Report on Ulawun (Papua New Guinea) — July 1983

Scientific Event Alert Network Bulletin, vol. 8, no. 7 (July 1983)
Managing Editor: Lindsay McClelland

Ulawun (Papua New Guinea) Strong seismicity but no change in plume

Please cite this report as:

Global Volcanism Program, 1983. Report on Ulawun (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 8:7. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198307-252120.

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Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


"The moderate white vapour plume released at Ulawun's summit crater was undisturbed by the volcano's continuing unstable seismicity. A seismic crisis that started on 26 June was the longest since March when this pattern of activity started. It consisted of several periods of tremor up to 13 hours long, and sub-continuous volcanic earthquakes. This activity declined progressively 2-3 July to return to a rate of 1000-1500 B-type events per day. However, the average amplitude of discrete events remained fairly high (about 3 times normal levels) until 20 July. Further seismic crises on 16, 17, and 19 July marked the end of this particular period of stronger seismicity. No significant tilt changes were evident in July."

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. Ulawun 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 of the 2334-m-high Ulawun volcano 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 eastern flanks. A steep-walled valley cuts the NW side of Ulawun volcano, 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. de Saint Ours, RVO.