RVO reported that during 27 March-2 April white and occasionally gray or brown plumes from Rabaul caldera's Tavurvur cone rose 1 km above the crater. Plumes drifted SE and NW. Incandescence from the summit crater was seen at night and roaring noises were reported. On 2 April, light ashfall was reported in Rabaul town (3-5 km NW) and surrounding areas. Based on analysis of satellite imagery, the Darwin VAAC reported that on 5 April an ash plume rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted about 37 km NE. On 7 April, ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted NW.

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.

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