LEGAZPI CITY: Following the increasing restiveness of Mount Mayon, the Philippine Institute of Volcanology and Seismology (Phivolcs) on Monday raised to Level 2 the alert status over the volcano in Albay province.

Dr. Paul Alanis also told The Manila Times that a deadly pyroclastic flow might occur if the lava dome of the volcano collapses.

A pyroclastic flow is a fast-moving current of hot gas containing a high-density mix of hot lava blocks, pumice, ash and volcanic gas, Alanis explained. The pyroclastic can tumble at a very high speed down volcanic slopes with extreme temperatures of rocks and gas generally between 200 C and 700 C (390-1300 F) and can ignite fires, he added.

The possible direction of pyroclastic flow, Alanis said, is the southeast quadrant of the volcano and could be a threat to Legazpi City and the municipalities of Sto. Domingo, Daraga and Camalig.

It can be recalled that in 1993, at least 77 farmers were killed after a pyroclastic flow tumbled down the slopes of Mount Mayon generated by the sudden phreatic explosion.

Legazpi City Mayor Geraldine Rosal, meanwhile, issued a directive to the City Disaster Risk Reduction and Management Office (CDRRMO) and Climate Change Resilience Council to be ready with contingency plans to ensure the safety of the public.

In her directive, Rosal told the barangay (village) leaders along the slope of the Volcano, such as Mabinit, Buyuan, Matanag, Bogña and Padang, to take all necessary precautionary measures and constantly monitor the alerts issued by the Phivolcs and the local government units.

“The public is reminded that entry in the six-kilometer permanent danger zone and other activities like ATV rides, mountain climbing, hiking and quarrying must be strictly avoided due to the increase in the chances of sudden stream-driven or phreatic explosion as well as perennial hazards or rock falls, avalanches and ash burst at the summit area that may occur without warning,” Rosal said.

Residents living in valleys and active river channels are cautioned to remain vigilant against sediment-laden stream flows and lahar in the event of prolonged and heavy rainfall brought by the advent of the rainy season and all are enjoined to properly coordinate with the CDRRMO.

Rock fall

Phivolcs chief Teresito “Toto” Bacolcol said that since last the week of April, daily visual and camera monitoring of the summit crater revealed an increase in rock fall from the volcano’s summit lava dome indicating aseismic growth.

“Rock fall increased in frequency from an average of five events a day to 49 events per day from 5 a.m., June 4 to 5 a.m., June 5,” Bacolcol said.

Since April, the agency said a total of 318 rock fall events have been recorded by the Mayon Volcano Network while 26 volcanic earthquakes have been recorded for the same period.

The advisory explained that the longer-term ground deformation parameters based on electronic distance measuring, precise leveling, continuous global positioning system, and electronic tilt monitoring indicate that the volcano is still inflated, especially on the northwest and southeast since 2020.

Phivolcs also said the highest sulfur dioxide (SO2 ) emission was recorded on April 29 at 576 tons and the last measurement on May 23 at 162 tons.

These low-level volcanic earthquakes, ground deformation, and volcanic gas parameters are overshadowed by recent steep increases in rock fall events which may possibly lead to further dome activity, said Bacolcol.

Commercial and private planes on Monday were also advised to avoid areas near the volcano.

Civil Aviation Authority of the Philippines spokesman Eric Apolonio said that flights have been prohibited to operate 10,000 feet from the surface and advised to avoid flying close to the volcanos’ summit as ash from the sudden phreatic eruption can be hazardous to aircraft.