Canlaon (Philippines) Sudden phreatic explosion kills three people

Negros Islands, Philippines
10.410N, 123.130E; summit elev. 2,345 m
All times are local ( = GMT + 8 hours)

On 10 August 1996 at 1431 an ash ejection at Canlaon (also known as Kanlaon) killed three hikers and emitted a dirty-white steam-and-ash plume. The plume rose 1,500 m above the central crater at the volcano's summit. The ash ejection lasted about 24 minutes, based on seismic records. Accompanying the ash ejection was a small explosion-type earthquake (22.8 mm of amplitude at the PHIVOLCS Kabagnaan seismic station, 5.5 km SW of the volcano). The ejected ash drifted to NE and was observed at an altitude of 7.6 and 11.3 km by aviators. The Bureau of Meteorology - Darwin, issued a volcanic ash advisory, describing the plume as extending SW for 110 km. 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 the previous character of ash ejections of Canlaon, which were clustered in time, it was judged that the volcano could have more explosions without showing any additional forewarning signs. After the ash ejection, there were moderate emissions of white to dirty-white steam that rose 100 - 150 m before drifting NE. On 11 August more emissions of white steam were noted between the hours 0353 and 0500. A volcanic ash advisory issued by the Bureau of Meteorology on that day again reported the plume drifting SW.

The seismograph at Kabagnaan recorded a total of 23 low-frequency volcanic earthquakes and 4 tectonic earthquakes. A quick response team from PHIVOLCS was sent to set up additional seismic instrumentation and to closely monitor ground deformation and the eruptive activity.

According to 11 August Reuters Limited and Agence France Presse news reports, two mountaineering groups were present on the summit at the moment of the explosion. A group of students from a Belgian University and their Filipino guides, and two British visitors accompanied by a local guide. Three people, one British and two Filipino were killed. Some Belgians and Filipinos managed to make it off the mountain before darkness halted rescue efforts, but other survivors were forced to spend the night there and were retrieved the day after.

Some of the 18 survivors were hospitalized because of injuries caused mainly by falling ejecta. Belgian Caroline Verlinde told the 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 Filipino guide had reassured her that it was just ordinary. "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. Mountain guide Rey Estelloso, who escorted the group of Belgian students, blamed the young people's boisterous behavior, "When you are up there you are not supposed to make any noise or throw stones into the crater because you might disturb the spirits," he said, "I told them to keep quiet but they did not."

Canlaon stratovolcano, the highest point on the central island of Negros, is 510 km ESE of Manila. Since 1866, 14 historical eruptions are known; they typically consisted of small to moderate phreatic explosions. The last reported activity was a mild phreatic explosion on 25 August 1993. It produced a large volume of steam-and-ash, followed by minor steam emissions; fall was detected as far as 65 km W. Another phreatic explosion occurred on 3 September 1993 produced a grayish steam-and-ash column that rose 1,000 m above the summit. Both episodes were accompanied by an increase in seismicity (Bulletin, vol. 18, no. 8).

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, Darwin station; Agence France Presse (AFP); Reuters Limited. Rick Wunderman; Smithsonian's Global Volcanism Network (