Photo courtesy of Philippine News Agency (PNA).
Taal Volcano remained under close monitoring Sunday after instruments detected seven volcanic earthquakes and a tremor that continued for hours, although its alert status stayed at Level 1.
The Philippine Institute of Volcanology and Seismology said the tremor began at 7:10 p.m. Saturday and persisted through the latest monitoring period. PHIVOLCS considers volcanic tremors among the seismic signals that can occur during periods of unrest at Taal.
Seismic activity this month, however, has been substantially lower than levels recorded in late August. From Sept. 1 to 13, monitoring instruments detected 52 volcanic earthquakes and three tremor episodes, compared with 229 earthquakes and 12 tremors from Aug. 20 to 28.
Sulfur dioxide emissions have also remained relatively weak, averaging 526 metric tons per day based on measurements beginning Sept. 1. PHIVOLCS monitoring earlier this month similarly showed weak emissions from the volcano.
No volcanic smog or vog was observed during the latest monitoring, while authorities reported no upwelling of hot volcanic fluids in Taal’s Main Crater Lake.
Alert Level 1 signifies low-level unrest and does not mean that volcanic activity has completely stopped. PHIVOLCS warns that sudden steam-driven, phreatic or gas-driven explosions, volcanic earthquakes, minor ashfall and dangerous concentrations or releases of volcanic gas remain possible.
The agency continues to prohibit entry into Taal Volcano Island, which is designated as a Permanent Danger Zone, particularly the Main Crater and Daang Kastila fissures. Occupancy and boating on Taal Lake and aircraft flying close to the volcano are also discouraged under the current alert.
Taal, located in Batangas south of Metro Manila, has remained capable of producing minor eruptive activity even at Alert Level 1, underscoring why authorities continue round-the-clock monitoring despite relatively subdued seismic and gas measurements.