During this week, aviation sources reported Ulawun ash plumes. A 30 April volcanic ash advisory detected a possible narrow low-level plume extending ~50 km from Ulawun. Satellite imagery for 2 May indicated an ash-and-steam plume rising to ~4 km and blowing W at ~30 km/hour. The plume extended 80 km W of the summit.

Sources: Darwin Volcanic Ash Advisory Centre (VAAC), US Air Force Weather Agency

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.