The Philippine Institute of Volcanology and Seismology (Phivolcs) on Sunday, Dec. 15 reiterated its warning that lahar could occur around Kanlaon Volcano due to the possibility of heavy rainfall.

The public is advised to avoid rivers, waterways, and areas downstream of the volcano, and to evacuate as instructed by authorities to ensure safety.

“Evacuate as advised by authorities. Let’s all be safe,” Phivolcs said.

Communities and local government units are urged to monitor weather conditions and rainfall warnings.

Avoid areas near rivers and waterways downstream of the volcano, and take preemptive evacuation measures if heavy rain develops.

Phivolcs said lahar, a secondary volcanic hazard from Kanlaon’s eruption, is a rapidly flowing mixture of volcanic material (ash and rocks) and water, typically triggered by heavy rainfall in river channels. It resembles a slurry of wet concrete, which can be thick and viscous (malapot/hagkot/lapuyot), or more diluted with water (malabnaw/lasyaw/lasaw).

Lahar may increase in volume as it erodes the landscape, carrying debris such as soil, rocks, plants, and structures.

It can also occur both during and after a volcanic eruption.

Phivolcs said the impacts of lahar include erosion and washout of river channels (erosion and washing away of soil, rocks, and other debris along river currents), burial of areas with mud (covering of affected areas with mud), and flooding in impacted areas (flooding in covered areas).

During the 24-hour monitoring period from Dec. 14 to 15, Phivolcs recorded 14 volcanic earthquakes and observed continuous moderate degassing of sulfur dioxide from the volcano.

Alert Level 3 (high level of unrest) remains in effect as volcanic activity continues, with the potential for more eruptions.