PHIVOLCS reported continuing unrest at Taal during 18-25 October. Daily white steam emissions rose as high as 3 km above the lake and drifted NE, NW, and SW. Upwelling gasses and hot fluids in the lake were periodically visible. Sulfur dioxide emissions averaged 6,702 tonnes per day on 20 October. The seismic network recorded 0-6 daily volcanic earthquakes and a few periods of volcanic tremor during 20-23 October. Webcam images showed increased activity during 21-22 October with 29 small phreatomagmatic bursts from a vent on the NE part of the lake, each lasting 1-5 minutes long. Some of the events produced 200-m-tall steam-rich plumes and very, short, dark ash plumes that immediately collapsed back into the water. Not all events generated detectable signals in the seismic and infrasound records. Ash plumes rose to 600 m (2,000 ft) a.s.l. on 21 October and drifted W according to the Tokyo VAAC. Two small phreatomagmatic bursts, each lasting 6-7 minutes long were recorded during 22-23 October. Sulfur dioxide emissions averaged 1,403 tonnes per day on 24 October. Ground deformation measurements continued to show slight inflation in the western half of the caldera and deflation in the eastern half. The Alert Level remained at 1 (on a scale of 0-5), and PHIVOLCS reminded the public that the entire Taal Volcano Island was a Permanent Danger Zone (PDZ).

Geological Summary. Taal is one of the most active volcanoes in the Philippines and has produced some powerful eruptions. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, with several submerged eruptive centers. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)