Mild Strombolian eruptive activity began in Southern Crater on 9 March. Sub-continuous emissions with occasional forceful ejections of pale grey and brown tephra clouds were observed, sometimes accompanied by blue vapour emissions. Tephra emissions were small to moderate in volume and were accompanied by weak to strong roaring and booming sounds. Crater glow and sprays of incandescent lava fragments (up to 80 m above the crater rim) were observed on most nights in March. No significant changes were observed in the activity at Main Crater, which continued to release small quantities of white vapour.

Daily totals of volcanic earthquakes ranged from 1,070 to 1,270 between 1 and 8 March, then increased steadily to 1650/day by 31 March. Amplitudes had been increasing during February but showed no further increase in March. No changes in tilt were recorded during the month, but ~10 µrad of inflationary tilt have been measured since Manam's last vigorous eruption, in 1984. About 17 µrad of inflationary tilt have accumulated since 1978 when the period of deflation following the 1974 eruption ended.

Further Reference. Mori, J., McKee, C., Itikarai, I., Lowenstein, P., Talai, B., and Patia, H., 1987, Recent inflationary tilt at Manam volcano, Papua New Guinea, as recorded on a water-tube tiltmeter: JVGR, v. 33, p. 361-362.

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 and P. Lowenstein, RVO.