Report on Rabaul (Papua New Guinea) — 4 September-10 September 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 September-10 September 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Rabaul (Papua New Guinea). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 September-10 September 2013. 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 1-31 August low-level activity at Rabaul caldera's Tavurvur cone consisted of pale gray plumes with variable but mostly minor ash content. Intervals between emissions ranged from tens of seconds to hours. Ash plumes rose as high as 1 km and drifted NW, causing ashfall mainly in a narrow band between the E part of old Rabaul town (3-5 km NW) and Namanula Hill, and further downwind towards Nonga area. Malaguna No. 1 and other parts of Rabaul town were also affected. Most noises were associated with forceful emissions and were short in duration. Seismicity was high and dominated by ash-emission events.
Ash plume characteristics were similar during 1-5 September, although the interval time between emissions ranged from tens of seconds to tens of minutes. Plumes rose 50 m and were immediately blown NW by strong winds which re-suspended older ash deposits in widespread areas including Rabaul town. Residents of Rabaul town reported a chlorine odor; RVO noted that the odor, although uncommon, did not represent an increase in activity.
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)