Sulfur dioxide emissions down, number of volcanic quakes up in Taal

More than a month after Taal Volcano's initial eruption, Alert Level 3 remains as the parameters being used to assess its activity continue to rise and fall in previous days.

According to the bulletin released by PHIVOLCS on Tuesday, the volcano's sulfur dioxide emission was down to an average of 105 tonnes per day when measured on February 10.

It was slightly lower than the previous average of 116 tonnes per day on February 8.

The presence of sulfur dioxide in the atmosphere indicates the upward movement of magma to the surface, according to state volcanologists.

During the height of Taal Volcano's unrest, its sulfur dioxide emissions reached more than 5,000 tonnes/day.

Meanwhile, 87 volcanic earthquakes including one low frequency event and two harmonic tremors having durations of one to three minutes were detected by the Taal Volcano Network in the past 24 hours.

Low-frequency earthquakes are "caused by cracks resonating as magma and gases move toward the surface" while harmonic tremors are continuous rhythmic earthquakes that "often precede or accompany volcanic eruptions," according to the United States Geological Survey.

PHIVOLCS said that the earthquakes "signify magmatic activity beneath the Taal edifice that could lead to eruptive activity at the main crater."

In the past 24 hours, the main crater weakly emitted steam-laden plumes which rose 50 to 100 meters high before drifting southwest.

PHIVOLCS warned 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."

It advised that the Taal Volcano Island and communities west of the island 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 damages and road accessibilities. 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