At 9:12 AM, 21 February 2011, an explosion occurred at Bulusan Volcano (12=B046.2'N, 124=B003'E). This event was recorded as explosion type earthquake lasting for about nineteen (19) minutes and was accompanied by a rumbling sound which was heard up to ten (10) kilometres away from Juban, Sorsogon. The explosion produced a greyish ash column that rose to a height of about three (3) kilometres above the summit before drifting to the southwest. Preliminary field investigation confirmed the presence of ash deposit in Barangay Monbon and Irosin proper in Irosin, Sorsogon.
Alert Level 1 remains hoisted over Bulusan Volcano.
1. The public is strongly advised not to enter inside the 4-kilometer radius Permanent Danger Zone (PDZ) as it may be affected by sudden steam explosions.
2. People residing near valleys and streams are also strongly advised to be vigilant against sediment-laden stream flows in the event of heavy and continuous rainfall.
3. Due to the prevailing wind direction, residents located in the northwest and southwest sectors of the volcano are advised to take precautions against ashfalls.
4. Civil aviation authorities must advise pilots to avoid flying close to the volcano's summit as ejected ash and volcanic fragments from sudden explosions may pose hazards to aircrafts.