The Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday lowered the status of Taal Volcano to Alert Level 2 (decreased unrest), three weeks after it was put under Alert Level 3 (decreased tendency towards hazardous eruption) on January 26.
Lowering its alert level status was due to fewer volcanic earthquakes and weak steam or gas emission at the main crater for the past three weeks.
According to Phivolcs, a daily average of 141 volcanic earthquakes has been recorded since January 26.
Volcanic earthquakes are caused by movements or eruptions of magma from the volcano.
Sulfur dioxide (SO2) emission, on the other hand, had an average of 62 tons per day since January 26, consistent with diminished plume activity or absorption of volcanic gas by a recovering lake at the main crater.
Activity in the main crater has been characterized by the generation of weak steam laden plumes, consistent with decreased magmatic unrest.
Phivolcs executive director Renato Solidum Jr. earlier explained that a weaker eruption is based on the height of the plume coming out of the crater. Volcanic plume or eruption plume is a column of hot volcanic ash and gas emitted into the atmosphere during an explosive volcanic eruption.
He also said magmatic activity means processes involving magma, which include breaking of rocks and filling of cracks by magma or volcanic gas, movement of magma, and degassing of magma, boiling of underground water by magma.
Phivolcs, meanwhile, noted that despite the lowering of the status of Taal Volcano, it does not mean that unrest has ceased, as there is still an imminent threat of an eruption.
In a previous interview with the Philippine News Agency (PNA), geologist Carlos Arcilla said that so long as there is presence of sulfur dioxide emissions, earthquakes, and volcanic inflammation, there is risk for an eruption.
Confirming that nobody can predict when an eruption could occur, Arcilla noted that even if an eruption subsides for one month, it would not mean that there is no risk for a hazardous explosive eruption.
Phivolcs said those residing within areas at high risk to base surges who have returned after the Alert Level 2 announcement must be prepared for a quick and organized evacuation.
Entry into Taal Volcano Island, Taal's permanent danger zone, must be strictly prohibited, it added.
Local government units are likewise advised to additionally assess previously evacuated areas within the 7 km. radius for damage and road accessibility, and to strengthen preparedness, contingency, and communication measures in case of renewed unrest.
Source: Philippines News Agency