RVO reported that on 27 June diffuse white plumes rose from Ulawun’s summit crater and incandescence was visible from pyroclastic or lava flow deposits on the N flank from the significant eruption the day before. The seismic station located 11 km NW of the volcano recorded low RSAM values between 2 and 50. According to the Darwin VAAC a strong thermal anomaly was visible in satellite images, though not after 1200. Ash from 26 June explosions continued to move away from the volcano and became difficult to discern in satellite images by 1300, though a sulfur dioxide signal persisted; ash at 13.7 km (45,000 ft) a.s.l. drifted SW to SE and dissipated by 1620, and ash at 16.8 km (55,000 ft) a.s.l. drifted NW to NE and dissipated by 1857. RVO noted that at 1300 on 27 June satellite images captured an ash explosion not reported by ground-based observers likely due to cloudy weather conditions. The Alert Level was lowered to Stage 1.

RSAM values slightly increased at 0600 on 28 June and fluctuated between 80 to 150 units afterwards. During 28-29 June diffuse white plumes continued to rise from the crater and from the North Valley vent. On 29 June a news article stated that around 11,000 people remained evacuated to shelters.

Geological Summary. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

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