During the week of 22-28 August 2005, Ulawun often remained quiet but also displayed continued restlessness. People from Tauke, on the S side of the volcano reported occasional low roaring, rumbling, and booming noises on 21-22 and 26-28 August. Emissions from the summit crater consisted of moderate volumes of thick grayish vapor released forcefully. Some traces of blue vapor were also visible, but no glow was observed. Seismicity fluctuated between low and moderate, marked by small low-frequency earthquakes and small sporadic volcanic tremors. Only one high-frequency earthquake was recorded. An earthquake was felt on 22 August by people from Tauke. Apparently the earthquake was not reported by the observer at Ulamona, NW of the volcano, suggesting it was local and focused on the S side of the volcano.

Ulawun remained quiet through mid-September 2005, with the summit crater releasing weak to moderate volumes of thick white vapor.

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: Rabaul Volcano Observatory, Papua New Guinea.