STATE volcanologists are closely monitoring Kanlaon Volcano on Negros island in central Philippines after it emitted white steam-laden plumes 200 meters into the sky.

At least 136 earthquakes were recorded in the volcano, part of the so-called Pacific Ring of fire — a major area in the basin of the Pacific Ocean where many earthquakes and volcanic eruptions occur — in the past 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on its website.

The volcano was at Level 1, meaning it was in an abnormal condition and had entered a period of unrest, the agency said in an 8 a.m. bulletin on Monday.

Four of the 136 earthquakes were at magnitude 3.2 to 4.7, it said.

Intensities 2 to 5 were felt in La Carlota and Bago City in Negros Occidental and Canlaon City in Negros Oriental.

Phivolcs said sulfur dioxide emission was at an average of 438 tonnes a day on June 13.

Lower and mid-slopes of Kanlaon seem to have subsided as magma leaves the volcano’s underground reservoir, it said.

The agency said lower slopes of the volcano’s southeastern flanks have been subsiding, while mid-slopes have been swelling since April.

“These parameters indicate that hydrothermal or magmatic activity is occurring beneath the edifice,” it said.

The four-kilometer radius of the permanent danger zone is off-limits to the public given the risk of sudden steam-driven eruptions, Phivolcs said.

Civil aviation authorities should advise pilots to avoid flying close to the volcano’s peak, it added. — Vann Marlo Villegas