RVO reported that another phase of Strombolian activity at Manam’s Southern Crater began around 1700 on 4 May when RSAM values increased to 100-150. A sharp increase in values was detected at 0330 on 5 May, though the highest RSAM value (1,400) occurred between 0500 and 0600. RSAM dropped rapidly to 200 by around 0700, and then by 1400 RSAM values were around 50.

Strombolian activity on 5 May was characterized by loud roaring and rumbling, ejected incandescent material, and ash and scoria fall; some phases of very strong activity occurred during 0530-0600. A lava flow traveled down the SW valley and stopped at 600 m elevation. Minor amounts of ash fell in all parts of the island including Warisi (E), Dugulaba (S), and Boda and Baliab (NW). Though weather clouds prevented visual observations of Manam during 6-8 May, activity in general was very low; noises and crater incandescence were absent, and seismicity was lower than it had been for many weeks (RSAM <50). RVO recommended that the Alert Level be lowered to Stage 2.

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.

Source: Rabaul Volcano Observatory (RVO)