The Rabaul Volcano Observatory (RVO) reported that seismicity at Ulawun increased at around 1600 on 19 November and was characterized as an increase in the magnitude of events resembling volcano-tectonic signals. Signals indicating volcanic tremors increased at around 1830 on 20 November, increased again at around 2015, and then slightly decreased and continued at that level. RVO recommended a declaration of Alert Level Stage 1 (the lowest level of a four-stage 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)