Phivolcs: Steep lava increases danger of sudden pyroclastic flows

By Marlon Atun

LEGAZPI CITY --- The ongoing eruption at Mayon Volcano is creating a lot of unstable volcanic materials, raising concerns about sudden and dangerous flows known as pyroclastic density currents (PDCs).

This has led the Philippine Institute of Volcanology and Seismology (Phivolcs) to issue new warnings.

Since the eruption began, more than 61 million cubic meters of fresh volcanic material have piled up on Mayon’s slopes, according to Paul Karson Alanis, senior science research specialist of Phivolcs.

This newly formed lava is steep and unstable, making it prone to sudden collapses, Alanis said.

Alanis explained that these fresh deposits, found in the Miisi, Bonga, and Basud gullies, can easily be disturbed.

“These materials are fresh and unstable. Even minor explosions or rockfalls can trigger a collapse, similar to what occurred on May 2,” Alanis said.

On May 2, a strombolian eruption occurred at Mayon Volcano, which was followed by the release of heavy ash clouds and continuous pyroclastic density currents (PDC), the largest PDC in recent months.

The event sent quick-moving volcanic gas, ash, and debris rushing down the Miisi gully.

Alanis warned that these dangerous flows can happen not just in one area but can also affect the Bonga or Basud gullies and even spread beyond known paths without any warning.

Phivolcs emphasizes the need to strictly enforce a 6-kilometer safety zone around the volcano, or the Permanent Danger Zone (PDZ).

Doreen Abelinde, who oversees the Mayon Volcano Observatory, stressed that this entire area is hazardous and should not be entered under any circumstances.

Abelinde said that even if the alert level for Mayon drops in the future, the risks will still remain.

Newly formed lava can take a long time—sometimes years—to cool down and might still trigger explosions, especially if internal temperatures remain very high, she added.

With the rainy season approaching, Alanis also highlighted the risks posed by heavy rainfall.

If it rains heavily—around 300 to 350 millimeters during storms—this can make loose volcanic materials unstable, potentially leading to lahars (mudflows) or debris flows that could threaten nearby communities, he said.

These materials, when soaked by rain, can move quickly and pose serious dangers to lives and properties in low-lying areas along rivers, he added. (PIA Bicol)