Report on Rabaul (Papua New Guinea) — February 2010
Bulletin of the Global Volcanism Network, vol. 35, no. 2 (February 2010)
Managing Editor: Richard Wunderman.
Rabaul (Papua New Guinea) Quiet during early 2010 with few emissions or earthquakes; 2008 summary
Please cite this report as:
Global Volcanism Program, 2010. Report on Rabaul (Papua New Guinea). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 35:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201002-252140.
Papua New Guinea
4.271°S, 152.203°E; summit elev. 688 m
All times are local (unless otherwise noted)
This report discusses quiet at Tavurvur cone during the first quarter of 2010. Reports only covered parts of the reporting interval, 1 January to 8 April 2010. A report discussed in a subsection below provides an overview for 2008, including ashfall, mudflow, aviation, stress on inhabitants, and monitoring instruments. Our previous report noted intermittent ash plumes and incandescent ejections during 2009 (BGVN 34:11).
According to the Rabaul Volcano Observatory (RVO), ash emissions were absent on most days at Tavurvur cone during 1-25 January 2010, but steam plumes, white to blue in color were occasionally seen. Approximately three brown-gray ash clouds were produced on 3 January. Minor ash emissions on 8 January rose less than 200 m above the cone. A few small low-frequency earthquakes took place during 1-10 January, but they then remained absent through at least 25 January. Volcano-tectonic earthquakes were noted on 8 and 14 January. One ash cloud was noted on 31 January. GPS measurements and tide gauge data continued to show minor uplift?rates of ~ 1 cm every 1 to 2 weeks during January 2010.
Based on information from the United Kingdom's National Weather Service office in Port Moresby, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that on 18 January, an ash plume from Tavurvur cone rose to 2.4 km altitude.
RVO reported that during 21-27 February and 2-8 April, the volcano was quiet with small-to-moderate volumes of white vapor emissions and small low-frequency earthquakes. During the later interval the cone was not emitting ash and sulfur dioxide (SO2) fluxes remained at the lowest levels since measurements on the gas began in June 2009. After intervals of rainfall, steam emissions became voluminous.
RVO advised people to avoid entering the crater because of slope instability and gas accumulation in low lying areas. As of early 2010, the last posted MODVOLC thermal alerts at Rabaul took place 24 November 2009.
Summary of 2008 activity. Although Bulletin reports covered the year 2008 (BGVN 33:03, 33:11, 34:08), a recent report (Arumba, 2009) provides an authoritative summary touching on a broader range of topics.
Arumba (2009) stated that "Tavurvur ... erupted throughout 2008. The level of eruption was relatively mild during the first half of the year, but this changed during the second half when the mode of eruption changed from sporadic ash emissions occurring at long intervals to almost sub-continuous emissions. Between July and October/November SE winds blew the ash-rich plumes towards Rabaul Town and the surrounding areas and deposited significant volumes of ash and affected the everyday livelihood of people and gave rise to the emergence of health-related issues. The ash deposits turned into mudflows as soon as rain began to fall in October and severely affected the entire town of Rabaul and the surrounding areas.
"The eruption also affected the domestic aviation industry when ash-rich plumes frequented the air space of the flight path and deposited considerable amounts of ash on the runway. A flight service to the only main airport that serves East New Britain Province was disrupted, severely affecting the traveling public.
"The seismic monitoring network at Rabaul was maintained at a reasonable level. A couple of stations which had been off from the start of 2008 were restored. The tide gauge network consisting of three stations was partially restored after a long period of inactivity. An upgrade of the real-time Global Positioning System (GPS) of four stations for deformation measurements began during the last quarter of the year. By the end of the year three of the stations were restored . . . ."
Reference. Arumba, J., 2009, Agenda Item 3, Coordinating Committee for Geoscience Programmes in East and Southeast Asia (CCOP), 46th CCOP Annual Session, 18-23 October 2009, Vungtau, Vietnam; Member Country Report of Papua New Guinea, October 2009, Annual member country report, 16 p.
Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.
Information Contacts: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).