Volcanic activity at Manam from January 2011 through May 2013 (BGVN 38:06) consisted of occasional ash plumes and several pyroclastic flows. Most explosions during that period were minor, with ash plumes rising only a few kilometers in altitude and drifting 200 km downwind. From June 2013 through September 2014 activity was mild to moderate with most emissions only rising a few kilometers. Periods of increased activity included high seismicity and pyroclastic flows. Audible explosions were frequently reported.

Activity during June-December 2013. During June, Main Crater primarily emitted white vapor, and night glow was noted on 2 and 17 June. Seismicity varied during the year; the highest seismicity of 2013 was recorded in June due to a pyroclastic flow.

Activity levels at Southern Crater intensified on 13 June when weak emissions of diffuse gray plumes were followed by two explosions at midnight which were heard in Bogia, 25-30 km SSW. Between 14 and 15 June diffuse emissions of gray-brown ash continued, rising 100 m above the crater. On 15 June residents on the W side of the island reported audible explosions and incandescent lava ejections were observed during the night.

On 17 June Southern Crater's activity once again increased, with occasional dark ash clouds rising from the crater. During the night RVO noted crater glow, Strombolian activity, and associated noises/shockwaves. Strombolian activity further increased on 18 June with plumes rising about 800 m and drifting NW. At 0635 a small pyroclastic flow in SE Valley traveled down to 400 m elevation, resulting in ash clouds that rose 900 m. At night, On 19 June dark-gray ash plumes rising 200 m above the crater were accompanied by occasional explosive booming noises and shock waves. Observers noted incandescent lava ejections at night before a decrease in activity on 20 June. On 22 June ash plumes rose to 2.4 km altitude and drifted 45 km NE and NW.

During 22-31 July both craters released white vapor; Southern Crater also emitted blue vapor over 25-26 July. Deep and low booming noises were heard on the island on most days since 24 July, however, on 30 July a loud explosion was heard in Bogia. Seismicity fluctuated but remained high.

During August the Main Crater only emitted white plumes, but Southern Crater produced light gray ash that rose ~100 m and drifted NW during 18-20, 22-23, and 25 August. Glow was visible from Southern Crater on 19, 21-26, and 27-28 August; incandescent lava fragments were ejected during 21-25 August.

Based on a pilot observation, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that on 19 August an ash plume from Manam rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted 65 km NW. On 26 August, ash plumes rose to 3 km altitude and drifted ~150 km NW. RVO noted dark emissions from that a small eruption that began at 1830 on 27 August, but that changed the next day to light gray-brown ash that rose 500-600 m above the crater and blew W to NW. Overnight until the morning of 28 August, there was crater glow, incandescent ejections, and associated noises. Afterwards, the activity subsided to minor emissions of diffuse gray-brown ash clouds.

During September, activity remained low except on 27 September when an ash plume rose from Southern Crater to 3 km altitude and drifted 45 km E. Both craters had low levels of activity from October to December; Main Crater emitted white vapor while Southern Crater emitted white and occasionally blue vapor. On 31 October, and 28 and 30 November, Southern Crater also generated light gray clouds and crater glow. Main Crater had occasional gray ash emissions during 13-14 December and crater glow was observed during 11-13 and 15 December. Southern Crater erupted gray ash on 6, 10, 13, and 14 December and had bright glow during 6-10 and 12-13 December. No plumes rose higher than 100 m above the crater.

Activity during January-September 2014. RVO reports for this period were only available for March and September 2014. During March the craters showed little to no activity and seismicity was low. Southern Crater had mild activity in September, except when an ash plume rose to 2.1 km altitude and drifted ~27 km NW on 6 September. Darwin VAAC observed the plume in satellite imagery from MTSAT (Multi-functional Transport SATellite) at 1032, though it was partially covered by meteorological clouds common in that area.

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: Rabaul Volcano Observatory (RVO), Department of Mineral Policy and Geohazards Management, Volcanological Observatory Geohazards Management Division, P.O. Box 386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC) (URL: http://www.bom.gov.au/info/vaac/).