The Rabaul Volcano Observatory (RVO) reported that activity at Ulawun was low during 1-7 April. Summit emissions were characterized as white, having variable densities, and containing small amounts of ash. The plumes drifted S and caused minor ashfall in areas within a few km to the S and SW of the volcano. Low rumbling noises were heard in those same areas on 1 and 4 April. Seismicity generally remained low. The seismic station (UULA), 2.8 km from the summit on the lower WSW flank, recorded small low- and high-frequency volcanic earthquakes, with low-frequency earthquakes being the dominant signal. Starting at about 0800 on 4 April the seismic signals quickly changed to continuous volcanic tremor and the tremor amplitude grew relatively rapidly. The tremor lasted about 5.5 hours, reverting to discrete seismic signals at around 1720. The station ceased being operational at around 1900. The two other seismic stations, UALB (5.6 km) and UULB (10 km NW), did not detect the seismicity due to their distance from the volcano and high levels of cultural noise that obscured signals. RVO noted that a team from the West New Britain Provincial Disaster Office had been conducting community awareness activities within 10 km of Ulawun since 27 March, so far visiting the Ulamona area (10 km NW), Navo, Noau, Voluvolu, Bakada, Sabalbala, Vamakuma, Bago, Kabaia, Soi, and Sohula care center.

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)