By ALEXANDRIA DENNISE SAN JUAN and NOREEN JAZUL
Taal Volcano's danger status was lowered on Thursday to Alert Level 1 after state seismologists observed a decrease in volcanic earthquakes and surface activity at the main crater in the past days.
However, the Philippine Institute for Volcanology and Seismology (Phivolcs) said that despite the overall decreasing trend in the level of its monitoring parameters, Taal Volcano is still at an "abnormal" state of unrest.
The main crater of the Taal Volcano is seen during an aerial survey done by government officials, more than a week after the eruption of Taal Volcano in Batangas. (Mark Balmores / MANILA BULLETIN FILE PHOTO)
"Alert Level 1 means that the volcano is still in abnormal condition and should not be interpreted that unrest has ceased or that the threat of an eruption has disappeared," Phivolcs explained.
The alert may be upgraded should parameters "forewarn of renewed unrest," the state volcanology bureau added.
According to the agency, the lowering of Taal's alert status was due to the overall decreasing trend in the level of its monitoring parameters.
Phivolcs said low-level volcanic earthquake activity, stabilizing ground deformation of the Taal Caldera and the Taal Volcano Island edifices, and weak surface activity at the Main Crater and the Daang Kastila fissure have been observed for over a month since the volcano stepped-down to Alert Level 2 on February 14.
A decline in the daily average of volcanic earthquakes was also recorded by the Taal Volcano Network from 141 events a day between January 26 and February 14, to only 31 from February 14 to March 19.
"Majority of these earthquakes were associated with rock-fracturing processes and only six low-frequency events associated with magmatic or hydrothermal activity were detected until March 6," Phivolcs said.
Sulfur dioxide levels also fell below detection limits over the past weeks while surface activity dwindled to weak emission of 50 to 100-meter tall steam-laden plumes from active gas vents on the Main Crater and along the Daang Kastila fissure on the northern flank of the volcano island.
Despite the downward trend of Taal's volcanic activities, Phivolcs said that sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ash fall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within the volcano island under Alert Level 1.
Residents of areas at high risk to base surges who have returned were advised to remain vigilant and "always be prepared for a quick and organized evacuation."
Phivolcs also reiterated its warning that entry into the volcano island, which was tagged as a permanent danger zone, particularly the vicinity of the Main Crater and the Daang Kastila fissure, must remain "strictly prohibited."
Local government units were advised to continuously assess previously evacuated barangays around Taal Lake for damages and road accessibility and to strengthen preparedness, contingency, and communication measures in case of renewed unrest.
Residents were also urged to observe precautions due to ground displacement across fissures, possible ash fall, and minor earthquakes.
Taal Volcano spewed ash and lava on January 12 and 13 which surprised residents and tourists who were visiting the picturesque lake.
The 50,000-feet-tall ash cloud blanketed nearby towns, displaced thousands of residents, and disrupted business in surrounding areas.
Taal, one of the most active volcanoes in the country, has erupted more than 30 times in the past five centuries, and most recently in 1977.
Although tagged as the world's smallest volcano, Taal is also one of the deadliest following its violent eruptions in 1754, 1911, and 1965 leaving thousands of casualties due to various volcanic hazards that it brought.