Mayon volcano. Photo courtesy of Camalig Information Office.
Ashfall from recent activity at Mayon Volcano has affected thousands of residents in the Bicol region, according to government data.
The Office of Civil Defense (OCD) reported that as of May 4, some 30,522 families, or 102,406 individuals, across 87 barangays were impacted by the volcanic event.
The Philippine Space Agency (PhilSA) said ash deposits spread widely following a pyroclastic density current observed on May 2.
In its released map, PhilSA estimated that at least 8,544 hectares were covered by ash, an area roughly half the size of Quezon City.
Pyroclastic density currents are fast-moving flows of hot gas, ash, and rock fragments that descend from a volcano during eruptive episodes.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said ashfall consists of fine volcanic particles smaller than 2 millimeters and poses risks to public health.
It added that ash can also endanger aircraft and damage equipment used in transportation and power generation.
The United States Geological Survey said ashfall, even in thin layers, can disrupt buildings, transportation systems, water and wastewater services, power supply, communications, and agriculture.