When visible, the summit crater was releasing moderate amounts of white vapour during December. The daily totals of volcanic earthquakes increased on 2 December and averaged ~150 until the 17th. A further, but somewhat irregular, increase began on the 18th and reached a peak of ~800 events/day on 23 and 24 December. Earthquakes then decreased steadily, stabilizing at ~350 events/day after 26 December. The summit was obscured throughout most of the period of increased seismicity.

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: C. McKee and P. Lowenstein, RVO.