"The impressive Main Crater eruption which began 8 August continued until about 13 September. Eruption sound effects of weak to strong rumbling declined after 10 September, and ash emission which had been moderate to strong early in the month waned after the 11th. Crater glows and occasional sprays of incandescent tephra were observed on nights at the beginning of September but ceased after the 13th. Steady, weak to moderate ash emission continued, however, from 14 September. Occasional blue vapour emissions from the main crater were observed throughout the month. The S crater released pale grey emissions at a moderate rate for most of September, but intensified activity was evident from the 23rd when ash emission became stronger, more dense, and took on a grey-brown colour. Sound effects of low rumbling were associated with the stronger explosive activity. no crater incandescence was seen, however blue vapour emissions were common from 13 September. Ashfalls in coastal locations were generally light and were reported during 1-12, 18, and 27-30 September.

"Slight changes were registered by the tiltmeters at Tabele Observatory on the SW flank of the volcano. These indicated an uplift of less than 1 µrad to the NW from Tabele. Amplitudes of B-type volcanic shocks were fairly steady at about twice non-eruptive levels until 21 September, when the amplitudes dropped sharply. For the remainder of the month seismicity was at non-eruptive levels. These changes show poor correlation with observed activity."

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: P. Lowenstein, RVO.