Rabaul Volcano Observatory (RVO) reported that small-to-moderate volumes of white steam-and-gas plumes were visible in webcam images rising from Ulawun’s summit during 4-6 August. On the rest of the days through 12 August weather conditions mostly prevented views of the summit. No audible sounds or nighttime crater incandescence were reported. RSAM fluctuated during 4 July-12 August but overall showed an upward trend and corresponded to an increase in volcanic tremor amplitudes. RVO warned that minor eruptive activity may occur if the trend continued and that ash emissions had previously occurred at similar RSAM levels. The Alert Level remained at Stage 1 (the lowest level on the four-level scale).

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.

Source: Rabaul Volcano Observatory (RVO)