By Ellalyn De Vera-Ruiz
Taal Volcano remains under Alert Level 1 amid the high number of volcanic activity-triggered earthquakes that have been occurring since March this year.
Science and Technology Undersecretary and Philippine Institute of Volcanology and Seismology (Phivolcs) Director Renato Solidum said Alert Level 1 will be maintained “in the meantime.”
Based on the 24-hour monitoring of the Taal Volcano’s seismic network, 57 volcanic earthquakes were observed from Monday morning to Tuesday morning.
One of the events, which occurred at 9:59 a.m. last Monday, was felt at Intensity I, while rumbling sound was heard by residents in Brgy. Alas-as, San Nicolas, Batangas.
Phivolcs also observed that field measurements last November 7 at the volcano’s main crater lake yielded a decrease in water temperature from 33.0 degrees Celsius (°C) to 32.8 °C, an increase in water level from 0.46 meters to 0.49 meters and an increase in acidity from a pH of 2.93 to 2.85.
Ground deformation measurements through precise leveling surveys from September 19-26 indicated inflation of the edifice consistent with recent results from continuous global positioning system (GPS) data.
Solidum explained that the number of volcanic earthquakes that occurred in Taal Volcano remains high since Alert Level 1 was raised last March 28.
Some earthquakes were felt with intensity ranging from Intensity I (scarcely perceptible) to Intensity III (weak shaking) in the towns of Balete, Talisay, Agoncillo, and San Nicolas, Batangas.
“Often, these felt earthquakes are accompanied by rumbling sounds,” he said.
He also noted that an increase in carbon dioxide is also “observed inside the main crater starting around April of 2019.”
“Moreover, the edifice of Taal Volcano is inflating based on data from GPS and results from precise leveling survey,” he added.
Solidum pointed out that Alert Level 2 will be raised if these signs continue or are frequently observed from Taal Volcano: increasing number of volcanic earthquakes, higher concentration of carbon dioxide and other gases, inflation of the volcano’s edifice, increased water temperature and/or ground probe hole temperatures, and occurrence of widespread bubbling at the lake of the main crater.
For now, Alert Level 1 remains in effect over Taal Volcano.
While “hazardous eruption is not imminent,” Phivolcs still reminded the public that the main crater should be strictly off-limits because sudden steam explosions can occur and high concentrations of toxic volcanic gases can be released.
The northern portion of the main crater rim, in the vicinity of Daang Kastila Trail, can also become hazardous when steam emission along existing fissures suddenly increases.
Furthermore, the public is reminded that the entire volcano island is a permanent danger zone and permanent settlement is strictly prohibited.
Taal Volcano had a total of 33 historical eruptions and the last major eruption happened on October 3, 1977.