Increased activity at Taal volcano, alert level raised, Philippines

Increased activity at Taal volcano, alert level raised, Philippines

The Philippine Institute of Volcanology and Seismology has raised the alert status of Taal volcano from Alert Level 0 to Alert Level 1 (abnormal) on March 28, 2019. The last eruption of this volcano took place in 1977. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.

There has been a recent change in the condition of Taal Volcano based on the following observed changes in monitoring parameters:

  1. Volcanic Earthquake Activity: A total of 50 volcanic earthquakes have been recorded by Taal Volcano’s seismic monitoring network since March 22, 2019. This recent earthquake swarm may indicate rock-fracturing beneath the edifice possibly associated with hydrothermal activity. Prior to this, the frequency of volcanic earthquakes was on average within the baseline levels (0-5 events/day) since 2016.
  2. Ground Deformation: Cumulative elevation changes of the volcanic edifice based on precise leveling (PL) measurements this March 2019 indicate that it has slightly inflated relative to November 2018 after a period of general deflation since 2016. Slight inflation of the edifice starting in January 2019 was also recorded by continuous Global Positioning Systems (GPS) after a period of general deflation since 2016.
  1. Gas Emission: Dissolved carbon dioxide (CO2) concentrations in Taal Main Crater Lake (MCL) based on continuous measurements have been gradually increasing since February 2019, indicating a slight increase in the input of volcanic CO2 degassing from the hydrothermal system into the lake.

In view of the above, DOST-PHIVOLCS has raised the alert status of Taal from Alert Level 0 to Alert Level 1. This means that the volcano is at an abnormal condition. 

The public is reminded that the Main Crater should be strictly off-limits because sudden steam explosions can occur and high concentrations of lethal volcanic gases can be released.

The northern portion of the Main Crater rim, in the vicinity of Daang Kastila Trail, can also become hazardous when fumarolic or degassing activity along existing fissures suddenly increases.

Furthermore, the public is also reminded that the entire Volcano Island is a Permanent Danger Zone (PDZ), and permanent settlement in the island is strongly not recommended.

Taal Volcano’s seismic monitoring network recorded 3 volcanic earthquakes during the past 24 hours, PHIVOLCS reported 00:00 UTC (08:00 LT), March 29.

Field measurements on March 28, 2019 at the eastern sector of the Main Crater Lake yielded an increase in water temperature from 30.7 °C to 31.7 °C (87.2 - 89 °F), a decrease in water level from 0.46 m to 0.41 m (1.5 to 1.3 feet) and increase in acidity from pH 2.95 to pH 2.67.

Ground deformation measurements through precise leveling surveys from March 18 to 27, 2019 indicated slight inflation of the edifice consistent with recent results from continuous GPS data. 

Image credit: Ray in Manila

The last eruption of this volcano started in October 1997 and lasted approximately 1 month (VEI 2). VEI4 eruption took place from September 28 - 30, 1965. Both eruptions took place on Taal's SW flank near Mt. Tabaro.

Geological summary

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 topography of SW Luzon. The 15 x 20 km (9 x 12 feet) Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 (103 mi2) surface lies only 3 m (9.8 feet) above sea level. 

The maximum depth of the lake is 160 m (525 feet), and several eruptive centers lie submerged beneath the lake. The 5-km-wide (3.1 miles) 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 has grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.

Featured image credit: Ray in Manila

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