"During July, there was a brief increase in the level of activity from Southern Crater, while Main Crater activity continued to remain at a low level. Activity from Southern Crater was low from 1 to 4 July with gentle emissions of small volumes of white vapour. From 1430 on 5 July onwards, activity increased as weak deep-sounding explosions were heard at 5-10 minute intervals accompanying forceful emissions of grey-brown ash clouds. Incandescent lava fragments were seen being ejected from Southern Crater during the evening until the activity stopped at 2130. Ash emissions continued to occur until 7 July, and only one explosion was heard on 6 July. For the remainder of the month, activity at Southern Crater continued at the normal low level, with only white vapour emissions and blue vapour observed on 12 and 15 July.

"Throughout the month Main Crater continued to emit white vapour, weak to moderate in volume. A whitish-grey plume was seen on 31 July. No sounds were heard and no night glow was observed.

"Seismic activity remained at a low-moderate level throughout the month, with small fluctuations in the number and amplitude of low-frequency earthquakes. On average ~1,170 earthquakes/day were recorded, and there was a brief quiet period from 25 to 27 July when <500 earthquakes/day were recorded. There were no significant tilt changes in July.

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, R. Stewart, and C. McKee, RVO.