The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 17-31 December. The seismic network recorded 8-26 daily volcanic earthquakes during 17-22 December, along with sulfur dioxide emissions ranging from 4,208 to 7,445 tonnes per day. Weather clouds mostly prevented views of the summit but on 18 December emissions were seen rising 100 m above the summit and drifting SW.

At 1145 on 23 December dark ash emissions began rising from the crater and were accompanied by low-frequency volcanic tremor. The plumes rose 1.2 km above the crater, drifted NW, and were continuous at least through 1230, when a special report was issued. Almost daily ash emissions occurred during 24-30 December; 2-9 periods of ash emissions each day except for 27 December ranged from three minutes to two hours and 26 minutes. The emissions rose as high as 1.2 km above the crater rim and drifted NW, W, SW, and SSW and were voluminous during 28-30 December. Seismicity was characterized by 16-25 daily volcanic earthquakes and 2-11 daily periods of tremor lasting as short as three minutes to as long as one hour and 32 minutes. sulfur dioxide emissions continued to be elevated, ranging from 2,200 to 7,705 tonnes per day.

The eruption continued to impact residents. The National Disaster Risk Reduction and Management Council (NDRRMC) report issued at 0800 on 31 December stated that 14,441 people (4,420 families) were spread across 34 evacuation centers and another 6,977 people (2,192 families) were staying elsewhere. The report also stated that 34 cities were under a “state of calamity”, jobs continued to be affected, and some classes remained suspended. The Alert Level remained at 3 (on a scale of 0-5); the public was warned to stay 6 km away from the summit and pilots were warned not to fly close to the volcano.

Geological Summary. Kanlaon volcano (also spelled Canlaon) forms the highest point on the Philippine island of Negros. 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.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS), The National Disaster Risk Reduction and Management Council (NDRRMC)