Report on Witori (Papua New Guinea) — 31 July-6 August 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 31 July-6 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, 31 July-6 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)
Qantas Airlines reported that a rapidly increasing ash cloud was visible at 9.1 km a.s.l. on 3 August at 1440. The summit was obscured by clouds, so ash was not identifiable from satellite imagery. On 5 August at 0705 Air Niugini reported another ash cloud that was 18 km wide at 1.2 km a.s.l. extending 37 km NW. According to press reports, this plume was from an eruption that began on 5 August around 0530. By 0600, residents in Hoskins and Kimbe towns realized there had been an eruption when they saw thick clouds of ash drifting W across Kimbe Bay. Another eruption occurred about midday, raining ash on Hoskins. An estimated 10,000 to 15,000 people in villages at the foot of the volcano and surrounding areas could be affected by ashfall. Earthquakes were felt before the eruption.
Air Niugini reported that on 6 August at 0630 a 1.8- to 2.4-km-thick gray ash plume extended 148 km WNW at 7.6 km a.s.l. The Rabaul Volcano Observatory noted that at 0830 the ash column had reached 10 km above the volcano. A low-level ash plume identified on GMS visible satellite imagery at 0932 extended 111 km WNW with a width of 18 km. By 1132 the ash plume was 37 km wide based on visible satellite imagery. The Rabaul Volcano Observatory reported that eruptions were continuing on 6 August at 1800 with the ash plume moving NNW to N.
Geologic Background. The 5.5 x 7.5 km Witori caldera on the northern coast of central New Britain contains the young historically active cone of Pago. The Buru caldera cuts the SW flank of Witori volcano. The gently sloping outer flanks of Witori volcano consist primarily of dacitic pyroclastic-flow and airfall deposits produced during a series of five major explosive eruptions from about 5600 to 1200 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. Pago has grown to a height above that of 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.