Report on Ulawun (Papua New Guinea) — May 2001

Bulletin of the Global Volcanism Network, vol. 26, no. 5 (May 2001)
Managing Editor: Richard Wunderman.

Ulawun (Papua New Guinea) Eruption on 30 April 2001 sends an ash cloud to a height of ~13.7 km

Please cite this report as:

Global Volcanism Program, 2001. Report on Ulawun (Papua New Guinea). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 26:5. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200105-252120.

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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)


On 30 April 2001 a moderate-sized ash cloud from an eruption at Ulawun was visible on Geostationary Meteorological Satellite (GMS), U.S. National Oceanic and Atmospheric Administration (NOAA) weather satellite, and Total Ozone Mapping Spectrometer (TOMS) imagery. There had been no reports of anomalous volcanic activity at Ulawun since the 28 September-2 October 2000 eruption sent an ash cloud 12-15 km above the volcano (BGVN 25:11).

The Darwin VAAC received a pilot report that a "smoke" cloud had been emitted from Ulawun on 30 April at 0730. The Rabaul Volcano Observatory (RVO) confirmed the report. The cloud reached an altitude of ~9 km and drifted NW and SW, expanding to 80-113 km in radius. GMS and NOAA weather satellite imagery indicated that the cloud may have reached a maximum height of ~13.7 km and that the eruption ceased by approximately 1530. By 3 May volcanic activity had decreased, but, because further ash emissions could occur, RVO placed the volcano at Stage 2 Alert. RVO reported that limited evacuations occurred. Ash was not observed on satellite imagery after the 30 April eruption, although ash clouds may have been obscured by meteorological clouds near the volcano.

On 30 April around noon, a few hours after reports of an eruption at Ulawun, the Earth Probe TOMS detected a SO2 cloud over SW New Britain,. A gap between successive TOMS swaths over the volcano unfortunately precluded measurement of the full extent of this cloud. Elevated levels of SO2 were recorded in a region bounded approximately by longitudes 147°E and 150°E (swath edge) and by latitudes 5°S and 7°S, at a maximum distance of ~400 km WSW from Ulawun. The highest SO2 concentrations (38 milli atm cm) were recorded in a NNW-SSE trending region ~300 km WSW of the volcano. Preliminary analysis indicates that the portion of the cloud visible in TOMS imagery contained ~5 kilotons of SO2.

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: Darwin VAAC, Regional Director, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Simon Carn, Joint Center for Earth System Technology (NASA/UMBC), University of Maryland Baltimore County, 1000 Hilltop Circle Baltimore, MD 21250.