Report on Witori (Papua New Guinea) — 7 August-13 August 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
7 August-13 August 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Witori (Papua New Guinea). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 7 August-13 August 2002. Smithsonian Institution and US Geological Survey.
Papua New Guinea
5.576°S, 150.516°E; summit elev. 724 m
All times are local (unless otherwise noted)
The eruption at Pago that began the previous week continued through 13 August. According to news articles, 6,000-8,000 people had been evacuated from villages surrounding the volcano by 9 August. No injuries had been reported. The Rabaul Volcano Observatory (RVO) reported that the eruption was characterized by the ejection of light gray to some dark ash clouds. The clouds drifted primarily to the N and NW, after reaching heights of a few kilometers above the summit. Very little ash was deposited in areas surrounding the volcano. The thickest ashfall (3 mm) occurred at Rikau and Matmada, 6-8 km NNW of the volcano. There was not more than 1 mm of ash deposited at Hoskins airport. Aerial inspection of the summit area by RVO staff indicated that there were no lava flows descending the volcano's flanks, instead, lava extruded onto the surface formed cones above the active vents. The highest cone was about 60 m tall. Contrary to previous reports, there was no bulging on the N or NW sides of the volcano. During the week, seismicity was at low-to-moderate levels. The closure of the airport near the town of Kimbe, 30 miles N of Pago, disrupted island air traffic. On 13 August at 1030 a thin plume was visible on satellite imagery reaching a height of about 2.1 km and extending N to NW. The summit was covered by meteorological clouds, preventing visual observations. Only weak intermittent rumbling was heard. RVO advised that activity had settled into a steady pattern, although changes in the nature of the eruption could occur.
Geological Summary. The Witori caldera (5.5 x 7.5 km) on the northern coast of central New Britain contains the active Pago cone. The Buru caldera cuts the SW flank. The gently sloping outer flanks consist primarily of dacitic pyroclastic-flow and airfall deposits produced during a series of five major explosive eruptions from about 5,600 to 1,200 years ago, many of which may have been associated with caldera formation. The post-caldera Pago cone may have formed less than 350 years ago; it has grown to a height above the Witori caldera rim, and a series of ten dacitic lava flows from it covers much of the caldera floor. The youngest of these was erupted during 2002-2003 from vents extending from the summit nearly to the NW caldera wall.