Report on Kanlaon (Philippines) — January 2002
Bulletin of the Global Volcanism Network, vol. 27, no. 1 (January 2002)
Managing Editor: Richard Wunderman.
Kanlaon (Philippines) Increased seismicity during January 2002 may be precursor to eruption
Please cite this report as:
Global Volcanism Program, 2002. Report on Kanlaon (Philippines) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 27:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200201-272020.
10.412°N, 123.132°E; summit elev. 2435 m
All times are local (unless otherwise noted)
As of late May 2001, seismicity at Canlaon was low, and the Philippine Institute of Volcanology and Seismology (PHIVOLCS) relaxed its no-entry advisory into the crater (BGVN 26:10). No further reports were issued through 2001.
On 30 January 2002 PHIVOLCS reported that during the previous month, the seismic network around the volcano detected a higher number of earthquakes, observations that may indicate a reactivation of the volcano. Seismicity was dominated by high-frequency earthquakes located around the crater, from shallow depth to 8.5 km deep. These earthquakes may represent episodes of subsurface fracturing due to magma intrusion. During mid-January, PHIVOLCS further noted the occurrence of several low-frequency earthquakes, which supports the idea that some fluid migration, possibly magma ascent, was occurring. PHIVOLCS noted that if this idea was confirmed by forthcoming surveys, then the Alert Level may be raised.
Increased activity at Canlaon was recognized as early as January 2001 with occurrences of earthquake clusters. At the time PHIVOLCS issued a similar notice but activity quieted down. This year's reactivation seems more intense in terms of the number of earthquakes. They could foretell of impending phreatic eruptions. Several teams were sent to augment the Canlaon Volcano Observatory with additional seismometers and deployment of a GPS-based ground-deformation monitoring network. Because sudden phreatic or steam-driven explosions may occur at any time, PHIVOLCS urged the public to strictly observe the 4-km-radius Permanent Danger Zone (PDZ) around the volcano and recommended the suspension of all treks within this zone until further notice. As of 30 January, PHIVOLCS reported that volcanic activity did not require any kind of evacuation except for areas within the PDZ.
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 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 SW from Kanlaon. The summit 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, 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.