The summit area of Manam was obscured for almost half of the month of July. When weather was clear, emissions of weak white vapor were observed from Southern Crater. Main Crater released weak-to-moderate volumes of white vapor. Manam was generally quiet during August with only discrete small emissions of pale-gray ash clouds from Southern Crater on 2, 3, 21, and 25-31 August. Ash clouds rose 500 m above the summit and were blown NW of the volcano resulting in light ash falls. Ash emissions were not accompanied by any audible sounds and there were no night glows above the summit craters. When there were no ash emissions occurring, Southern and Main Craters released small volumes of white vapor.

Seismicity remained at a low level. Counts of low-frequency volcanic events remained generally unchanged from previous months with about 980-1,420 B-type events of very low amplitude being recorded daily. The water-filled tiltmeter at Tabele Observatory (4 km SW of the summit) showed about 1 µrad of inflation in July and was relatively steady throughout 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: Ben Talai, RVO.