RVO reported that roaring and rumbling noises from Rabaul caldera's Tavurvur cone began at 2128 on 19 January and lasted for about 15 minutes. Darkness prevented visual observations but the next day ash emissions were evident. On 20 January small discrete explosions generated ash clouds that rose up to 500 m above the crater and drifted E and SE. A few days before the eruption an observer noticed that vegetation on the N flanks of South Daughter (Turangunan, ~2 km to the E) had browned, and on 18 January a climber reported a strong sulfur dioxide odor.

A loud explosion at 2325 on 20 January was followed by a few minutes of continuous roaring and rumbling. During 20-22 January light gray ash emissions occurred at irregular intervals; the color of the plumes suggested mostly water vapor with low ash content. Plumes rose 200 m and drifted ESE on 20 January, and SW, S, and SSE on 21 January. Activity increased during 21-22 January with more frequent ash emissions occurring for extended periods. According to a news article, flights to Tokua airport were cancelled on 21 January.

Emissions subsided in the afternoon of 22 January but small-to-moderate explosions continued. A large explosion at 2147 ejected incandescent fragments, and produced an ash plume that rose 2 km and drifted SE and ESE. Explosions were heard through the night. Ash plumes that rose from the crater on 23 January drifted SE.

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), adelaidenow