QUEZON CITY (PIA) – The Philippine Institute of Volcanology and Seismology (Phivolcs) continues its close monitoring of volcanoes, particularly Mayon in Albay, Taal in Batangas and Pinatubo in Central Luzon, for possible lahar flow due to heavy rains brought by Super Typhoon Pepito (Man-yi).
In its earlier Lahar advisory for monitored volcanoes to be affected by Typhoon Pepito issued on Nov. 15 at 8:00 PM, the state volcanologist said the typhoon “can be expected to generate volcanic sediment flows or lahars, muddy streamflows or muddy run-off in rivers and drainage areas on the monitored active volcanoes of Mayon, Pinatubo and Taal.”
On Nov. 17, it noted in its Mayon Volcano Summary of 24Hr Observation the following warning:
“Possible hazards that can occur:
-Sudden steam-driven or phreatic eruptions
-Rockfalls or landslides/avalanches
-Lahars during heavy and prolonged rainfall17 November 2024 12:00 AM”
Alert Level 1 is maintained over Mayon, as Phivolcs recommends against entry into the volcano’s 6-kilometer radius Permanent Danger Zone (PDZ) as well as flying any aircraft close to the volcano.
Phivolcs earlier said, “Prolonged intense to torrential rainfall may generate post-eruption lahars on major channels draining Mayon Volcano by incorporating loose material from remnant pyroclastic density current (PDC) deposits from the January-March 2018 eruption. The bulk of erodible PDC deposits occupy the watershed areas of the Miisi, Mabinit, Buyuan and Basud Channels. In addition, older and erodible eruption deposits that occupy the watershed areas on the eastern and western slopes of the edifice and can be remobilized as non-eruption lahars by erosion of banks and channel beds. Mayon lahars can threaten communities downstream of the above channels with inundation, burial and wash away. Potential lahars and sediment-laden streamflows may occur along the Miisi, Binaan, Anoling, Quirangay, Maninila, Masarawag, Muladbucad, Nasisi, Mabinit, Matanag, Basud and Bulawan Channels in Albay Province.”
For Pinatubo, which is located on the tripoint of Zambales, Tarlac and Pampanga provinces in Central Luzon, Phivolcs said, “Prolonged and heavy rainfall may generate non-eruption lahars on major rivers draining western Pinatubo Volcano where significant deposits of the 1991 PDCs remain on the watershed. Pinatubo lahars are likely be channel-confined and occur on the upper to middle reaches of the Sto. Tomas- Marella and Bucao River systems but may transition to muddy streamflows and floods on the lower reaches and affect adjacent communities of San Marcelino, San Narciso, San Felipe and Botolan, Zambales Province. Muddy streamflows may likewise be generated along the O’Donnell and Pasig-Potrero River systems draining the Pinatubo edifice to the north and southeast, respectively and affect downstream communities in Tarlac and Pampanga Provinces.”
For Taal, it said, “Prolonged and heavy rainfall may also generate muddy streamflow, muddy runoff and even volcanic debris flows around Taal Volcano, particularly on the slopes west and north of Taal Lake. Old and loose volcanic deposits, already saturated from previous rains, may be remobilized in streams, roads and across the lakeward slopes. In particular, muddy and debris flows can recur on previously affected communities of Agoncillo, Laurel and Talisay, Batangas Province.”
Phivolcs has aired strong recommendation for increased vigilance and readiness of communities and local government units (LGUs) in pre-determined zones of lahar and related hazards on the volcanoes. (PIA DMD)
