EXPLAINER: 2020 vs 2021 Taal eruption

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Metro Manila (CNN Philippines, July 2) — State volcanologists recently raised the status of Taal Volcano to Alert Level 3 after it spewed a kilometer-high plume of magma and steam, over a year since its last eruption that displaced more than 100,000 people.

Government officials are on alert for its possible increase in activity, with over 1,000 residents already seeking temporary shelter in evacuation centers.

READ: Govt braces for Taal's increased activity, aims for zero casualty 

READ: Alert level 3 raised over Taal Volcano after phreatomagmatic eruption 

But how is this year's eruption different from that of January last year? Should people expect a more dangerous scenario anytime soon?

Phivolcs Director Renato Solidum explained on Friday what constitutes Taal's phreatomagmatic eruption and how different it is from its volcanic activity in 2020.

"A phreatomagmatic eruption happens when magma would actually reach a water surface like the main crater and this interaction — because the magma is hot and water is cooler — it will cause a fracturing explosion," Solidum told CNN Philippines' The Source.

A phreatomagmatic eruption is generated by the interaction of steam, water, and magma (molten rock beneath a volcano) and may drive explosive eruption in the future, he said. This activity prompted the raising of Taal's status to Alert Level 3 on Thursday due to its "high level of volcanic unrest."

"We expect similar styles of eruption. But it is also possible that larger eruptions can happen, larger than yesterday. But for very explosive eruptions, we need to monitor if new magma will ascend from below which would contain more gases," Solidum said.

He explained that in January last year, Taal began a phreatic eruption, driven mainly by steam emissions.

READ: Taal Volcano eruption: Things you need to know 

"Essentially when the explosion happened, the pressure at the crater became much less and the magma beneath Taal which is full of gases...suddenly ascended," he said of last year's explosion.

The Phivolcs director said that Taal's eruptions in the past are usually followed by weaker explosions consisting of lava fountaining which are "not that dangerous," since the volcanic material is confined to the island.

However, he said, since this week's eruption is characterized by steam, magma, and water, it can be "really explosive," could cause a surge of materials "moving down the slopes of the volcano across the lake that can endanger people close to the shoreline."

Worst-case scenario

Solidum did not state whether Taal's status will soon be raised to Alert Level 4 indicating an imminent hazardous eruption. However, he warned of a possible "worst-case scenario" wherein pyroclastic density current or flows of hot ashes and debris will be excreted out of the volcano's main crater, which could trigger volcanic tsunamis.

"Once pyroclastic materials enter the water it can displace the water and trigger volcanic tsunamis that will affect the shorelines," he said.

What we should do for now

Residents living in Taal Volcano Island, which is considered a Permanent Danger Zone, and in high-risk barangays of Agoncillo and Laurel are now urged to evacuate their homes and go to safer areas. Communities around the Taal Lake shore must also take precautionary measures and be vigilant of possible lakewater disturbances.

Evacuees are advised to stay calm, bring their face masks and alcohol, and observe physical distancing in evacuation centers. They must also monitor updates from their local government units all the time, Solidum said.

Officials estimated that evacuation will affect around 3,523 families or 14,495 individuals.

What the government is doing so far

As of Friday, evacuation activities are ongoing. Batangas Provincial Disaster Risk Reduction and Management Office is coordinating with the national government to assess the situation in the province and respond to the affected residents' needs.

More than 1,300 residents already sought temporary shelter in evacuation centers and relatives from safer areas. Other nearby towns were also advised to accommodate evacuees from affected areas to reduce crowding.

Meanwhile, food packs worth ₱1.4M and non-food items worth ₱11M will be distributed to residents, officials said. The military, police and coast guard are also assisting efforts and patrolling on the ground, Malacañang added.

READ: Over 1,200 residents flee to evacuation centers amid Taal unrest 

Solidum said the alert level will be lowered only after a two-week observation of a downward trend in volcanic activity.

READ: Phivolcs: Taal's activities should drop for two weeks before alert level is lowered

This story will be updated as new information comes in on Taal's volcanic activity.