The Philippine Institute of Volcanology and Seismology issued a notice of increased seismic activity at Kanlaon Volcano on Election Day, May 12.
Phivolcs said 72 volcanic earthquakes were recorded by the Kanlaon Volcano Network between 12 a.m. and 12 p.m. Monday.
These events ranged in strength between ML0.3 and ML3.1 and were generated at 0 to 8 kilometers depths beneath the northern and northwestern flanks of the volcanic edifice, Phivolcs said.
A total of 135 volcanic earthquakes had been recorded since 12 a.m. on Sunday, May 11, it added,
These included relatively strong volcano-tectonic or VT earthquakes.
VTs are generated by rock fracturing processes and the increase in VT activity strongly indicates progressive rock-fracturing beneath the volcano as rising magma or magmatic gas drives a path towards the surface, the Phivolcs notice said
Volcanic sulfur dioxide (SO2) gas emissions from the summit crater of Kanlaon, averaged 554 tons on Sunday, it added.
There has been a decline in the average sulfur dioxide emission from 4,144 since June 2 to 2,114 since 1 April 1, Phivolcs said.
These parameters indicate that the blockage of volcanic gas emission (or closed-system degassing) may result in pressurization and swelling of the edifice potentially leading to moderately explosive eruption at Kanlaon.
Alert Level 3 (magmatic unrest) prevails over Kanlaon, which means that the volcano is in a state of magmatic unrest, and currently there are increased chances of short-lived moderately explosive eruptions occurring that could generate life-threatening volcanic hazards, Phivolcs said.
It is recommended that communities within a 6-km radius from the summit crater remain evacuated due to the danger of pyroclastic density currents or PDCs, ballistic projectiles, ashfall, rockfall and other related hazards, it said.
Local government units must continue to prepare their communities within the PDC hazard zone for subsequent evacuation in case unrest further escalates and hazardous worst-case explosive eruption becomes imminent, Phivolcs said.
Increased vigilance against potential syn-eruption lahars and sediment-laden stream flows in channels draining the edifice is strongly advised should intense rains occur during eruptive unrest, it added.,
Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft, Phivolcs said.*