MANILA, Philippines — Heavy rains brought by the tail-end of a cold front have increased the dangers of lahar flowing “on all river channels” near the Mayon Volcano in Albay, the Philippine Institute of Volcanology and Seismology warned Saturday.
In its advisory issued at 10:30 a.m. Saturday, the Phivolcs said the lava, ashfall and other pyroclastic density current (PDC) materials spewed by Mayon Volcano for the last two weeks could turn into lahar if the heavy rains continue.
“These deposits can be remobilized by rainwater and generate lahars by themselves and or by incorporating existing erodible material on channel banks,” the Phivolcs said.
The Phivolcs said lahar and sediment-laden streamflows are possible “on all river channels draining the slopes of Mayon Volcano” especially in the villages of Buyuan, Missi, Mabinit, Basud, San Vicente, Buang, Quirangay and Masarawag-Maninila.
“Communities and local government units beside these river systems are advised to be additionally vigilant and to move residents to high ground when heavy rains occur,” the Phivolcs said.
Mayon remains at Alert Level 4, a notch below the highest alert level as of Saturday.
The Phivolcs said the total volume of PDC deposits on the watershed areas near Mayon, mostly on the Buyuan and Miisi channels, have already reached nine million cubic meters, “excluding unverified deposits on the northern flank.”
Meanwhile, the total volume of ashfall on the western sector is estimated at roughly 1.5 million cubic meters.
“PHIVOLCS therefore warns of potential lahars and sediment-laden streamflows...that may be generated by heavy rainfalls brought about by the cold-front,” Phivolcs said.
Between 6:26 a.m. to 1:40 p.m. on Friday, three episodes of sporadic lava fountaining from the Mayon's summit crater have occured lasting 24 minutes to 40 minutes, the Phivolcs said in its 8 a.m. bulletin issued yesterday.
The Phivolcs said the lava fountains generated ash plumes that reaching kilometers above the crater.
A total of ten volcanic earthquakes, 21 tremor events, three of which correspond to the lava fountaining events, one PDC from lava collapse, and 21 rockfall events were recorded by Mayon's seismic monitoring network.
The continuous volcanic activities have already displaced more than 18,000 families or more than 72,000 individuals from 57 barangays causing overcrowding in temporary shelters.
Mayon, located about 330 kilometres (205 miles) southeast of the capital Manila, is the most active of the country's 22 volcanoes -- and one of the deadliest.
Four foreign tourists and their local tour guide were killed when it last erupted in May 2013.
In 1814, more than 1,200 people were killed when lava flows buried the nearby town of Cagsawa. — with report from AFP