Report on Kanlaon (Philippines) — July 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 7 (July 1996)
Managing Editor: Richard Wunderman.
Kanlaon (Philippines) Sudden phreatic explosion kills three people
Please cite this report as:
Global Volcanism Program, 1996. Report on Kanlaon (Philippines). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 21:7. Smithsonian Institution. https://dx.doi.org/10.5479/si.GVP.BGVN199607-272020.
10.412°N, 123.132°E; summit elev. 2435 m
All times are local (unless otherwise noted)
On 10 August at 1431 an ash ejection killed three hikers and emitted a dirty-white steam-and-ash plume to 1,500 m above the central summit crater. The ash ejection lasted ~24 minutes, based on seismic records. A small associated explosion-type earthquake (22.8 mm of amplitude) was detected at the PHIVOLCS Cabagnaan seismic station, 5.5 km SW of the volcano. The ash drifted NE and was observed at altitudes of 7.6 and 11.3 km by Qantas aviators. The Bureau of Meteorology in Darwin issued a volcanic ash advisory describing the plume as extending 110 km SW. PHIVOLCS established a Level 1 alert (low level of hydrothermal disturbance, without any indication of magmatic activity), but no evacuation was advised. PHIVOLCS promptly warned the public to stay outside the 4-km-radius permanent-danger buffer zone. Based on previous Canlaon ash ejections, which were clustered in time, it was judged that there could be more explosions without any additional precursors. After the ash ejection, moderate emissions of white to dirty-white steam rose 100-150 m before drifting NE. On 11 August more white steam emissions were noted between 0353 and 0500. Another aviation notice reported the plume drifting SW.
The Cabagnaan seismograph recorded a total of 23 low-frequency volcanic earthquakes and four tectonic earthquakes from 0600 on 11 August through 0600 on 12 August. During 12 August, a quick response team from PHIVOLCS had installed four seismographs and was monitoring ground deformation. The team was also planning to determine the extent of the ash deposit.
According to 11 August news reports, two mountaineering groups were present on the summit at the moment of the explosion: a group of ten students from a Belgian University and their seven Filipino guides, and two British visitors accompanied by two local guides. Three people, one British and two Filipino, were killed. Seven Belgians and four Filipinos were evacuated or managed to make it off the mountain before darkness halted rescue efforts, but the other survivors were not rescued until the next morning.
Some of the 18 survivors were hospitalized because of injuries caused mainly by falling ejecta. Belgian Caroline Verlinde told reporters that she was descending from the crater rim when the eruption began without warning. She said she had seen a plume of smoke but her guide reassured her that it was normal. "Suddenly it spewed ash and stones. I hid behind a tree but my friends had nothing to protect them. I saw stones falling on them," she told the reporters.
Geologic Background. Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive 2435-m-high andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km to the SW from Kanlaon. The summit of Kanlaon contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions from Kanlaon, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.
Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, 5th & 6th Floors, Hizon building, 29 Quezon Avenue, Quezon City, Philippines; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin, NT 0801, Australia; Agence France Presse (AFP); Reuters Limited.