Ulawun remained relatively quiet from mid-September 2005, the date of our last report (BGVN 30:09), until 1-2 March 2006 when strong, forcefully expelled "gray-blue emissions" were observed from the main crater. There may also have been incandescence at the base of the plumes. There were no emissions from the NW vent. Small, felt earthquakes occurred and the sound of roaring was heard by nearby villagers. According to the Darwin VAAC, RVO reported that ash reached ~ 3 km (10,000 ft) altitude on 1 March. However, ash was not visible on satellite imagery.

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: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Andrew Tupper, Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).