About 259 volcanic earthquakes were recorded in Taal Volcano in the past 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported Wednesday.
The number includes 236 episodes of volcanic tremor that lasted one minute to 22 minutes and four hybrid earthquakes.
Volcanic quakes are caused by movements or eruptions of magma from the volcano. Hybrid earthquakes indicate rock fracturing and magma or fluid movement.
Taal Volcano, which remains under alert level 2 (increased unrest), may have sudden steam-driven or phreatic explosions, volcanic earthquakes, and minor ashfall. Lethal accumulations or expulsions of volcanic gas can occur and threaten areas within the Taal Volcano Island (TVI).
Phivolcs Director Renato Solidum Jr. earlier said determining the appropriate alert level for a volcano not only depends on the number of earthquakes recorded, but also the type of earthquakes, location, depth, and energy of the quakes.
Ground deformation, the chemistry of gases and water, and surface manifestations are other parameters being considered, he added.
For the past 24 hours, Phivolcs has observed weak emission of steam-laden plumes from fumarolic vents that rose 10 meters.
Sulfur dioxide emission that averaged 813 tons per day was measured on Tuesday.
Temperature highs of 71.8°C and pH of 1.59 were last measured from the main crater lake on March 4 and February 12, respectively.
Phivolcs reiterated that entry into the TVI, a permanent danger zone, especially the vicinities of the main crater and the Daang Kastila fissure, must remain strictly prohibited.
Local government units were also advised to continuously assess and strengthen the preparedness of previously evacuated barangays around Taal Lake in case of renewed unrest. PNA.GOV.PH