"Eruptive activity strengthened in August and it appears that the level of lava has risen within the volcano. Glow was visible above both Main and Southern craters on most nights, and ejections of incandescent lava were observed on several nights. The lava ejections were stronger from Main crater, rising occasionally 200-300 m above the summit. Brown ash was emitted from Main crater on many days and grey ash emissions were seen rarely. Southern crater discharged brown or grey ash on only a few days. Otherwise both vents released white and blue vapours. Eruptive sounds included rumbling, roaring, booming, and sharp detonations. Seismic activity showed a slight intensification, but tilts were steady.

"An aerial inspection was made on 19 August. Main crater was a circular pit several hundred meters wide and contained a broad mound of black lava (fragments?). The surface of the mound was about 50-80 m below the crater rim. A central, circular vent was discharging blasts of red incandescent lava fragments at 1-10 second intervals. Southern crater was a deep, funnel-shaped structure with a pool of red incandescent lava at its base. Copious quantities of blue vapour were being released from both craters at the time of the inspection."

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.