Report on Ulawun (Papua New Guinea) — September 1991

Bulletin of the Global Volcanism Network, vol. 16, no. 9 (September 1991)
Managing Editor: Lindsay McClelland

Ulawun (Papua New Guinea) Increased seismicity but surface activity limited to gas emission

Please cite this report as:

Global Volcanism Program, 1991. Report on Ulawun (Papua New Guinea). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 16:9. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199109-252120.

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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)


Increased seismicity has been observed at Ulawun, but surface activity remained limited to release of small to moderate volumes of white vapor until late September. Recorded seismicity since mid-August has consisted of numerous to nearly continuous, very small, low-frequency events. Larger events began to occur in mid-September. Periods of stronger seismic activity were occasionally separated by intervals of little seismicity, producing a banded appearance on seismograms. Similar seismicity has been recorded previously at Ulawun, and at Karkar prior to its 1979 eruption. Gas emission on 29 and 30 September was stronger, and brown plumes were reported.

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: P. de Saint-Ours and C. McKee, RVO.