PHIVOLCS reported that a deformation survey of Taal conducted in December 2010 showed slight inflation as compared to a survey conducted in September 2010. Field observations on 10 January revealed no significant changes. Weak steaming from a thermal area inside the main crater was noted and the lake temperature and color were normal. During 15-16 January 10 volcanic earthquakes were detected; two earthquakes were felt by residents in barangay (neighborhood) Pira-piraso, on the N side of the island. On 17 January three volcanic earthquakes were detected and on 18 January only one was reported. The Alert Level remained at 1 (on a scale of 0-5).

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)