The quoted material is a report from RVO, with additional information on SO₂ flux supplied by S. Williams. "Throughout July, the volcano quietly released moderate, sometimes strong, white with occasional grey or brown emissions (on the 15th, 16th, 22nd, and 24th). Volcano seismicity remained at a low level with 10-30 small discrete B-type events/day."

During airborne COSPEC measurements on the 27th from 1150 to 1240, a diffuse white plume extended 10-15 km from the crater. Four traverses yielded SO₂ emission rates of 149, 66, 120, and 134 t/d. The average flux was 120 t/d, an increase from 1983 values (97, 70, 49, 66 t/d) that yielded an average of 70 t/d. When Williams flew past the volcano on 30 July, the plume remained thin, white, and wispy, but visible for 10-20 km downwind.

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: B. Talai and C. McKee, RVO; S. Williams, Louisiana State Univ.