Volcanic earthquakes at Kanlaon surge to 1 217, Philippines

The Kanlaon volcano's seismic network recorded 1 217 volcano earthquakes on December 14, 2017, an uptick from already unusually high 578 recorded on December 13.

Wispy emission of white steam-laden plumes were observed coming from the summit crater, PHIVOLCS said 08:00 PHT today (00:00 UTC). Ground deformation data from continuous GPS measurements indicate slight inflation of the edifice since December 2015.

Sulfur dioxide (SO₂) emission was measured at an average of 687 tonnes/day on December 13, 2017, the last reported measurement.

Paul Alanis, a science research specialist of Philippine Institute of Volcanology and Seismology (PHIVOLCS) central office, said that Kanlaon’s volcanic activities are not normal which is why the volcano remains on Alert Level 2. This means that the volcano is undergoing a moderate level of unrest.

There is a probable intrusion of magma at depth which may or may not lead to a magmatic eruption. However, as long as you are not in the 4-km (2.5 miles) Permanent Danger Zone (PDZ), there is nothing to worry about, Alanis said.

PHIVOLCS reminded local government units and the public that entrance into the PDZ is strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions.

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

Seismic unrest under the volcano started on August 18, 2017 and continued increasing, forcing PHIVOLCS to raise the Alert Level from 1 to 2 on Wednesday, November 15, 2017.

The last notable eruption of this volcano started at 01:47 UTC on December 9, 2017 and lasted approximately 10 minutes. The event ejected steam and dark ash but was poorly observed due to clouds covering the summit region. Rumbling sound was reportedly heard in Brgy. Manghanoy, La Castellana, and thin ash fell on Sitio Guintubdan, Brgy. Ara-al, La Carlota City.

The December 9^th eruption was preceded by a resumption of degassing at the summit crater at 22:34 UTC on December 8, which was last observed September 2016.

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: Kanlaon volcano. Credit: PHIVOLCS