Report on Rabaul (Papua New Guinea) — 10 August-16 August 2011
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 10 August-16 August 2011
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2011. Report on Rabaul (Papua New Guinea) (Sennert, S, ed.). Weekly Volcanic Activity Report, 10 August-16 August 2011. 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 a decline in frequency of ash emission from Rabaul caldera's Tavurvur cone during 9-12 August, and no distinct explosions were detected. Ash-rich plumes rose 1 km above the crater and drifted NW, causing ashfall in Rabaul town (3-5 km NW) and in areas between Toliap (10 km NW) and Tavui. Seismicity was very low, consisting of sub-continuous volcanic tremor associated with the ash emissions and some small discrete low-frequency earthquakes. Ash emissions ceased on 12 August. During 13-15 August white vapor plumes rose from the crater.
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.
Source: Rabaul Volcano Observatory (RVO)