Report on Rabaul (Papua New Guinea) — 27 November-3 December 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
27 November-3 December 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, 27 November-3 December 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)
The eruption at Rabaul caldera's Tavurvur cone continued through 3 December. The intensity of ash emission changed on 30 November from very slow to slightly forceful, and the interval between eruptions increased. Occasional moderate eruptions produced ash clouds that reached heights of 1-1.5 km above the crater. Two moderate explosions on the night of the 30th emitted visible incandescent lava fragments that showered the volcano's N and NE slopes and ash plumes that rose several hundred meters above the crater. On the evening of 3 December ash plumes were blown N and NW, causing fine ashfall in parts of Rabaul Town. During the report period, seismicity was at low-to-moderate levels. GPS measurements of ground deformation showed no significant changes, but electronic tiltmeters showed minor inflation. RVO stated that the current eruption at Tavurvur is expected to continue, but an increase in eruptive activity is unlikely.
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.