Rising trend of SO2 emission at Taal volcano, Philippines


The first measurement of volcanic sulfur dioxide or SO2 flux from the Taal Main Crater on August 19, 2021, totaled 15 347 tonnes/day. This marks a rising trend in volcanic SO2 degassing since August 13, with the short-term average from then until present measured at 8 351 tonnes/day, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said in an advisory issued August 19.

In the same period, tall steam-rich plumes that rose 1 – 3 km (3 280 – 9 840 feet) were also generated by the Taal Main Crater.1

Atmospheric conditions of air temperatures at 32.2 ºC (90 ºF), relative humidity at 55.8% and wind velocities at 0 to 2.3 meters/second within the lower 3 km (1.8 miles) of the atmosphere prevailed over Taal Caldera today.

The high SO2 flux, water vapor emitted in plumes, weak air movement, and solar radiation will continue to produce volcanic smog or vog over the Taal region.

Reports of adverse effects on some residents of Talisay and Brgy. Barigon, Agoncillo have been received, PHIVOLCS said. Hazy conditions were also observed over Taal Lake and municipalities surrounding Taal Lake.

In 24 hours to 00:00 UTC on August 20, the Taal Volcano Network recorded 64 volcanic earthquakes, including 50 volcanic tremor events having durations of 2 to 24 minutes, 14 low-frequency volcanic earthquakes, and low-level background tremor that has persisted since July 7, 2021.2

Based on ground deformation parameters from electronic tilt, continuous GPS, and InSAR monitoring, Taal Volcano Island has begun deflating in April 2021 while the Taal region continues to undergo very slow extension since 2020.

"As a reminder, vog consists of fine droplets containing volcanic gas such as SO2 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 particularly sensitive to such ill effects are those with health conditions such as asthma, lung disease and heart disease, the elderly, pregnant women, and children," PHIVOLCS said.

If vog occurs and exposure cannot be avoided, please be mindful of the following:

  1. Limit your exposure. Avoid outdoor activities, stay indoors, and shut doors and windows to block out vog.
  2. Protect yourself. Cover nose, ideally with an N95 facemask. Drink plenty of water to reduce any throat irritation or constriction. If belonging to the particularly sensitive group of people above, watch over yourself and seek help from a doctor or the barangay health unit if needed. If serious effects are experienced, call the doctor or the barangay health unit.

"The public is reminded that Alert Level 2 (Increased Unrest) prevails over Taal Volcano and that the threat of sudden steam- or gas-driven explosions and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within and around TVI.

"Increasing SO2 flux may also forewarn potential phreatomagmatic activity similar to the July 1, 2021 eruption. Venturing into TVI must therefore remain strictly prohibited, and LGUs are advised to continually check on the preparedness of their constituent communities."


1 TAAL VOLCANO ADVISORY – August 19, 2021 – 16:30 LT – PHIVOLCS


Featured image: Taal volcano on August 5, 2021. Credit: Copernicus EU/Sentinel-2, TW

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