Report on Rabaul (Papua New Guinea) — 23 January-29 January 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
23 January-29 January 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, 23 January-29 January 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 23-24 January variable emissions at Rabaul mostly consisted of white vapor plumes, although following explosions gray plumes rose 600 m above the crater. Some roaring and rumbling noises were noted. Five explosions were detected between 0656 and 0859 on 24 January; these explosions produced light gray ash plumes that rose as high as 1 km above sea level. After the explosion at 0656 white plumes also rose from the crater. All plumes drifted E and ESE. Several explosions were detected between 1630 on 24 January and 0232 on 25 January, although seismicity remained at a low level. White vapor plumes and occasional light gray ash plumes rose from the crater and drifted E and SE.
About five explosions occurred between 1947 on 26 January and 0414 on 27 January, producing plumes that drifted ESE. An explosion at 1000 on 27 January produced a dense, billowing, light gray ash plume that rose a few hundred meters above sea level and drifted ESE. Ash emissions continued until 1500, followed by white vapor emissions. Six explosions were detected overnight, possibly generating ash plumes that drifted E and ESE.
During the morning of 28 January white vapor plumes rose from the crater. At 1003 an explosion produced a dense, billowing, gray ash plume; ash emissions continued from the next hour and then turned to white vapor. Two explosions occurred at 1323 and 1816, generating ash plumes and sub-continuous emissions for one hour and 15-20 minutes, respectively. Plumes again drifted E and ESE. White plumes rose from the crater afterwards through 29 January, but an explosion at 1723 generated a dense, billowing ash plume followed by a short period of sub-continuous emissions.
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 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)