PHIVOLCS reported that unrest at Taal continued during 11-18 May. Low-level background tremor that had begun at 0905 on 8 April continued, along with 0-201 daily low-frequency events, 2-355 daily volcanic earthquakes, and 0-249 periods of volcanic tremor with variable durations (1-35 minutes); seismicity was the lowest during 13-14 May. Most of the earthquakes were very shallow (less than 5 km deep) beneath Taal Volcano Island (TVI) and the NE part of Taal Lake. Upwelling of hot volcanic fluids in the crater lake during most days was accompanied by steam plumes that were as tall as 300 m. On other days fumarolic plumes from vents in Main Crater rose 5-40 m. Almost-daily measurements of sulfur dioxide emissions were 2,214-3,758 tonnes/day, though a peak of 5,179 tonnes/day was recorded on 12 May and comparable to a 13 January 2020 measurement taken when the volcano was erupting. Tilt data showed a minor but abrupt inflation signal on 17 May; slow and steady inflation of the Taal region was recorded by multiple instruments after the January 2020 eruption. On 18 May PHIVOLCS noted the continuing state of elevated unrest, reminding the public that the Alert Level for Taal remained at 2 (on a scale of 0-5). PHIVOLCS strongly recommended no entry onto the island, and access to the Main Crater, Daang Kastila fissure (along the walking trail), and boating on Taal Lake was strictly prohibited.

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)