The Rabaul Volcano Observatory reported that activity at Manam's two main summit craters remained low to mild during February-April 2004. No HIGP-MODIS thermal alerts were recorded at Manam over the year to 11 May 2004. While RVO noted that the summit was covered in cloud for most of February, when it was clear the craters were releasing white vapor at weak to moderate rates. They reported that February's single explosion occurred at the Southern Crater on the 14th; it was accompanied by a thick gray ash cloud and weak roaring noises. The ash cloud rose several hundred meters above the summit and drifted NW producing fine ashfall. There was no night-time glow observed during the month.

Mild eruptive activity occurred at the Southern Crater over the period 15 March-1 April, with emissions of brown ash on 17, 18, 27, and 28 March. The ash clouds rose ~ 100-300 m above the summit and drifted SE, depositing small amounts of ash in the villages of Boakure and Warisi. Vapor was also emitted from Main Crater. Small low-frequency earthquakes occurred over the report period, with a slight increase in the amplitude of volcanic earthquakes on 24 March. Overall the level of seismicity remained low. RVO continued to advise people to stay away from the four main valleys near the volcano.

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: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory, Papua New Guinea.