Manam's summit crater activity was more vigorous in early February than in January. On 3 February South Crater made rumbling sounds and issued moderately thick, dark gray ash clouds to 600 m altitude. Weak fluctuating night glow was seen and ash fell on the island's E side. The number and strength of explosions increased over the next few days. On the night of 7 February, incandescent lava fragments were thrown ~130 m above the summit.

On 8 February, Strombolian eruptions from South Crater produced ash columns to 2-4 km height; associated pyroclastic flows advanced into the SE and SW radial valleys. Night glow began to decline after that; the last ash emission from South Crater took place on 15 February. Weak glow was seen on the nights of 24, 26, and 27 February.

At Main Crater ash emissions resumed on 5 February. On the 9th an ash column rose to 4-5 km altitude. Similar ash columns were seen over the next few days, though only rising to ~2 km altitude. On the 10th and 11th the crater ejected pyroclasts and produced a weak fluctuating glow; over the next few days the eruptive intensity declined. During 9-12 February, ash fell on the E, SW, and W flanks.

Three times on 11 February (0436, 0703, and 1237 GMT), aviation meteorologists at the Darwin Volcanic Ash Advisory Center issued reports that Manam erupted to 7 km; the ash cloud was predicted to drift S-SE, or W. Satellite data revealed weather clouds in the area and analysts were unable to distinguish an ash plume.

By 14 February the eruption column only rose to ~500 m. During 15-21 February, Main Crater primarily issued weak vapor-and-ash emissions. Larger amounts of ash were noted in the column beginning on 22 February and continuing until the end of the month. Although no seismic measurements were made during February, on the SW flank (4 km from the summit at the Volcano Observatory) the volcano tilted slightly southward (0.5 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: B. Talai, H. Patia, D. Lolok, P. de Saint Ours, and C. McKee, RVO; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin, NT 0801, Australia.