The Philippine Institute of Volcanology and Seismology (Phivolcs) said unrest at the volcano in Batangas “has markedly declined” following the phreatomagmatic eruption on March 26 and six weak phreatomagmatic bursts until March 31.
First, there was a “significant drop in volcanic degassing from the main crater.”
Phivolcs noted that sulfur dioxide (SO2) emissions were elevated in the first three weeks of March and peaked at 21,211 tons per day on March 16, then “suddenly dropped” last Sunday, April 3.
Since then, SO2 emissions have averaged 240 tons per day, and even decreased to 103 tons on Friday, April 8, “the lowest flux recorded since unrest began in 2021.”
“The rise in SO2 emissions prior to the March 26 phreatomagmatic eruption and its subsequent drop indicate that accumulated volcanic gas drives this type of eruptive activity at the main crater. Recent volcanic gas emissions, therefore, suggest that the potential for eruptive activity at present is low,” Phivolcs explained.
Only “occasional weak plumes” were observed from the main crater in the past week as well, “consistent with the significant decrease in magmatic degassing.”
Second, the number of volcanic earthquakes fell.
According to Phivolcs, “only 86 small-magnitude and imperceptible volcanic earthquakes have been recorded by the Taal Volcano Network” since March 26.
“These consist of 26 volcanic tremors, 59 low-frequency volcanic earthquakes, and 1 volcano-tectonic event, most of which occurred 0 to 7 kilometers beneath the main crater and the eastern sector of Taal Volcano Island,” state volcanologists said.
“In addition, background tremor associated with shallow hydrothermal activity ceased on March 31. There has been no recorded seismic activity related to new magmatic intrusions from Taal’s deeper magma source since unrest began last year.”
Phivolcs emphasized, however, that the downgrade to Alert Level 2 does not mean the unrest has completely stopped.
“Alert Level 2 means that there is decreased unrest but should not be interpreted that unrest has ceased or that the threat of an eruption has disappeared,” the agency said.
If volcanic activity escalates again, Taal Volcano could be raised back to Alert Level 3. But if the downtrend continues, the volcano could be further downgraded to Alert Level 1.
Under Alert Level 2, the following could occur:
- sudden steam-driven or phreatic explosions
- volcanic earthquakes
- lethal accumulations or bursts of volcanic gas
Phivolcs recommended that entry into Taal Volcano Island, a permanent danger zone, remain prohibited. – Rappler.com