TAAL VOLCANO BULLETIN (26 January 2020 8:00 AM)
This serves as a notice for the lowering of Taal Volcano’s status from Alert Level 4 (hazardous eruption imminent) to Alert Level 3 (decreased tendency towards hazardous eruption).
Taal Volcano’s condition in the two weeks following the 12-13 January 2020 phreatomagmatic eruption (main eruptive phase) has generally declined into less frequent volcanic earthquake activity, decelerated ground deformation of the Taal Caldera and Taal Volcano Island (TVI) edifices and weak steam/gas emissions at the Main Crater. These observations are supported by the following monitoring parameters:
- Significant earthquakes recorded by the Philippine Seismic Network (PSN) across the Taal region declined from 959 to 27 events/day and peak magnitudes of M4.1 to M2.1 between 12 and 24 January. The Taal Volcano Network (TVN) likewise recorded a downtrend in volcanic earthquakes from 944 to 420 events/day between 17 and 24 January with a corresponding decline in the daily total seismic energy released. In particular, hybrid earthquakes that tracked post-eruptive recharge from Taal’s deep magma reservoir to a shallow magma region beneath TVI ceased on 21 January, while the number and energy of low frequency events associated with activity in the shallow magma region diminished.
- Global Positioning System (GPS) data recorded ground deformation after the main eruptive phase that included sudden widening of Taal Caldera by ~1 meter, uplift of its northwestern sector by ~20 centimeters and subsidence of the southwestern part of TVI by ~1 meter. These patterns were followed at much smaller rates between 15 and 22 January 2020 and were generally supported by field observations of lakewater recession by ~30 centimeters around Taal Lake as of yesterday. Field observations also measured a ~2.5 m lakewater recession along the southwestern lakeshore denoting uplift of portions of the Pansipit River Valley where fissuring has been reported. The overall pattern of ground deformation is for most part supported by InSAR (satellite) data and yields a net inflation of western Taal Volcano as a consequence of magma intrusion to the shallow magma region until 21 January.
- After the main eruptive phase, activity in the Taal Main Crater diminished to infrequent weak ash eruptions and longer episodes of degassing or steaming that generated steam-laden plumes <1000 meters tall. This marked decline coupled with volcanic earthquake activity suggests stalling, degassing and reduction in gas pressures of eruptible magma in the shallow magmatic region that feeds surface eruptive activity.Sulfur dioxide or SO2 flux based on campaign Flyspec data fluctuated between a high of ~5,300 tonnes/day on 13 January to a low of ~140 tonnes/day on 22 January but has steadied at an average of 250 tonnes/day in the last five days. This low concentration average is consistent with a progressively degassed shallow magma source and diminished plume activity.
In view of the above observations, DOST-PHIVOLCS is lowering the alert status of Taal Volcano from Alert Level 4 to Alert Level 3 to reflect the overall decrease in the level of monitoring parameters. Alert Level 3 means that there is a decreased tendency towards hazardous explosive eruption but should not be interpreted that unrest has ceased or that the threat of a hazardous eruption has disappeared. Should an uptrend or pronounced change in monitored parameters forewarn a potential hazardous explosive eruption, the Alert Level may be raised back to Alert Level 4. People residing within areas at high risk to base surges who have returned after the Alert Level was stepped down must thus be prepared for a quick and organized evacuation at such time. Conversely, should there be a persistent downtrend in monitored parameters after a sufficient observation period, the Alert Level will be further lowered to Alert Level 2.
DOST-PHIVOLCS reminds the public that at Alert Level 3, sudden steam-driven and even weak phreatomagmatic explosions, volcanic earthquakes, ashfall and lethal volcanic gas expulsions can occur and threaten areas within TVI and nearby lakeshores. DOST-PHIVOLCS recommends that entry into TVI, Taal’s Permanent Danger Zone, as well as into areas over Taal Lake and communities west of TVI within a seven (7) kilometer-radius from the Main Crater must be strictly prohibited. Local government units are advised to assess areas outside the seven-kilometer radius for damages and road accessibilities and to strengthen preparedness, contingency and communication measures in case of renewed unrest. People are also advised to observe precautions due to ground displacement across fissures, frequent ashfall and minor earthquakes. Communities beside active river channels particularly where ash from the main eruption phase has been thickly deposited should increase vigilance when there is heavy and prolonged rainfall since the ash can be washed away and form lahars along the channels. Civil aviation authorities must advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircrafts.
Read more: TAAL VOLCANO ERUPTION