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 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.

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