MANILA, Philippines – State volcanologists spotted steam coming out of fissure vents along the Daang Kastila Trail of the restive Taal Volcano.

In a bulletin on Friday morning, February 7, the Philippine Institute of Volcanology and Seismology (Phivolcs) said “weak steaming from fissure vents” along Daang Kastila is ongoing.

The trail had been used by tourists to get a glimpse of Taal’s main crater from a view deck.

But it is now extremely dangerous and potentially deadly to be there, as pointed out by Phivolcs after a video of a man along the trail went viral late January.

Phivolcs also said on Friday that it observed “moderate emission of white to dirty white steam-laden plumes rising 200 to 300 meters high” from Taal’s main crater in the past 24 hours.

These are higher than the plumes during the previous 24-hour period, which were only 50 to 100 meters high. But 200 to 300 meters is still a relatively low range.

As for the emission of sulfur dioxide (SO2), it was again “below instrumental detection due to weak plume activity” for the second straight day.

SO2 is a major gas component of magma. When magma is relatively near the surface of a volcano, SO2 is emitted.

Volcanic earthquakes are also an indicator of the movement of magma.

In the past 24 hours, the Taal Volcano Network recorded 118 volcanic earthquakes, including 5 low-frequency events and a harmonic tremor that lasted less than 3 minutes.

Low-frequency events are “caused by cracks resonating as magma and gases move toward the surface,” according to the United States Geological Survey (USGS).

Harmonic tremors, meanwhile, are volcanic earthquakes where the shaking is prolonged. USGS said they “often precede or accompany volcanic eruptions.”

The latest 24-hour total of 118 volcanic earthquakes is lower than the 132 recorded in the previous 24-hour period.

The lone harmonic tremor is also lower, as there were 11 in the previous period. Since January 30, Phivolcs has recorded 33 harmonic tremors.

“These earthquakes signify magmatic activity beneath the Taal edifice that could lead to eruptive activity at the main crater,” Phivolcs reiterated on Friday.

The Taal unrest started on January 12, the day when Alert Levels 2, 3, and 4 were raised in a matter of hours. The volcano was eventually downgraded from Alert Level 4 to Alert Level 3 on January 26, and remains at that level to date.

The highest category is Alert Level 5, which would be raised if a hazardous eruption occurs. (READ: FAST FACTS: Taal Volcano alert levels)

At present, these could occur:

• sudden steam-driven and even weak phreatomagmatic explosions
• volcanic earthquakes
• ashfall
• lethal volcanic gas expulsions

Areas in Batangas within a 7-kilometer radius from Taal’s main crater are still off-limits. These are:

• Taal Volcano Island
• barangays of Bilibinwang, Subic Ilaya, and Banyaga in Agoncillo
• barangays of Gulod, Buso-Buso, and Bugaan East in Laurel

There have been 133,696 families or 501,908 persons affected as of Friday, according to the National Disaster Risk Reduction and Management Council (NDRRMC). They are in Batangas, Quezon, Laguna, and Cavite.

There are 6,206 families or 21,732 persons still staying in evacuation centers.

When a 14-kilometer-radius danger zone was enforced during Alert Level 4, there were as many as over 38,000 families in evacuation centers. – Rappler.com