Report on Taal (Philippines) — 10 February-16 February 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 February-16 February 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Taal (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 February-16 February 2021. 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 geochemical data collected from Taal’s Main Crater lake indicated a continuous acidification of the water from pH 2.79 to 1.59 between January 2020 and February 2021. A maximum temperature of 77.1 degrees Celsius was unseasonably high, and carbon dioxide/hydrogen sulfide gas flux ratios were consistent with shallow magma degassing. Tilt data indicated minor deflation around Main Crater, though minor inflation was consistently recorded across the Taal region as indicated by analysis of GPS data, InSAR, and microgravity changes.
A total of 68 relatively weak tremor signals were detected during 13-15 February; 50 of those were recorded during 0500-1500 on 15 February. The events on 15 February ranged in duration from two to five minutes and occurred at depths less than 1 km. The depth and location of the earthquakes suggested increased hydrothermal activity beneath Taal Volcano Island. Increased seismic activity continued through 16 February; from 0800 on 15 February to 0800 on 16 February there were a total of 98 earthquakes. The Alert Level remained at 1 (on a scale of 0-5) and PHIVOLCS strongly recommended no entry onto the island, and the Main Crater and the Daang Kastila fissure (along the walking trail) was strictly prohibited.
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.