Kanlaon Volcano, which underwent a “moderately explosive eruption” early last Tuesday morning, likely erupted due to a blockage in the volcanic gas pathways.

"Our interpretation is that the pathway where volcanic gas is released has become blocked. This is because the gas sublimates minerals along its passage, which can cause a buildup and blockage. As a result, the volcanic gas may break through new pathways, which could potentially trigger an eruption,” said Maria Antonia Bornas, chief of the Volcano Monitoring and Eruption Prediction Division of Phivolcs.

She added that Kanlaon’s volcanic ash emission was recorded at less than 1,000 tonnes per day, which is below the volcano’s average output.

"When pressurization breaks, that’s when an eruption occurs," Bornas added, clarifying that no lava emission was detected at the volcano, as seen through the agency’s thermal cameras.

At around 2:55 a.m. last Tuesday, Kanlaon Volcano erupted for five minutes, generating a grayish, voluminous plume that rose 4.5 kilometers from the vent. The eruption caused light ashfall in barangays within La Castellana, La Carlota City, and Bago City.

Regarding Bulusan Volcano, Bornas said that while it previously recorded at least a hundred volcanic earthquakes in its vicinity, the activity has decreased over the past few days.

Phivolcs issued an advisory last Monday after observing increased activity in Bulusan Volcano, which had logged at least 300 volcanic earthquakes.

In addition to the decrease in volcanic earthquakes, state seismologists reported that Bulusan’s sulfur dioxide emissions are nearing background levels.

"Background level is the monitoring parameter which usually registers in the volcano even if they are in a quiet sense," Bornas clarified.

Bulusan Volcano remains under Alert Level 1, while Kanlaon Volcano is under Alert Level 3, indicating that a hazardous eruption could occur within weeks.