LEGAZPI CITY, Albay—Volcanic quakes, sustained inflation of the edifice, gas emissions and crater glows are very signs of a coming eruption of Mayon volcano and people at its foot should never trust its momentary lull, warned Philippine Institute of Volcanology and Seismology (Phivolcs) director Renato Solidum Monday.

The Phivolcs has already installed two units of digital tilt meters along Mayon volcano, particularly in the village of Anoling in Camalig and at the Mayon Resthouse in Tabaco City, both within the six-kilometer permanent danger zone, Solidum said.

A tilt meter is used in measuring ground deflation on the slopes of Mayon.

“As much as the scientists are keeping their eyes and ears on Mayon, no one should trust it on a daily basis of its manifestations but instead be very careful because the sustained threat is still there although we also refer to its 2006 eruption event (a protracted one),” he added.

Solidum explained that if magma was fast moving upwards towards the crater, it would explode violently like what happened in 1814 when the old Cagsawa town was buried in mud, rendering the area in ruins and another eruption recorded in 1897 with several thousands killed.

“Now, the rise and fall in the gas emission and earthquake rates indicate that Mayon is degassing and has time to release pressure and would wait for another fresh batch of magma push upwards, that is why there are changes in the rates of the monitored parameters,” he explained.

Solidum, however, warned that scientists could not say when or what kind of eruption (violent or not) but disaster authorities must maintain the warning against venturing at the six-kilometer permanent danger zone and the seven-km extended danger zone, especially at the southeast quadrant facing Daraga and Santo Domingo towns and this city.

“There is a need for a strong collaboration among local disaster councils to maintain the safety of the people and consistently attain a zero-casualty rate even in the event of its eruption,” he advised.

Mayon’s trend of volcanic quakes showed a descending pattern in the past few days: 35 volcanic earthquakes from Friday to Saturday; 23 from Saturday to Sunday; and five from Sunday to Monday.

As earlier warned by resident volcanologist Eduardo Laguerta, the continuous tremors might indicate a coming eruption.

Friday’s bulletin revealed that harmonic tremors continued from Thursday to Friday, but not after that, Laguerta said.

Once Mayon showed tremors, it indicates a coming eruption, he said.