in late November. White vapor plumes rose from Main Crater during the reporting period. Data from the electronic tiltmeter showed a long-term inflationary trend towards the E. RVO warned residents to stay away from the four main radial valleys, especially to the SE and SW, because products of the current activity are channeled into them.

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.

Source: Rabaul Volcano Observatory (RVO)