Pago volcano, New Britain, Papua New Guinea
Brief report and photographs
Aug.26-September 2, 2002

Photos taken by M. Yoshimoto (VRC-ERI, Univ. tokyo)

When use the text and images pasted here, should contact us and show the credit of them.
Volcano Research Center, ERI, Univ. Tokyo --- updated, September 4, 2002
Outline: The Japanese Disaster Relief Team, including of two seismologists, Drs. K. Uhira and A. Takagi, JMA and a geologist Dr. Mitsuhiro Yoshimoto, University of Tokyo, was dispatched to Pago volcano, New Britain, Papua New Guinea, according to the friendly relations between PNG and Japan, during Aug 25-Sept. 3. The observation was carried out, being supported by Rabaul Volcano Observatory (RVO), PNG, and governmental agencies of the both countries, including Japan International Cooperation Agency (JICA). Details of the eruption will be prepared by RVO.

NW view of new lava flows and Pago cone (Aug. 29, 2002)

Map showing distribution of new lava flows (red), compared with the previous lava flows (1911-33).

Helicopter used for air inspection and transportation.

Seismic obsevation by JMA scientists, about 3 km SW of the summit.

New lava samples were collected from the flow front.

New lava sample (dacite!) collected by M. Yoshimoto

General statement: The post-cadera lava shield of Pago is in striking morphological contrast to the pre-caldera volcano, Witori, a low-angle dominantly pyroclastic structure (Blake 1976). Cook (1981) introduced that Pago volcano is a DACITIC lava shield and the SiO2 is about 66 %. (Refferences: Blake, D.H. (1978) Volcanism in Australia, 191-200, Elsevier., Cooke, RJS (1981) Geol. Surv. PNG Memoir 10, 135-146).
Lava effusion started on August 5, 2002, following about one-month seismic activity. According to the eywitness accounts of local people, about ten times of puffing of volcanic ash took place till August 14. The new lava was also about 66 % SiO2 according to the prelimary analysis in N.Z. by C. McKee (RVO). The present eruption is smaller in scale than the 1911-1933 eruption so far.











Explanations of photographs

Dsc0 1813. Crater line extending to NW (this side) from the Pago Central Cone. The lava flow farthest from the cone (lowest) is not shown in this image.
Dsc0 1839. New lava (oxidized)
Dsc0 1872. Seen from the south of the central cone.
Dsc0 1878. NW-most lava flow.
Dsc0 1883. Central cone and the new craters.
Dsc0 1906. Central cone and the new craters.
Dsc0 1907. Crater line and lava (1)
Dsc0 1908. Crater line and lava (2)
Dsc0 1910. Crater line and lava (3).
Dsc0 1911. Fault perpendicular to the crater line.

Work schedule of Japanese Team

Aug. 26: Arrived at Kinbe/PNG (leave Tokyo on Aug. 25). Meeting w/ RVO.
Aug. 27: Air inspection from helicopter and survey of air-fall tephra
Aug. 28: Sampling was cancelled. Survey of air-fall. Seismometer installation.
Aug. 29: Rock sampling, climbing the Pago summit.
Aug. 30: Air inspection and recovery of seismometer.
Aug. 31: Rock sampling and suvey of air-fall tephra.
Sept. 1: Meeting w/RVO and preparing reports
Sept. 2: Leave Kinbe/PNG (Tokyo on Sept. 3)

Geological brief notes----------Trial hazard map for ash falling, prepared by Drs. El-Kherbotly and Macatol

1. Five craters are aligned in the NW-SE direction from the middle slope NW the Pago Central Cone to the Witori caldera caldera.
2. New lava descended from four craters except from the highest one. The largest amount of lava did from the lowest one, still moving, changing its flowing direction into NE and SW due to the caldera wall.
3. No eruption column was seen, though bluish white-colored fumarolic gas was emitting. Sulfur was deposited on the crater rim.
4. A fault perpendicular to the crater line could be seen in the middle of and W of the rater line.
5. RVO,had observed another fault parallel to the crater line N of this fault.
6. The thickness of air fall deposit is about 2 mm at a place 3 km N of the craters, and less than 1 mm at the Hoskins Air Port.

Thermal and gas observation ---------Thermal image from NW on August 28 (taken by K. Uhira and A. Takagi)

1. The lowest lava flow lobe (NW-most lobe) is still moving, keeping high temperature. Thermal images with the infrared camera from helicopter gave the temperature of 350 degrees C at the emittion point (vent).
2. The other lava flow lobes had been cooled. These probably stopped before August 14, because they are covered with tephra of this eruption.
3. SO2 abundance inside the caldera is high; 30 ppm near the lava front.

Seismic observation

1. A seismometer with three components had been set about 3 km SW of the summit. Seismic signals during about 40 hours were recorded.
2. Small earthquakes had occurred steadily 20 to 30 times an hour, suggesting continuous effusion of lava from the vent. No notable swarms of earthquakes were detected during observation.
3. Low frequency (3-4 Hz) and high frequency (8-10 Hz) earthquakes and tremor-like signals were included. Tremor-like signals may result from rock falling.
4. The P-S time of about 1.6 second and polarity of first motions suggest that seismic waves came from the lava flow vent.

Perspectives and recommendaion:

As far as being observed these days, the present state of Pago volcano is rather stable, and it is very unlikely that a large eruption such as sending a huge column of eruption cloud will occur soon. Small puffing of ash is still possible. When felt-earthquakes begin, being associated with an intense ground deformation such as growing cracks to the basement rocks and steadily growing bulging of the crater area, however, it is the possibility that an explosive eruption may take place. Therefore, continuous monitoring by means of field inspection, seismic observation and geodetic observation such as EDM is needed until waning of the eruptive activity becomes evident. Mud flow is probable in a rainy season that starts soon.


The Japanese Disaster Relief Team extends hearty thanks to Mr. Clement Nakmai, Governor of West New Britain and Mr. William Padio, Administrator of West New Britain for the warm hospitality. Thanks are also to Drs. Hassan El-Kherbotly and Isolde Macatol and Mr. Ima Itikarai for great assistance to the research acitivty.

Infomation contact: Mitsuhiro Yoshimoto (VRC-ERI, University of Tokyo);, Koichi Uhira and Akimichi Takagi (JMA);,, and VRC-ERI, University of Tokyo;

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