Phreatomagmatic eruption at Taal volcano, Alert Level raised to 3, Philippines

A phreatomagmatic eruption took place at Taal volcano, Philippines at 07:16 UTC (15:16 LT) on July 1, 2021, generating a short-lived dark plume up to 1 km (3 300 feet). Anomalously high volcanic SO2 gas emission preceded the eruption, averaging 14 241 tonnes/day and 13 287 tonnes/day on June 28 and July 1, respectively. A marked increase in volcanic gas upwelling also began on June 28, generating plumes that rose some 3 km (9 840 feet) above Taal Volcano Island.

In view of the above, DOST-PHIVOLCS has raised the alert status from Alert Level 2 to 3.

"This means that there is magmatic intrusion at the Main Crater that may further drive succeeding eruptions," PHIVOLCS said.

The agency strongly recommends Taal Volcano Island and high-risk barangays of Agoncillo and Laurel, Batangas be evacuated due to the possible hazards of pyroclastic density currents and volcanic tsunami.

Image credit: PHIVOLCS

The public is reminded that the entire Volcano Island is a Permanent Danger Zone (PDZ), and entry into the island as well as high-risk barangays of Agoncillo and Laurel is prohibited.

In addition, communities around the Taal Lake shore are advised to take precautionary measures and be vigilant of possible lakewater disturbances related to the ongoing unrest.

High levels of volcanic sulfur dioxide or SO₂ gas emissions and tall, steam-rich plumes have been observed over the Taal Main Crater since this past weekend, PHIVOLCS reported on Tuesday, June 29, 2021.

SO₂ emission on June 28, 2021, averaged 14 326 tonnes/day — the highest ever recorded in Taal — and 13 287 on July 1.

SO₂ emission over Taal three hours before the eruption on July 1, 2021. Credit: ADAM Platform, Antonio Vecoli

On June 29, PHIVOLCS has received reports of adverse effects on some residents of lakeshore Tanauan City and Talisay Municipality facing Taal Volcano Island, and on some workers of aquaculture in Taal Lake, have been received by DOST-PHIVOLCS.

Update:

Today's eruption lasted 5 minutes based on visual monitors. The event recorded mid-course as a low-frequency explosion earthquake but was not preceded by seismic or ground deformation precursors.

Four additional phreatomagmatic bursts have occurred that lasted no longer than 2 minutes each and produced short jetted plumes that rose 200 m (660 feet) above the Main Crater Lake. These events occurred at 18:26 LT, 19:21, 19:41 and 20:20 LT.

Upwelling of the Main Crater Lake that began at 12:07 UTC (20:07 LT) is ongoing as of 16:00 UTC.

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 (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. (GVP)

Featured image credit: PHIVOLCS