Report on Ulawun (Papua New Guinea) — December 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 12 (December 1985)
Managing Editor: Lindsay McClelland.
Ulawun (Papua New Guinea) Seismic and eruptive activity decrease in December
Please cite this report as:
Global Volcanism Program, 1985. Report on Ulawun (Papua New Guinea) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:12. Smithsonian Institution.
Papua New Guinea
5.05°S, 151.33°E; summit elev. 2334 m
All times are local (unless otherwise noted)
"Following the eruption of 17-28 November, seismicity at Ulawun remained at a moderately high level for the first half of December (500-1,000 events per day). By the end of the month seismicity had almost dropped back to pre-eruption levels.
"There were no further indications of eruptive activity except for a brief period of weak glow from the summit reported on the night of 2 December. Reports of eruptive activity from the Ulamona Mission on the 4th were probably due to a delayed debris avalanche. Unconsolidated material in the summit area became unstable and flowed down the NW flank. Loose ash was stirred up by the flow and produced an 'eruption-like' plume."
[This report was not included in GV 75-85.]
Geologic Background. 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.