A low level of activity continued during September. Glow from Main Crater, frequently observed during the latter half of August, was observed only a few times in September. Main and Southern Craters weakly emitted white vapour. During the first half of the month, the emissions from both craters also contained small amounts of gray ash. No noises were heard during the month.

During September, the water-tube tiltmeter appeared to show an increased rate of change, after remaining fairly steady during July and August. A few microradians of inflationary tilt accumulated during the month. Seismic amplitudes remained at low levels, similar to August.

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: J. Mori, C. McKee, and P. Lowenstein, RVO.