Ash emissions and sporadic seismicity at Canlaon between March 2003 and March 2004 were reported in BGVN 29:12. A brief ash emission began at Canlaon around 0930 on 21 January 2005. The eruption cloud rose ~ 500 m above the active crater and drifted WNW and SW. No coincident volcanic earthquakes were recorded. Fine ash was deposited in the city of Cabagnaan, ~ 5.5 km SW of the crater. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) advised the public to avoid entering the 4-km-radius Permanent Danger Zone around Canlaon.

Ash emissions began again on 20 March around 1300. Small amounts of ash fell in the town of Guintubdan 5 km W of the volcano. During 24 March to 4 April, sporadic ash emissions rose to a maximum of 1 km above the volcano. During this time ash fell in the towns of La Castellana (16 km SW of the crater), Upper Sag-ang, Yubo (5-6 km SW), and Guintubdan (5-6 km WNW). Due to this unrest, PHIVOLCS raised the Alert Level from 0 to 1 (on a scale of 0-5) on 30 March. According to a news article, pilots were advised to avoid flying near Canlaon.

On March 22 the Provincial Disaster Management Team (PDMT) warned it would apprehend trekkers and faith healers who ventured to Mount Canlaon during Holy Week. Trekking to Mount Canlaon has become a practice by some faith healers and mountaineers who believe that the volcano is a source of supernatural powers.

On 31 March at 0601 and 1715, two mild ash ejections reached heights of about 200-300 m above the summit before drifting NW and SW. Ash was deposited at Guintubdan, Upper Sag-ang, and Upper Mansalanao. A low-energy ash emission on 7 April at 1429 generated a cloud which rose to a height of ~ 100 m above the crater and drifted SW. According to PHIVOLCS, the seismic monitoring network around the volcano did not record any earthquakes during this event. During 13-14 April, mild ash emissions produced plumes to a height of ~ 700 m above the crater. During 15-17 April, moderate-to-strong emissions produced ash plumes to ~ 2 km above the crater and deposited ash in villages as far as La Castellana. None of these ash emissions was associated with seismicity, indicating that the activity is likely hydrothermal in nature, and taking place at shallow levels in the crater.

Throughout this period Canlaon remained at Alert Level 1. As of the end of April 2005, the 4-km-radius Permanent Danger Zone (PDZ) was restricted and all treks to the summit remained suspended.

Geological Summary. Kanlaon volcano (also spelled Canlaon) forms the highest point on the island of Negros, Philippines. The massive andesitic stratovolcano is covered 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 active vent, Lugud crater, to the south. Eruptions recorded since 1866 have typically consisted of phreatic explosions of small-to-moderate size that produce minor local ashfall.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, PHIVOLCS Building, C.P. Garcia Avenue, Univ. of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Chris Newhall, USGS, Box 351310, University of Washington, Seattle, WA 98195-1310, USA; Philippine Star (URL: http://www.philstar.com/).