Taal sulfur dioxide, volcanic earthquakes go down further
MANILA, Philippines – Taal Volcano's sulfur dioxide (SO2) emission and number of volcanic earthquakes went down further in the past 24 hours, said state volcanologists on Tuesday morning, January 28.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said in its 8 am bulletin on Tuesday that the SO2 emission was "below instrumental detection," or too low to be detected.
SO2 is a major gas component of magma. More SO2 is released when magma is near the surface of a volcano.
The previous average given on Monday, January 27, was 87 tons per day.
At high points in Taal's activity in the past two weeks, SO2 emission averaged thousands of tons per day.
Meanwhile, there continues to be fewer volcanic earthquakes. Quakes are another indicator that magma is moving or rising toward the surface.
The Philippine Seismic Network has plotted 755 volcanic earthquakes since 1 pm of January 12, when the Taal unrest began. Of these, 176 were magnitudes 1.2 to 4.1 and were felt at Intensities I to V.
But from 5 am on Monday until 5 am on Tuesday, there were only 3 volcanic earthquakes plotted. These were magnitudes 1.5 to 2.2, with no felt event.
The Taal Volcano Network, which can record small earthquakes undetectable by the Philippine Seismic Network, recorded 92 volcanic earthquakes in the past 24 hours.
These included 4 low-frequency events, which are "caused by cracks resonating as magma and gases move toward the surface," according to the United States Geological Survey.
Phivolcs had said on Monday that the Taal Volcano Network recorded 170 volcanic earthquakes, including 4 which were low-frequency.
As for activity at the main crater, Phivolcs said on Tuesday morning that it observed "weak to voluminous emission of white to dirty white steam-laden plumes 100 to 800 meters" in the past 24 hours.
Despite the easing situation, Phivolcs reiterated that Alert Level 3 remains raised for Taal Volcano, since the unrest has not completely stopped.
The following could still happen, which would threaten Taal Volcano Island and lakeshore areas in the province of Batangas:
- sudden steam-driven and even weak phreatomagmatic explosions
- volcanic earthquakes
- lethal volcanic gas expulsions
These areas are within a 7-kilometer radius from the main crater, which is Phivolcs' recommended danger zone while Taal is under Alert Level 3.
The volcano had been downgraded from Alert Level 4 to Alert Level 3 or a "decreased tendency towards hazardous eruption" last Sunday, January 26.
Alert Level 4, which meant a hazardous eruption might occur within hours to days, was raised on January 12, forcing tens of thousands of families to flee. (READ: Taal Volcano evacuees appeal: 'We need cash aid') – Rappler.com