Increased activity at Kanlaon volcano, Philippines


The Philippine Institute of Volcanology and Seismology (PHIVOLCS) is advising people living near the Kanlaon volcano in Negros Island to be vigilant due to the increased volcanic activity at the volcano.

In an advisory issued Saturday night, February 13, 2021 (LT), PHIVOLCS said 28 volcanic earthquakes ranging from M0.7 to 2.2 were recorded from February 11 to 13 at a shallow depth of 10 km (6.2 miles).

In 24 hours to 00:00 UTC on February 14, Kanlaon volcano's monitoring network recorded 7 volcanic earthquakes and moderate emission of white steam-laden plumes that rose 500 m (1 640 feet) before drifting southeast and northwest.

Sulfur dioxide (SO2) emission was measured at an average of 1 130 tonnes/day on February 13, 2021 — the highest recorded this year. This follows a trend since June 2020 of emissions higher than background levels of 300 tonnes/day.

Ground deformation data from continuous GPS and electronic tilt measurements have been recording slight inflation of the lower and middle slopes since June 2020.

These parameters may indicate hydrothermal or magmatic processes occurring deep beneath the edifice, PHIVOLCS said.


"Mt. Kanlaon is at alert level 1 (abnormal), but because of the increased volcanic earthquake activity in the past three days, increased gas emission on Saturday, and continued slight inflation of the volcano slopes, we issued an advisory as it is more restive now than in the past week," PHIVOLCS director Renato Solidum Jr. told the Philippine News Agency.

Solidum added that this indicates an increased possibility of phreatic eruptions (steam-driven explosion).

"Because of this, the public was reminded to be vigilant," Solidum said.

The local government units and the public are strongly reminded that entry into the 4 km (2.5 miles) radius Permanent Danger Zone (PDZ) must be strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions.

Pilots are advised to avoid flying close to the volcano’s summit as ejecta from any sudden phreatic eruption can be hazardous to aircraft. 

Kanlaon volcano on January 29, 2021. Credit: Copernicus EU/Sentinel-2, TW

Geological summary

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 (7 989 feet) 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 (20.5 miles) to the SW from Kanlaon. The summit of Kanlaon contains a 2-km-wide (1.2 miles), 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. (GVP)

Featured image credit: Copernicus EU/Sentinel-2, TW

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