(SPOT.ph) Volcanic smog (vog) hovers over the Taal Volcano on Friday, September 22, while over Mayon Volcano, Phivolcs continues to monitor activities like debris and ash flow.
As a few local government units (LGUs) observing foggy skies in Metro Manila have suspended classes citing the Taal vog, Phivolcs said the vog only affects areas on the west-southwest of the volcano, not towards the capital region.
Taal updates today, September 22, 2023: Vog, steam plumes rising
Phivolcs released a vog notice on Thursday noon, noting that vog has been forming over the Taal Region since the first week of September.
Also being monitored are steam plumes as high as 2.4 kilometers that drift west-southwestward and southwestward. It also spewed 4,568 tons of sulfur dioxide on September 21. Phivolcs tallied five volcanic tremors that lasted 20 minutes to more than nine hours.
Vog contains volcanic gas such as sulfur dioxide, and with it being acidic, it can irritate the eyes, throat, and respiratory tract depending on the concentration and duration of exposure to it.
Residents around the area are advised to cover their nose and mouth, ideally with N95 face masks, limit their exposure, avoid outdoor activities and stay indoors, and shut the doors and windows to stop the vog from coming indoors.
Acid rain is also possible during rainfall in areas affected by volcanic gas emissions and it can damage metal roofs and crops.
Taal Volcano is still under Alert Level 1 (low-level unrest), where sudden phreatic eruption or steam-driven explosions, volcanic earthquakes, minor ashfall, and possible expulsion of volcanic gas can happen.
Mayon Volcano update: Volcanic earthquakes, ash flow
Mayon Volcano recorded 15 volcanic earthquakes, over 162 rockfall events, and two pyroclastic density currents (PDC) or ash and debris flows in just the past 24 hours, Phivolcs said Friday.
Lava flows have been observed and have advanced to 3.4 kilometers in Bonga in the southeast, 2.8 kilometers in Mi-isi in the south, and 1.1 kilometers in Basud in the east.
It also emitted volcanic sulfur dioxide, averaging 868 tons daily on September 20.
Under Alert Level 3 (intensified or magmatic unrest), a hazardous eruption is still possible within weeks or days. Phivolcs has recommended that residents living near the area evacuate the six-kilometer Permanent Danger Zone (PDZ) as the volcano poses possible threats like debris, ash flow, and lahar.
Current Metro Manila air quality, according to PAGASA and DENR
PAGASA said that the current gloomy skies in Metro Manila can be explained by "very small particles getting trapped close to the surface due to the presence of a thermal inversion, high humidity, and calm wind conditions."
In addition, the Department of Natural Resources has pointed out that the primary reason for elevated air quality concerns in certain areas of Metro Manila is the significant congestion of vehicles, particularly during rush hours.
What is fog, vog, smog, and haze
Fog is characterized by water droplets or atmospheric moisture, typically appearing white.
Vog (volcanic smog), on the other hand, is a form of air pollution resulting from volcanic emissions, consisting of sulfur dioxide gas and aerosols that create visible haze. Essentially, it stems from airborne pollutants emitted by volcanoes.
Smog is air pollution that occurs when smoke and chemical fumes combine. Its severity can be exacerbated by thermal inversion, where a warm air layer traps the polluted air below, preventing its dispersion.
Haze occurs when particles such as dust and other imperceptible air pollutants interact with sunlight. This phenomenon diminishes visibility and imparts a grayish tint to the sky.