RVO reported that during 16 June-14 July white-to-light-gray plumes sometimes containing fine ash rose at most 2 km from Rabaul caldera's Tavurvur cone and drifted NW and SE. Roaring and rumbling noises also continued, and seismicity was low. Ashfall was reported in areas downwind including Rabaul town (3-5 km NW) during 16-30 June. The lava dome on the crater floor of Tavurvur continued to glow; on 26 June and 4 July observers near the dome noted brief incandescence at the vent associated with strong and rapid venting. Explosions during 10-14 July generated dense gray ash clouds that drifted NW, causing ashfall between Namanula Hill (3 km W) and Malaguna No.1 (NW), and Pilapila and Tavui Point.

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)