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 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.

Source: Rabaul Volcano Observatory (RVO)