Watch out for lahar, Albay folk warned
LEGAZPI CITY—Government volcanologists on Thursday warned that huge volumes of volcanic debris generated by Mayon Volcano’s continuing eruption could trigger renewed ashfall as well as dangerous lahar flows amid the expected onslaught of a tropical storm in the coming days.
In its latest report, the Philippine Institute of Volcanology and Seismology (Phivolcs) said the total volume of magma ejected by Mayon so far has reached an estimated 66.2 million cubic meters.
The agency said the two major pyroclastic density current (PDC) events that descended the Mi-isi Gully on May 2 were the largest recorded since Mayon’s unrest this year began.
PDCs, locally called “uson,” are fast-moving mixture of hot volcanic gas, ash and rock fragments capable of burning, burying, and destroying everything along its path.
The first PDC event on May 2 lasted 39 minutes, while the second, a stronger and more sustained flow, continued for 95 minutes.
“It carved a new deep gully on the upper Mi-isi channel and deposited around 4.6 million cubic meters of volcanic materials along the Mi-isi-Binaan Channel,” said Ma. Antonia Bornas, chief of Phivolcs’ Volcano Monitoring and Eruption Prediction Division.
On Thursday, a collapse-fed PDC descending through the Mi-isi Gully was recorded on the volcano’s southwestern slopes at 8:39 a.m.
Alert level 3
Phivolcs’ 24-hour observation bulletin on Thursday showed continuing lava effusion in the Basud and Mi-isi gullies, extending about 3.2 kilometers and 1.6 km, respectively. This was accompanied by minor eruptions and ash emission.
During the observation period, Mayon generated 10 volcanic earthquakes, including six volcanic tremors lasting from 2 to 34 minutes, as well as 297 rockfall events.
Ashfall was also reported to blanket parts of Albay, affecting an estimated 8,544 hectares as volcanic activity continued.
According to Phivolcs, Mayon remains on alert level 3, which signifies increased or magmatic unrest, hence entry into the 6-km permanent danger zone is prohibited.
Bornas said the PDCs were generated by continuing lava collapse at Mayon’s summit crater, producing massive ash clouds that drifted westward due to strong winds.
Ashfall affected four towns and cities and 109 villages, based on reports from local governments, disaster response units and the Phivolcs quick response team.
Phivolcs warned that newly deposited volcanic debris could generate dangerous lahar during heavy rains.
The agency added that lahar from the deposits could reach volumes comparable to those generated during Supertyphoon “Reming” (international name: Durian) in 2006 if massive erosion occurs in a single event.
Phivolcs also warned that fresh deposits remain extremely hot, with temperatures possibly exceeding 500 degrees Celsius, and may trigger secondary explosions if disturbed.
Since Jan. 1, Phivolcs has recorded 8,926 volcanic earthquakes, 2,291 PDC signals, and 36,738 rockfall events.
Prepare to flee
Phivolcs advised communities within the 7-km radius of the crater to prepare for possible evacuation if large PDC events recur.
Residents living near river channels draining Mayon, particularly along the Mi-isi-Binaan Channel, were also urged to remain alert for lahar and sediment-laden flows during heavy rains.
Daraga Mayor Victor Perete said security measures had been tightened in Barangay Mi-isi, with additional personnel sent by the Albay provincial police.
“We have also requested assistance from the Department of Agriculture for the 798 farmers affected by the ashfall,” Perete told the Inquirer.
He said the local government was seeking long-term aid as farms had been heavily damaged by the eruption.
“We also fear possible lahar flows because debris from the recent PDCs has caused gullies, some as deep as 100 meters, to overflow and create new pathways that now pose danger to five villages,” Perete said.
He said local officials would coordinate with experts from Phivolcs and the Mines and Geosciences Bureau to mitigate hazards.
“All residents within the 6-km danger zone are secured in relocation sites, but those seeking voluntary relocation for safety will also be validated,” Perete added.
