Phivolcs: Tagaytay Ridge not high-risk area for eruption

Published January 18, 2020, 12:00 AM

by manilabulletin_admin

By Alexandria San Juan

Despite being inside the 14-kilometer danger zone, parts of Tagaytay will not be facing direct hazards of a possible volcanic eruption, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.

PHIVOLCS Director Usec. Renato Solidum explains the maintained Alert Level 4 of Taal volcano by stating that a hazardous eruption may still occur “within hours to days.” He also said that magma is still rising within Taal, as indicated by persistent volcanic earthquakes in the vicinity. (PHOTO/ ALVIN KASIBAN)
PHIVOLCS Director Usec. Renato Solidum explains the maintained Alert Level 4 of Taal volcano by stating that a hazardous eruption may still occur “within hours to days.” He also said that magma is still rising within Taal, as indicated by persistent volcanic earthquakes in the vicinity. (ALVIN KASIBAN / MANILA BULLETIN)

Phivolcs director Renato Solidum, Jr. said Tagaytay Ridge, although inside the danger zone, is not considered as a high-risk area due to its high elevation, and will not be directly affected by volcanic hazards such as base surge and volcanic tsunami. He said based on their mapping, not all areas inside the danger zone need to evacuate but only those identified in the hazard maps developed by Phivolcs.

“Ang mga lugar na ini-rekomenda natin for a total evacuation ay ang Taal Volcano Island at high-risk areas na nakalagay sa mapa na nasa loob ng 14-kilometer radius mula sa Taal Main Crater at along sa Pansipit River Valley,” he said.

“For example, ang Tagaytay City ay nasa loob ng 14-kilometer radius pero yung [Tagaytay] Ridge at national road ay hindi kasama sa mga posibleng tamaan ng base surge so, hindi nila kailangan mag evacuate. ‘Yung mga lugar na mataas ang elevation katulad ng Tagaytay, na kahit nasa 13- to 14-kilometer radius, ay masyado nang mataas para abutin ng base surge na ang galaw ay pa-[horizontal].”

However, Solidum pointed out that those in the elevated areas are still vulnerable to ash fall, which is dangerous to the health.

Volcanic Hazards

Alert Level 4 remains in effect over Taal Volcano almost a week after it erupted on Sunday (Jan.12), which means a hazardous explosive eruption is still possible within hours to days.

Phivolcs strongly reiterates total evacuation from Taal Volcano Island, which was tagged by the agency a permanent danger zone due to volcanic hazards that killed thousands of people in its previous eruptions.

Among these hazards, Phivolcs said, is the base surge, which is a turbulent mass of volcanic ash, rocks, and hot gases that laterally flows away from the base of an eruption column at very high speeds.

Base surge could cause casualties mainly from gas suffocation and shock wave impact, or injuries such as burns due to hot sand and ash.

Authorities have also warned of a possible volcanic tsunami which can be triggered by falling debris after an eruption, pushing the water and generating waves.

Another hazard comes from ballistic projectiles or rocks blasted into the air during an eruption. These usually land within two kilometers of the vent but can travel as far as five kilometers or even further if the eruption is very explosive.

Hazard maps

To prevent casualties and damage brought by these hazards, Phivolcs developed maps that show areas that might be affected by each indicated hazards such as possible ballistic projectiles, base surge, and volcanic tsunami.

 
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