Report on Ulawun (Papua New Guinea) — April 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 4 (April 1989)
Managing Editor: Lindsay McClelland.
Ulawun (Papua New Guinea) Small ash emissions, minor seismic increases
Please cite this report as:
Global Volcanism Program, 1989. Report on Ulawun (Papua New Guinea). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 14:4. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198904-252120.
Papua New Guinea
5.05°S, 151.33°E; summit elev. 2334 m
All times are local (unless otherwise noted)
"Mild, intermittent, eruptive activity continued in April. Ash emissions occurred 6, 8, 11, 20-22, and 28 April, but their ash content was low, and no significant ashfalls were reported. A strong correlation between activity and preceding heavy rainfall (as observed in March) was not evident. When not producing ash, the volcano emitted white vapours at moderate rates.
"For most of the month, the volcano-seismicity consisted of occasional, small, low-frequency events. Periods of low-amplitude, discontinuous and irregular tremor were recorded between 16 and 18 April. During the last week of April (perhaps correlating with a period of moderate rainfall) discrete events were more numerous, with periods of continuous and discontinuous irregular tremor of low-moderate amplitude."
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, RVO.