Deadly, destructive: Geologist spells out dangers of volcanic eruptions


Posted at Jan 14 2020 12:49 PM | Updated as of Jan 14 2020 01:11 PM

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MANILA - The possibility of a hazardous explosive eruption remains in Taal Volcano, which has prompted the evacuation of residents living on the island where it is located.

On ANC's Headstart, Mahar Lagmay of the University of the Philippines Resilience Institute reiterated hazards associated with volcanic eruption.

These include ash, pyroclastic flows, tsunami, landslide, or seiche or oscillation of lake water.

Pyroclastic flow, he said, is hot and travels at high speed, decimating those on its way. 

"You can die like the people in Pompeii," he said, referring to the ancient Roman city destroyed by the catastrophic eruption of Mount Vesuvius in 79 A.D. 

He said these hazards have already been seen since the volcano started acting up on Sunday. 

Hazardous eruption can kill, Lagmay said. 

He explained that magma that extrudes to the surface gets broken down into ashes and smaller pieces because of the explosion. The ashes are then carried into the cloud and its plumes.

"And that's very dangerous. If you're in the island, that's the reason why people have evacuated, chances are you will die," he said.

Thousands have fled their homes after Taal erupted on Sunday, prompting the overnight closure of Manila's main airport and the suspension of work and classes.

"If a hazard happens without any people, there's no disaster. It's good that the activity is confined within the island and there's lake water surrounding it," said Lagmay.

However, when there's a bigger eruption like the scale of that of Mt. Pinatubo in 1991, where the volcanic explosivity index was at VEI 6, it can be hazardous.

"The eruption that happened in Taal island generated a plume that was I think 15 kilometers and ash was spewed, penetrated the stratosphere and the ashes reached up to Nueva Ecija--- that's a very explosive eruption," he explained.

A volcanic tsunami is also a possibility, he said.

"If the explosion is large, if in the days to come if it's going to happen there might be disturbance in the lake water of Taal and that might create a tsunami," he said.

The condition at Taal volcano remains at alert level 4 which means a hazardous explosive eruption is possible within hours to days, according to Phivolcs.

"If that is what they are saying that there's still an imminent possibility of a large eruption just like Pinatubo, then it is hazardous," he said.

Phivolcs has recorded more than 200 volcanic earthquakes in the area. 

"The fact that there are earthquakes means magma is trying to push up towards the surface of the earth," Lagmay said.

This magma intrusion may lead to further eruptive activity, Phivolcs said.

Sunday's Taal eruption prompted Phivolcs to raise the alert level to 4 in just a matter of hours.

"It’s strange that suddenly the magma is on the surface because there are many tell-tale signs that we can see before the magma reaches the surface because it comes from the deep bowels of the earth, probably about 10 kilometers. And during transit, there are many indicators that can tell us the magma is rising and near the surface already," Lagmay said.

"Nature has its own way, Phivolcs did their best," he said.

Meanwhile, Lagmay clarified that climate change has nothing to do with Taal's eruption.

"If the eruptions are big, they do affect the climate but the climate change itself does not affect the magma's behavior as it rises towards the surface of the earth," he said.