Manila: Monitoring parameters such as volcanic earthquake occurrence and sulfur dioxide emission have dropped significantly when volcanic tremor, which lasted for several days, stopped in Taal Volcano. Volcanic tremor lasted for five days and 173 minutes, or from 3:37 a.m. of July 9 to 6:30 a.m. of July 11, Philippine Institute of Volcanology and Seismology (Phivolcs) Director Teresito Bacolcol said on Monday.

According to Philippines News Agency, "Based on our data, sulfur dioxide emission dropped from 1,290 tonnes on July 9 to 365 tonnes on July 12," Bacolcol told the Philippine News Agency in an interview. He added that no low-frequency volcanic earthquake was recorded since July 12.

A volcanic tremor is triggered by the continuous flow of magma or gas inside a volcano. Volcanic earthquake, on the other hand, usually happens when rocks inside the volcano break or crack. Bacolcol said it is possible that a tremor would persist soon after it had stopped. "In fact we had a tremor in the past which lasted for 90 days (from April 8, 2021 to July 7, 2021), had a pause for a few hours, then continued again for another 221 days, or from July 7, 2021 to Feb. 14, 2022," Bacolcol said. He also clarified that even when a tremor stops, it does not necessarily mean that monitoring parameters would decline.

Meanwhile, Taal Volcano is still under Alert Level 1 (low-level unrest) which means sudden steam-driven or phreatic or minor phreatomagmatic eruptions, minor ashfall, and lethal accumulations or expulsions of volcanic gas could occur. The Phivolcs chief, however, said there is always a possibility of a phreatic eruption even when a volcano is at alert Level 0 or normal.