Short-lived phreatomagmatic bursts at Taal volcano, Philippines

Short-lived phreatomagmatic bursts at Taal volcano, Philippines

Three short-lived phreatomagmatic bursts, lasting between 1 and 5 minutes, were recorded at Taal volcano, Philippines on November 22, 2021, ejectnig plumes up to 1.5 km (4 900 feet) above the crater. The volcano remains at Alert Level 2 (Increased Unrest).

In 24 hours to 00:00 UTC on November 23, the Taal Volcano Network recorded 30 volcanic earthquakes, including 23 volcanic tremor events having durations of 2 to 5 minutes, 4 low-frequency volcanic earthquakes, 3 hybrid volcanic earthquakes and low-level background tremor that has persisted since July 7, 2021.1

In addition, three short-lived phreatomagmatic bursts were recorded during the period, at 00:11 UTC, 12:17 UTC, and 12:34 UTC, lasting 1 to 5 minutes and producing plumes 200 to 1 500 m (650 - 4 900 feet) that drifted southwest.

Activity at the Main Crater was dominated by upwelling of hot volcanic fluids in its lake which generated plumes 2 100 m (6 900 feet) tall that drifted southwest. Sulfur dioxide (SO2) emission averaged 6 643 tonnes/day on November 22.

Based on ground deformation parameters from electronic tilt, continuous GPS and InSAR monitoring, Taal Volcano Island has been inflating since August 2021 while the Taal region continues to undergo very slow extension since 2020.

Alert Level 2 (Increased Unrest) remains over Taal Volcano. DOST-PHIVOLCS reminds the public that at Alert Level 2, sudden steam- or gas-driven explosions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within and around TVI.

DOST-PHIVOLCS strongly recommends that entry into Taal Volcano Island, Taal’s Permanent Danger Zone or PDZ must be strictly prohibited, especially the vicinities of the Main Crater and the Daang Kastila fissure, and extended stays on Taal Lake.

Local government officials are advised to continuously assess and strengthen the preparedness of previously evacuated barangays around Taal Lake in case of renewed unrest.

Civil aviation authorities must advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircraft.

DOST-PHIVOLCS is closely monitoring Taal Volcano’s activity and any new significant development will be immediately communicated to all stakeholders.

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 miles) 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 (3.1 miles) 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 the area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.2

References:

1 TAAL VOLCANO BULLETIN 23 November 2021 8:00 AM - PHIVOLCS

2 Taal - Geological summary - GVP

Featured image credit: Copernicus EU / Sentinel-2. Acquired on November 8, 2021.


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