Report on Kanlaon (Philippines) — February 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 2 (February 1985)
Managing Editor: Lindsay McClelland.
Kanlaon (Philippines) Steam and ash eruption follows local seismicity
Please cite this report as:
Global Volcanism Program, 1985. Report on Kanlaon (Philippines). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 10:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198502-272020.
10.412°N, 123.132°E; summit elev. 2435 m
All times are local (unless otherwise noted)
A small steam and ash eruption 13-14 March was preceded by local seismic activity. Three high-frequency volcanic tremors were recorded on 9 March and one each on 10, 11, and 12 March by a PHIVOLCS seismograph 9 km from the vent. Sustained seismic activity started suddenly on 13 March at 1312, 4.5 hours before the onset of the eruption, and totaled 139 recorded events, 60 of which were high-frequency and 79 low-frequency types. At the beginning of the seismic crisis, only high-frequency tremors were recorded, then low-frequency types predominated between 1400 and 1600. The number of events per minute declined before the eruption began.
Mild ejection of steam with a minimal amount of ash started 13 March at 1745, producing a plume that reached 300-500 m height. At 1515 the next day, the summit was steaming voluminously, and the vapor column rose 500-700 m. On 15 March at 1700, "moderate" steaming was reported. The volcano was cloud-covered and only occasionally visible. During the eruption's first 24 hours (until 14 March at 1759) 51 high-frequency and 9 low-frequency tremors were recorded.
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: PHIVOLCS, Quezon City.