Report on Taal (Philippines) — 29 June-5 July 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 June-5 July 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Taal (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 June-5 July 2011. Smithsonian Institution and US Geological Survey.
14.002°N, 120.993°E; summit elev. 311 m
All times are local (unless otherwise noted)
PHIVOLCS reported that during the previous 11 weeks, since the Alert Level for Taal was raised to 2 (on a scale of 0-5) on 9 April, the number of earthquakes recorded daily gradually declined, hydrothermal activity abated, carbon dioxide gas emissions decreased, ground temperature and total magnetic field measurements in the main crater showed no significant changes, and deformation data showed no signs of increasing pressure. On 5 July the Alert Level was lowered from 2 to 1.
Geologic Background. Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. 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, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.