Report on Taal (Philippines) — 22 January-28 January 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 January-28 January 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Taal (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 January-28 January 2020. 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 white steam-laden plumes rose as high as 800 m above Taal’s main vent during 22-28 January and drifted SW and NE; ash emissions ceased around 0500 on 22 January. Remobilized ash drifted SW on 22 January due to strong low winds, affecting the towns of Lemery (16 km SW) and Agoncillo, and rose as high as 5.8 km (19,000 ft) a.s.l. as reported by pilots.
PHIVOLCS stated that since the 12-13 January phreatomagmatic eruption activity has generally weakened. Both the number and magnitude of volcanic earthquakes declined; by 21 January hybrid earthquakes had ceased and both the number and magnitude of low-frequency events had diminished. GPS data had recorded a sudden widening of Taal Caldera by ~1 m, uplift of the NW sector by ~20 cm, and subsidence of the SW part of Volcano Island by ~1 m just after the main eruption phase. The rate of the deformation patterns was smaller during 15-22 January, and generally corroborated by field observations; Taal Lake had receded about 30 cm by 25 January but about 2.5 m of lakewater recession (due to uplift) was observed around the SW portion of the lake, near the Pansipit River Valley where ground cracking had been reported. The Alert Level was lowered to 3 (on a scale of 0-5) on 26 January and PHIVOLCS recommended no entry onto Volcano Island and Taal Lake, nor into towns W of the island within a 7-km radius. Sulfur dioxide emissions were low at 140 tonnes per day on 22 January but averaged around 250 tonnes per day through 26 January; emissions were 87 tonnes per day on 27 January and below detectable limits the next day. According to the Disaster Response Operations Monitoring and Information Center (DROMIC) there were a total of 125,178 people in 497 evacuation centers as of 2020 on 28 January.
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.