Legazpi: The Philippine Institute of Volcanology and Seismology (Phivolcs) on Monday issued a warning about the possibility of volcanic sediment flows, known as lahars, from Mayon Volcano due to the forecast of heavy rains across the Bicol Region.

According to Philippines News Agency, the anticipated rains, brought on by Tropical Depression Verbena and the shear line, could lead to muddy streamflows or muddy run-off in rivers and drainage areas. Phivolcs has urged increased vigilance, readiness, and if necessary, the pre-emptive evacuation of communities in designated lahar-prone zones in Albay province.

Intense to torrential rainfall has the potential to generate dangerous post-eruption lahars in major channels draining Mayon Volcano. This occurs by eroding loose material from the pyroclastic deposits left by the 2018 and 2023 eruptions. The bulk of these erodible deposits is located in the watershed areas of Miisi, Binaan, Mabinit, Buyuan, Anoling, Matanag, Bonga, and Basud Channels. Communities along and downstream of these channels face a significant threat from post-eruption lahars.

Older pyroclastic deposits on the southwestern slopes, which have been continuously eroded by intense rains through the Masarawag and Maninila Channels, pose a risk of non-eruption lahars that could impact communities in Guinobatan. Phivolcs advises local communities and government units in these areas to monitor rainfall conditions closely and take pre-emptive measures to ensure safety.

Phivolcs emphasized that Mayon lahars have historically threatened communities with their force of impact, inundation, burial, and potential to wash out to sea, owing to their capacity to transport large volumes of gravel and boulders.