RVO reported that the increased activity at Manam noted during 17-18 June continued on 19 June, and then declined on 20 June. On 19 June diffuse dark gray ash plumes that rose 200 m above the summit crater were accompanied by deep, loud explosive and booming noises occurring at short intervals. Very loud explosions accompanied by shock waves were heard at much longer intervals. Observers noted ejected incandescent lava fragments at night.

Decreased activity that started on 20 June carried through 30 June, and was characterized by diffuse ash emissions at the beginning of the period changing to diffuse white vapor emissions towards the end. Diffuse gray emissions rose from Main Crater during 19-22 June; explosion and booming noises were reported during 19-20 June. Seismicity was low. Activity at Southern Crater and Main Crater was low during 1-14 July; both craters emitted white vapor.

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)