Eruptive activity at Manam has generally been low following a significant explosion in late February 2006 (BGVN 31:02). Between March and July 2006 the Rabaul Volcano Observatory (RVO) reported intermittent, milder, ash explosions (BGVN 31:06). Similar variable activity has continued into early May 2007, with plumes frequently identified on satellite imagery by the Darwin Volcanic Ash Advisory Centre (VAAC).

RVO received a report that four people were swept away by a mudflow in the early hours of 13 March following heavy rainfall on the northern part of the island. A 5th person was reportedly critically wounded and in a hospital.

Activity during August-December 2006. On 4 and 5 August, an ash plume was visible on satellite imagery extending 30 km NW. Ash plumes were emitted again during 14-15August. Over the next couple of days, the emissions became more diffuse and weak incandescence was observed at night. Based on pilot reports and satellite imagery, continuous emissions during 17-21 August eached altitudes of 3.7 km and drifted NW. Eruptive activity from Main Crater during 22-23 August consisted mainly of dark brown-to-gray ash plumes that rose 1-2 km above the summit and drifted W and NW. The Darwin VAAC reported that eruption plumes were visible on satellite imagery on 23 and 26 August, extending NW. Southern Crater continued to release only diffuse white vapor.

From the end of August to 5 September 2006, the Darwin VAAC reported that ash-and-steam plumes reached altitudes of 4.6 km and drifted W. Steam plumes with possible ash were visible on imagery below 3 km and drifted NE. RVO reported mild eruptive activity during 15-17 October that consisted of steam and ash plumes. White vapor plumes were visible from Southern Crater and intermittently from Main Crater. Main Crater produced gray ash plumes on 19 October. Weak incandescence was seen during 15-17 and 29 October.

During 1-13 November, white vapor plumes rose from Southern and Main craters. Incandescence was noted from both craters during 8-10 November and from Main Crater on 12 November. On 13 November a diffuse plume seen on satellite imagery drifted W. Steady incandescence was again observed from Main Crater during 8-10 December and bluish white vapor emissions during 6-9 December changed to a darker gray on 10 December. Weak glow continued from Main Crater during 14-18 December and a white vapor plume rose just above 2 km altitude. Based on satellite imagery, diffuse plumes drifted mainly W during 13-15 December. The daily number of volcanic earthquakes fluctuated between 700 and 1,000.

Activity during January-May 2007. RVO reported that mild eruptive activity and emissions of white vapor plumes from Main Crater were observed during 1-14 January. Brown-to-gray ash plumes accompanied emissions on 6 and 9-11 January; and nighttime incandescence was observed intermittently. White vapor clouds were occasionally released from Southern Crater. Seismic activity was at low to moderate levels; the daily number of low-frequency earthquakes fluctuated between 500 and 1,000.

Satellite imagery showed diffuse plumes drifting WSW on 15 February. Southern Crater emitted gray ash plumes during 15-19 February and white vapor plumes on 21 February. Continuous gray ash plumes from Main Crater rose to an altitude of 2.3 km and drifted SE during 19-21 February. The daily number of low-frequency earthquakes fluctuated between 400 and 500 during 22-24 February before the seismograph developed technical problems.

Mild eruptive activity continued during 22 February-10 March. Main Crater forcefully released variable gray ash clouds on 22 February that rose less than 1 km above the summit before being blown SE. Incandescence was also visible that day. Poor weather prevented observations for the remainder of the month. When the clouds cleared on 3 March, Main Crater was seen sending ash clouds less than 500 m high. Glow was visible during 2-5 and 9-10 March. Southern Crater released occasional diffuse gray ash clouds on 3-4 and 6 March, but only white vapor on 5 and 7-11 March.

Main Crater continued to release occasional low-level ash clouds through 6 April. Incandescence was visible during clear weather on the nights of 11-12 and 16-18 March. Southern Crater released diffuse white vapor on 11-12 and 15 March; however, diffuse ash clouds were reported on 16-20 March. Weak roaring noises were heard on 24 March, and on 7, 12, and 26 April. Low-level plumes were seen during 25-26 April, and a small plume was blowing W on 28 April. Weak incandescence was again visible from Main Crater on 2 and 4 May. Diffuse plumes were seen in satellite imagery on 6 and 23 May. Seismic activity was at a low level, with the daily number of volcanic earthquakes between 800 and 1,000 events.

Thermal satellite data. Thermal anomalies were not detected by Moderate Resolution Imaging Spectroradiometers (MODIS) for 9 months after events related to the 27-28 February 2006 explosion. Anomalies reappeared in December, with hot pixels detected on 5, 7, 9, 10, 12, and 14 December 2006. Another anomaly was recorded on 19 April 2007. Additional thermal anomalies were present on 16 and 23 May 2007. Most of the pixels were located near the summit, or slightly towards the NE. The May anomalies were the furthest down the NE Valley.

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: Herman Patia and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/).