Report on Rabaul (Papua New Guinea) — 8 November-14 November 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 November-14 November 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Rabaul (Papua New Guinea). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 8 November-14 November 2006. 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 25 October-1 November, Rabaul emitted thick white vapor and sub-continuous gray ash clouds. Fine ashfall was reported from areas N and NW, including Rabaul town. On 28 October, a large explosion produced an ash cloud that reached an altitude of 2 km (6,600 ft) a.s.l. and drifted NW. Fine ashfall was reported from areas downwind and lava fragments fell onto the flanks. Only continuous, thick, white vapor clouds were emitted during 1-7 November. Two explosive events occurred on 2 November. Ash plumes from the first explosion reached altitudes of 1.5 km (4,900 ft) a.s.l. Plumes from both explosions drifted N. During 3-10 November, occasional small-to-moderate ash emissions produced plumes that drifted SE, away from populated areas. During 11-13 November, thick white vapor and occasional gray ash clouds drifted SE, S, W, NW, and N. Fine ashfall was reported downwind on 11 November.
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.
Source: Rabaul Volcano Observatory (RVO)