Report on Rabaul (Papua New Guinea) — 20 November-26 November 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
20 November-26 November 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Rabaul (Papua New Guinea). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 20 November-26 November 2002. 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)
Very heavy ash emission was observed at Rabaul caldera's Tavurvur cone on 24 November. A low-level plume was produced and no ash was visible on satellite imagery. RVO advised on 25 November that ash emissions were continuing from Rabaul, but at a reduced rate in comparison to previous weeks. Observations revealed that the ash content in the emissions was generally decreasing, and erupted ash clouds remained below ~1.5 km a.s.l.
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.