The emission of sulfur dioxide (SO2) from Taal Volcano in Batangas reached a new high on Saturday, July 3.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said in an advisory on Saturday evening that SO2 emission averaged at 14,699 tons per day, “the highest ever recorded in Taal.”

Upwelling, or the rising of hot volcanic fluids to the surface, also generated steam-rich plumes rising 2,500 meters or 2.5 kilometers above Taal Volcano Island.

Phivolcs warned that the new spike in SO2 emission could be followed by another eruption at the main crater.

That would be similar to how increased levels of SO2 – particularly 14,326 tons per day last Monday, June 28, and 13,287 tons per day recorded on Thursday morning, July 1 – “preceded the short-lived phreatomagmatic eruption” on Thursday afternoon.

High SO2 indicates magma is already at a shallow level or near the surface of the volcano.

As Phivolcs put it, “current SO2 parameters indicate ongoing magmatic extrusion at the main crater that may further drive succeeding explosions.”

The agency also said the high SO2 could lead to the formation of more volcanic smog or vog in areas surrounding Taal Lake.

“Because of unprecedented high SO2 degassing from Taal main crater, local government units are additionally advised to conduct health checks on communities affected by vog to assess the severity of SO2 impacts on their constituents and to consider temporary evacuation of severely exposed residents to safer areas,” Phivolcs said.

Last Thursday’s phreatomagmatic eruption had prompted Phivolcs to place Taal Volcano under Alert Level 3. This alert level means there is magmatic unrest.

Phivolcs stressed on Saturday evening that Taal Volcano Island, Taal Lake, the barangays of Bilibinwang and Banyaga in Agoncillo town, and the barangays of Buso-buso, Gulod, and Bugaan East in Laurel town must remain off-limits to all.

If a strong eruption occurs, there could be pyroclastic density currents, which are clouds of hot gas, ash, and other volcanic debris. A volcanic tsunami is also possible since Taal Volcano is situated within Taal Lake. – Rappler.com