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). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 10:12. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198512-252120.
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 north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W-trending 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.