Report on Rabaul (Papua New Guinea) — 24 December-30 December 2008
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 24 December-30 December 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, 24 December-30 December 2008. 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 20-26 December gray ash plumes from Rabaul caldera's Tavurvur cone rose to altitudes of 1.7-2.2 km (5,600-7,200 ft) a.s.l. and drifted SE and W. Ashfall was reported in areas downwind, including Kokopo Town (SE). Rumbling and roaring noises were reported on some days. Explosions or forceful emissions sometimes ejected incandescent lava fragments that fell back into the crater and occasionally onto the slopes.
Based on analysis of satellite imagery and pilot observations, the Darwin VAAC reported that on 30 December an ash plume rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted N and NW.
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.