RVO reported that during 26 March-1 April, Rabaul caldera's Tavurvur cone emitted steam and steam-and-ash plumes that rose to 0.8 km (2,600 ft) a.s.l. and drifted E, N, and NW. Roaring noises occasionally accompanied emissions. Incandescent material was ejected to at most 100 m above the lowest part of the vent during 26-30 March. Based on reports from RVO and satellite imagery, the Darwin VAAC reported that ash plumes rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and drifted NE during 1-2 April.

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.

Sources: Darwin Volcanic Ash Advisory Centre (VAAC), Rabaul Volcano Observatory (RVO)