RVO reported that during 1 September-15 October white vapor plumes with varying densities rose from Ulawun, although on 12 October pale gray ash plumes rose from the vent. A report from officers at Hargy Palm Oil dated 13 October stated that a “minor eruption” had occurred after 1800 on 12 October, and that there were a few low noises from the volcano and nighttime glow during 12-13 October. RVO noted that the seismic record did not indicate an eruption.

Seismicity was at a low to moderate level, dominated by small low-frequency volcanic earthquakes. RSAM values increased and by mid-October were at the highest values (peak of 200) so far in 2016. Based on analyses of satellite imagery, the Darwin VAAC reported that during 16-17 October ash plumes rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted SW and W.

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)