On 8 June, PHIVOLCS raised the Alert Level for Taal to 2 (scale is 0-5, 0 referring to No Alert status) due to changes in several monitored parameters, starting in late April. Since 26 April the number of earthquakes per day continued to increase, as well as the magnitude. Low-frequency volcanic earthquakes were detected on 2 June, and during the previous day high-frequency earthquakes were noted. In addition to increased seismicity, the temperature of the Main Crater Lake increased from 32 degrees Celsius on 11 May to 34 degrees Celsius on 24 May. Steaming from the N and NE sides of Main Crater occasionally intensified. Deformation data had shown slight inflation since 2004; measurements taken at the SE side of Taal on 7 June showed further inflation by 3 mm.

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)