DECEPTIVELY CALM The Taal Volcano Island, locally known as “Pulo,” is deceptively calm in this photo taken on Oct. 2 from a viewpoint in Tagaytay City amid its ongoing unrest, which has prompted state volcanologists to warn officials of towns and cities around Taal Lake to prepare for possible escalation of its alert level from 1 to 2. —SHERWIN TAN
LUCENA CITY — Two phreatic or steam-driven eruptions and eight volcanic earthquakes were recorded in Taal Volcano in Batangas province over the last 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Tuesday morning, Oct. 8.
In its bulletin, the Phivolcs said the eruption on Monday only lasted from one to four minutes.
The earthquakes were accompanied by one volcanic tremor that lasted two minutes long, the state volcanologists said.
Phivolcs defines volcanic earthquakes as those “generated by magmatic processes or magma-related processes beneath or near an active volcano.”
Volcanic tremors, on the other hand, are “continuous seismic signals with regular or irregular oscillations and low frequencies (typically 0.5–5 Hz) that can last for more than a minute.”
Taal Volcano has been showing signs of unrest since last week.
On Sunday, Oct. 6, the volcano logged a one-minute phreatic eruption.
On Saturday, the volcano had six minor phreatic eruptions lasting from one to three minutes; a four-minute minor phreatomagmatic eruption; and nine volcanic earthquakes, including two tremors that lasted six minutes.
On Oct. 2, the volcano had another phreatomagmatic eruption that lasted 11 minutes.
The phreatomagmatic event, according to Phivolcs, was “likely driven by sudden contact of water with a small branch of shallow magma that has been in place beneath the Taal main crater and that has been degassing sustained levels of SO2 (sulfur dioxide) for the past three years.”
The state volcanologists define phreatic eruption as a “steam-driven explosion that occurs when water beneath the ground or on the surface is heated by magma, lava, hot rocks, or new volcanic deposits (for example, tephra and pyroclastic-flow deposits).”
However, the unrest is unlikely to progress into a magmatic eruption based on the background levels of volcanic earthquake activity and the detected ground deformation, Phivolcs emphasized.
As of Friday, Oct. 4, 30 “minor eruptive events” had been recorded since Sept. 22, Phivolcs said.
The eruptions have prompted state volcanologists to warn officials of towns and cities around Taal Lake to prepare for possible escalation of its alert level from 1 to 2.
Phivolcs warned that Alert Level 2 may be raised if Taal’s phreatomagmatic activity persists or intensifies.
Taal’s current Alert Level 1 status means “it is still in abnormal condition and should not be interpreted to have ceased unrest nor ceased the threat of eruptive activity,” Phivolcs said.
Alert Level 2 means “probable intrusion of magma at depth, which can lead to magmatic eruption,” the agency said.
With the ongoing unrest of the volcano, the Regional Disaster Risk Reduction and Management Council in Calabarzon in a memorandum on Oct. 2 reiterated that Taal Volcano Island in the middle of the lake remains a “no-human-settlement area.”
The Office of Civil Defense Region IV-A is on blue alert after the phreatomagmatic eruption on Oct. 2, meaning half of the staff of government agencies involved in disaster preparation would be on standby for emergencies.
In its latest update, Phivolcs recorded the emission of 2,068 metric tons of SO2 from Taal’s main crater, which rose 900 meters above Taal Volcano Island which sits in the middle of Taal Lake.
The Phivolcs classified the latest spewing activity of the volcano as “moderate emission.”
However, there was no volcanic smog, or “vog,” during the latest observation period.