Taal Volcano. (File photo)

MANILA – A high volcanic sulfur dioxide (SO₂) emission reaching 13,572 tons was observed over the Taal Volcano on Thursday, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported Friday.

This has produced "significant volcanic smog" or vog over the Taal Caldera, and the volcanic gas is expected to drift east to north-northeast of the Taal Volcano Island (TVI).

In an advisory on Friday, Phivolcs said vog was observed to thicken between 9 a.m. and 2 p.m. Thursday. Sulfurous stench was reported by residents of Banyaga, Agoncillo; Poblacion 5, Buso-buso, and Gulod in Laurel; and Poblacion 1 in Talisay, Batangas.

"Since the beginning of August 2022, there has been an increase in degassing activity in the form of visible upwelling of volcanic fluids in the Main Crater Lake, and emission of voluminous steam-rich plumes that last night rose 2,800 meters above TVI," the advisory read.

Vog consists of fine droplets containing volcanic gas which is acidic and can cause irritation of the eyes, throat, and respiratory tract in severities, depending on the gas concentrations and durations of exposure.

People who may be particularly sensitive to vog are those with asthma, lung disease and heart disease, the elderly, pregnant women, and children.

Phivolcs advised communities that may be affected by vog to avoid outdoor activities to limit their exposure; as well as to keep their doors and windows closed.

It also urged residents to wear a mask (ideally an N95) and to drink plenty of water to reduce throat irritation.

Meanwhile, for the past 24 hours, five shallow volcanic tremors 3 to 8 minutes in duration were recorded. These tremors signify fluid or gas movement.

Phivolcs added that crop damage that likely resulted from acid rain was reported in Cabuyao, Laguna this month.

Taal Volcano is still under Alert Level 1 (low-level unrest), which means sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall, and expulsions of volcanic gas could threaten areas within Taal's permanent danger zone.

Entry into the TVI, especially the vicinities of the Main Crater and the Daang Kastila fissure, must remain strictly prohibited, according to Phivolcs.

Local government units are also urged to continuously assess previously evacuated barangays around Taal Lake for damage and road accessibilities, and to strengthen preparedness, contingency and communication measures in case of renewed unrest. (PNA)