Report on Manam (Papua New Guinea) — 22 February-28 February 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 February-28 February 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Manam (Papua New Guinea). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 February-28 February 2006. Smithsonian Institution and US Geological Survey.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
A large eruption began at Manam on 27 February around 1733 from the volcano's Southern Crater. According to the Darwin VAAC, satellite imagery showed an umbrella cloud above the volcano and a strong hot spot. The edges of the ash cloud were ice rich and the eruption height appeared to be about 19 km (~62,300 ft) a.s.l. based on a warm temperature anomaly in the middle of the cloud indicating a stratospheric intrusion.
RVO reported that the strong phase of the eruption declined on 28 February around 0030. During the height of the activity, incandescent lava fragments were thrown 700-800 m high; ejection heights later decreased to 200-300 m. A large amount of ash was deposited on the E part of the island and lava flowed down the SW valley. By 1 March, only gas was emitted from Southern Crater, no noises were heard, and weak incandescence was visible around the vent. Incandescent lava fragments were thrown 100-150 m above the vent and fell into the crater. Main Crater gently emitted occasional ash clouds, and then gas later in the day. Field inspections on 28 February confirmed that a lava flow traveled down the SW valley to about 600 m elevation, a pyroclastic flow traveled down the same valley to about 500 m elevation, and the maximum ash thickness was about 7-8 cm on the E part of the island. After mid-February the seismic station at the volcano was not operating and radio communication with the observer at Bogia ceased. The island is inhabited by about 300 people who returned to the island after evacuating following the 27 January 2005 eruption. The Alert Level at the volcano was at "Stage 2."
Geologic Background. 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 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche 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 historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical 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.