No more trace of sulfur dioxide but low-frequency quakes continue in Taal

There had been no more trace of sulfur dioxide released by Taal Volcano, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Tuesday.

"Sulfur dioxide emission was below instrumental detection," PHIVOLCS said in a bulletin released at 8 a.m.

Volcanologists are using the measurements of sulfur dioxide emission as a parameter to assess the movement of magma towards the surface.

Meanwhile, the Taal Volcano Network recorded 92 volcanic earthquakes in the past 24 hours—four of which were low-frequency ones.

According to the United States Geological Survey, low-frequency earthquakes are "caused by cracks resonating as magma and gases move toward the surface."

"They are often seen prior to volcanic eruptions, but their occurrence is also part of the normal background seismicity at some volcanoes and their occurrence does not necessarily indicate that an eruption is imminent," the USGS said. 

The Philippine Seismic Network, on the other hand, plotted three new volcanic earthquakes with no felt event since 5 a.m. on Monday to 5 a.m. on Tuesday.

The total number of plotted volcanic earthquakes since Taal Volcano's unrest on January 12 is now 755.

"These earthquakes signify magmatic activity beneath the Taal edifice that could lead to eruptive activity at the Main Crater," PHIVOLCS said.

Alert Level 3 remains over Taal Volcano and PHIVOLCS warns the public that "sudden steam-driven and even weak phreatomagmatic explosions (involving both magma and water), volcanic earthquakes, ashfall, and lethal volcanic gas expulsions can still occur and threaten areas within Taal Volcano Island and nearby lakeshores."

Weak to voluminous emission of white to dirty white steam-laden plumes, 100 to 800 meters tall, was observed in Taal Volcano's main crater in the past 24 hours. These plumes drifted southwest.

PHIVOLCS advised that the Taal Volcano Island and communities west of it within a seven-kilometer radius from the main crater should remain off-limits.

Areas outside the seven-kilometer radius have to be assessed by authorities for damage and road accessibility. Returning residents must also be prepared to evacuate in case of the volcano's renewed unrest, it added.

Further, those living beside active river channels with thick deposits of volcanic ash from Taal's previous eruption must be vigilant for possible lahars when there is heavy and prolonged rainfall.

Aircraft must also avoid flying close to the volcano due to hazards that may be posed by airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash, PHIVOLCS said. —KBK, GMA News