Low-level activity persisted in August. Both summit craters usually released white vapor in small amounts. Blue vapor was emitted from South Crater on a few days at the end of the month. Small, discrete explosions took place at South Crater on the 9th (1 event) and 13th (2 events).

During August seismic activity was low. Daily totals of low frequency earthquakes had a range of 200 to 1,280. Periods of tremor were recorded between the 6th and 11th. There was no visible activity associated with the tremor. Seismic amplitudes increased in the week before the seismograph became unoperational on the 27th. The water-tube tiltmeters (4.5 km SW of the summit) did not show any significant changes.

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 and B. Talai RVO.