Typical activity at Ulawun consists of sporadic explosions with weak ash plumes. During 2017, sporadic explosions occurred between late June through early November with ash plumes rising no more than 3 km in altitude (BGVN 42:12). This report describes activity between January and September 2018.

According to the Darwin Volcanic Ash Advisory Centre (VAAC), a NOTAM (Notice to Airmen) stated that on 8 June 2018 an ash plume rose to an altitude of 2.1 km and drifted W. The Darwin VAAC also reported that a pilot observed an ash plume on 21 September 2018 rising to an altitude of 3.7 km and drifting W. Ash was not confirmed in satellite images, though weather clouds obscured views.

On 5 October 2018 the Darwin VAAC identified a steam-and-ash emission in satellite images rising to an altitude of 4.6 km and drifting WSW. It was also reported by ground observers. The Rabaul Volcano Observatory reported that during 1-12 October white, and sometimes light gray, emissions rose from the summit crater; seismicity was low.

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.

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea.