Watch more in iWantv or TFC.tv

MANILA — State seismology institute Phivolcs on Thursday identified 2 factors on why the Taal lake and a river in Batangas province dried up following the eruption of a volcano there last weekend.

Set in the middle of a picturesque lake, Taal Volcano on Sunday belched an ash column that drifted towards Metro Manila and spewed a lava fountain the next day.

According to Phivolcs Director Renato Solidum, the eruption could have vaporized the water in Taal's main crater.

"Dahil po iyong lalim ng main crater ay mas mababa sa taas ng Taal Lake, may hydraulic gradient o slope iyan, kaya iyong tubig po ay papasok ngayon sa isla at bababa lake level," he told ABS-CBN News.

(Because the main crater is shallower than Taal Lake, there is a hydraulic gradient o slope there, so the water will flow to the island and the lake's level will drop.)

The Pansipit River flows into the Taal Lake. Any change in the lake's depth will affect the river, he added.

The lake's level could have also dropped due to "ground deformations" caused by the quakes spawned by the volcano, said Solidum.

"Posible kasi na bumabagsak ang ibang parte ng lawa at iyong ibang parte naman ay umaangat," he said.

(It's possible that some parts of the lake is dropping and other parts are rising.)

Huge cracks, he noted, recently opened in Lemery, Agoncillo and Talisay towns due to the quakes, which are likely caused by magma rising towards the volcano's crater.

In the past 24 hours, Phivolcs recorded 494 quakes triggered by Taal, of which 14 were felt, the strongest at a "weak" magnitude 3, said Solidum.

Taal also continued bleching an 800-meter ash plume and about 4,100 tons of sulfur dioxide per day, he said.

The volcano remains under the second highest danger level, which means a "hazardous explosive eruption is possible within hours to days," said Phivolcs.