PHIVOLCS doesn’t expect similar scenario as 2020 Taal Volcano eruption

Taal Volcano's eruption on Thursday, which gave rise to a phreatomagmatic plume, is a different scenario from the January 2020 eruption, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said Thursday.

In a live briefing, PHIVOLCS volcano monitoring eruption and prediction division chief Ma. Antonia Bornas said one way the situation is different is the magma below the volcano has been de-pressurized as a phreatomagmatic eruption involves both magma and steam.

“Nung bago po pumutok ang Taal, ito po ay closed system, no? So ‘yung magma po na nakaimpok po sa pinakailalim pa po ng Taal ay pressurized pa. Kaya po nung pumutok ay napakabilis ng akyat ng magma at napakalakas,” she said.

[Before Taal erupted, it was a closed system. The magma stored under the volcano was pressurized, so when it erupted the magma rose quickly and with force.]

“De-pressurized na ‘yung magma, open-system na po ang Taal, nakakapag de-gas na po siya ng dire-diretsyo, at nawawalan po siya ng pwersa na naninigas… at hindi po nakakapag-ipon ng gas overpressure,” Bornas added.

[The magma is now de-pressurized, so Taal is now an open system. It can now degas directly and it is not storing gas overpressure.]

The January 2020 eruption, meanwhile, was a phreatic, or steam-driven, eruption.

PHIVOLCS Director Renato Solidum said that the volcano will continue to emit sulfur dioxide. However, he said future eruptions will be hard to predict.

“Nasa Alert Level 3 tayo at ‘yung pacing ng activity ng Bulkang Taal… hindi mabilis kumpara sa last year. So ibig sabihin mas nagde-degas ang magma. Mas maiigi nga ‘yan para ‘yung explosion ay hindi masyadong malaki,” he said.

[We are at Alert Level 3 and Taal's pacing activity is slow compared to last year. That means the magma is degassing. That is better as the explosion will not be as big.]

“’Yung scenario na puwede natin makita, puwedeng ganyan lang muna o puwede rin namang mag-escalate. Pero so far wala tayong nakikitang kakaiba doon sa pamamaga ng bulkan,” he added.

[We can't tell if it will remain that way or if it will escalate. But so far we are not seeing anything unusual from the volcano.]

Phreatomagmatic eruption more dangerous

Bornas said that a phreatomagmatic eruption is more dangerous than a phreatic eruption as it has more hazards.

“Definitely po mas delikado yung phreatomagmatic eruption dahil nandiyan na po yung interaction ng magma sa tubig, no?” she said.

“Kung ang magma po ay dire-diretsyo pong nilalabas ay maari pong tuloy-tuloy ‘yung phreatomagmatic eruption. Meron pong mga matitinding volcanic hazards na kaugnay ng phreatomagmatic eruption,” she added.

[A phreatomagmatic eruption is more hazardous because it involves the interaction of magma with water. If the magma is being expelled directly it is possible that the phreatomagmatic eruption will be continuous. There are severe volcanic hazards associated with a phreatomagmatic eruption.]

Bornas said the hazards of a phreatomagmatic eruption include base surges or pyroclastic density currents, as well as volcanic tsunamis. The US Geological Society defines a base surge as a cloud of gas and suspended solid debris that moves radially outward at high velocity from the base of an eruption.

“Dahil kapag ang base surge po ay pumasok na ng lawa, ito po ay nakakapag-displace ng tubig. At sa atin pong mga historical records ng mga dating pagputok, tuwing meron pong base surge ay nagkakaroon po ng volcanic tsunami,” Bornas said.

[When a base surge enters the lake, it can displace the water. And according to historical records, when there was a base surge there would also be a volcanic tsunami.] 

According to Bornas, the volcanic ash created by a phreatomagmatic eruption is muddy and fine, similar to the ash fall experienced in 2020.

Infrastructure may also collapse should ash end up gathering due to continuous phreatomagmatic eruptions. 

At present, however, PHIVOLCS said that the ashfall is concentrated around the main crater of the Taal Volcano.

“Dahil meron pong kaugnay na magma ang phreatomagmatic eruption, maari pong magkaroon ulit tayo ng minor fissuring katulad po ng naranasan natin last year; kung saan po umuurong, gumagalaw po ‘yung magma syempre may mababakante na mga puwang sa ilalim ng bulkan,” Bornas said.

[Because a phreatomagmatic eruption includes magma, we may possibly get another minor fissuring, such as what we saw last year. When the magma moves, of course there will be vacant places under the volcano.]

PHIVOLCS has placed Taal Volcano on Alert Level 3. — BM, GMA News