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Report on Rabaul (Papua New Guinea) — 8 November-14 November 2006


Rabaul

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 8 November-14 November 2006
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2006. Report on Rabaul (Papua New Guinea) (Sennert, S, ed.). Weekly Volcanic Activity Report, 8 November-14 November 2006. Smithsonian Institution and US Geological Survey.

Weekly Report (8 November-14 November 2006)

Rabaul

Papua New Guinea

4.271°S, 152.203°E; summit elev. 688 m

All times are local (unless otherwise noted)


RVO reported that during 25 October-1 November, Rabaul emitted thick white vapor and sub-continuous gray ash clouds. Fine ashfall was reported from areas N and NW, including Rabaul town. On 28 October, a large explosion produced an ash cloud that reached an altitude of 2 km (6,600 ft) a.s.l. and drifted NW. Fine ashfall was reported from areas downwind and lava fragments fell onto the flanks. Only continuous, thick, white vapor clouds were emitted during 1-7 November. Two explosive events occurred on 2 November. Ash plumes from the first explosion reached altitudes of 1.5 km (4,900 ft) a.s.l. Plumes from both explosions drifted N. During 3-10 November, occasional small-to-moderate ash emissions produced plumes that drifted SE, away from populated areas. During 11-13 November, thick white vapor and occasional gray ash clouds drifted SE, S, W, NW, and N. Fine ashfall was reported downwind on 11 November.

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 asymmetrical 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 1,400 years ago. An earlier caldera-forming eruption about 7,100 years ago is thought to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the N and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and W 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)