Report on Rabaul (Papua New Guinea) — 7 January-13 January 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 January-13 January 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Rabaul (Papua New Guinea). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 January-13 January 2009. Smithsonian Institution and US Geological Survey.
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
RVO reported that during 3-14 January gray ash plumes from Rabaul caldera's Tavurvur cone rose several hundred meters above the crater to 1.7 km (5,600 ft) a.s.l. and drifted SW and SE. Explosions or forceful emissions sometimes ejected incandescent lava fragments that fell back into the crater and occasionally onto the slopes. Ashfall affected areas downwind; Air Niugini suspended all its flights to Tokua airport (about 20 km SE) during 5-9 January. According to a news article, a local shipping company offered to take passengers to a nearby airport in New Ireland Province, an area not affected by the ash plumes. Based on analysis of satellite imagery, the Darwin VAAC reported that during 11-12 January ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted SE, E, and NE.
RVO reported that on 11 January two small vents opened on the SW flank of Tavurvur (one-quarter of the way up the flank) and emitted strong fumaroles. During 11-13 January, the vents ejected ash. On 13 January, two explosions produced dull booms and sounds resembling falling rocks. Ash plumes rose 200-500 m above the vents and drifted SE. Later that day, diffuse white plumes were emitted. Air Niugini flights into Tokua airport remained suspended on 13 January.
Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.