The eruptive activity at Tavurvur that began in early October 2002 ceased on 17 February 2004. From 1-17 February the activity was characterized by emissions of light to pale ash clouds accompanied by occasional moderate explosions that produced thick ash plumes. The ash plumes rose 1000-2000 m above the summit before being blown to the E and NE resulting in ashfall in the Duke of York islands, ~ 30 km E of Rabaul.

A slight change in wind direction resulted in fine ashfall over Rabaul Town and villages downwind on 6 and 13-15 February. Occasional weak roaring noises accompanied some of the explosions on 5 and 11 February. From 18 February until the month's end, Tavurvur was only releasing weak white vapor, with occasional blue vapor. Seismic activity between 1 and 17 February reflected the ash emissions at the summit. One high frequency event occurred on 5 February, located NE of the caldera. Ground deformation indicated a deflationary trend. The real-time GPS and electronic tilt site on Matupit Island, in the center of the caldera, showed a deflationary trend since the middle of the month.

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: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.