Report on Rabaul (Papua New Guinea) — 30 July-5 August 2008
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 30 July-5 August 2008
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2008. Report on Rabaul (Papua New Guinea) (Sennert, S, ed.). Weekly Volcanic Activity Report, 30 July-5 August 2008. Smithsonian Institution and US Geological Survey.
Papua New Guinea
4.2459°S, 152.1937°E; summit elev. 688 m
All times are local (unless otherwise noted)
RVO reported that during 25 July-4 August, ash plumes from Rabaul caldera's Tavurvur cone rose to altitudes of 1.7-3.7 km (5,600-12,000 ft) a.s.l. and drifted W and NW. Ashfall was reported downwind in Rabaul town, Namanula Hill, Malaguna, and surrounding areas. Occasionally incandescence at the summit was observed and roaring noises were reported. During 31 July-4 August, incandescent lava fragments were ejected along with some of the more forceful ash emissions.
Based on observations of satellite imagery and reports from RVO, the Darwin VAAC reported that low-level plumes rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted NW during 5-6 August.
Geological Summary. 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 asymmetrical 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 1,400 years ago. An earlier caldera-forming eruption about 7,100 years ago is thought to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the N and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and W 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.