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Report on Rabaul (Papua New Guinea) — May 1990


Rabaul

Bulletin of the Global Volcanism Network, vol. 15, no. 5 (May 1990)
Managing Editor: Lindsay McClelland.

Rabaul (Papua New Guinea) Slight increase in seismicity; minor deformation near center of caldera

Please cite this report as:

Global Volcanism Program, 1990. Report on Rabaul (Papua New Guinea) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199005-252140



Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


"Seismicity was [moderate] in May, with 234 caldera earthquakes recorded. Most located events originated from the N part of the annular caldera seismic zone. Levelling measurements on 31 May showed that the S part of Matupit Island . . . had been uplifted ~17 mm since the previous measurements (25 April). However, there were no significant changes in tilt and EDM measurements."

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.

Information Contacts: P. de Saint-Ours and C. McKee, RVO.