Report on Rabaul (Papua New Guinea) — May 1995
Bulletin of the Global Volcanism Network, vol. 20, no. 5 (May 1995)
Managing Editor: Edward Venzke.
Rabaul (Papua New Guinea) Slow deflation and weak vapor emissions; earthquakes N of the caldera
Please cite this report as:
Global Volcanism Program, 1995. Report on Rabaul (Papua New Guinea). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 20:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199505-252140.
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
"There was no eruptive activity at Tavurvur in May. Since 16 April only weak white vapour emissions have been seen from Tavurvur's summit area. This trend of low activity was confirmed by the seismicity in May. During the month only 16 low-frequency earthquakes were recorded. These earthquakes were not associated with activity at Tavurvur, and appear to originate immediately N of the caldera. Nineteen high-frequency earthquakes were recorded, compared to 6 in April. Eleven of these occurred on the 17th and were located outside the caldera, 1-3 km to the N. Most of the other located events occurred SSW of the caldera. Electronic tilt measurements from the station on Matupit Island continued to show a slow deflationary trend."
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.
Information Contacts: Ima Itikarai and Ben Talai, RVO.