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Report on Rabaul (Papua New Guinea) — 27 July-2 August 2011


Rabaul

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 27 July-2 August 2011
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2011. Report on Rabaul (Papua New Guinea) (Sennert, S, ed.). Weekly Volcanic Activity Report, 27 July-2 August 2011. Smithsonian Institution and US Geological Survey.

Weekly Report (27 July-2 August 2011)

Rabaul

Papua New Guinea

4.2459°S, 152.1937°E; summit elev. 688 m

All times are local (unless otherwise noted)


RVO reported that white vapor occasionally tinted blue rose from Rabaul caldera's Tavurvur cone during 1-28 July. Dull incandescence emanated from a small caved-in vent on the floor of the crater. The start of an ash eruption on 29 July was marked by an emergent low-frequency tremor and slowly rising gray ash plumes. One explosion on 30 July possibly produced light ashfall to the NW. Seismic data indicated forceful degassing on 1 August.

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)