Mount Bulusan’s full eruption can possibly affect the towns of Juban, Irosin, Casiguran, Gubat, Barcelona and Busulan covering around 70 barangays. These towns were covered by the Bulusan Volcano hazard zones established by Phivolcs. These barangays lie within the 4-10 km radius from the volcano’s summit.
Experts describe Mt. Bulusan as Luzon Island’s southernmost stratovolcano.
It is found in the province of Sorsogon in Bicol region, about 70 km southeast of world-famous Mayon Volcano and about 380 kilometers southeast of Manila, the Philippine capital.
The volcano forms part of the Bicol Volcanic Chain which stretches from Camarines Norte in the north to Sorsogon in the south.
According to experts, Mt. Bulusan is among the Philippines’ 22 most active volcanoes. Bulusan is the fourth most active volcano in the Philippines after Mayon in Albay, Taal in Batangas and Pinatubo in Zambales.
Mt. Bulusan is inside a caldera formed about 40,000 years ago. It rises 1,565 meters above sea level and has a base diameter of 15 km.
The volcano has four craters and four hot springs.
Crater No. 1 is called Blackbird Lake which is 20 meters in diameter and 15 meters deep.
The oval Crater No. 2 is 60 meters by 3 meters and 15 meters deep.
Crater No. 3 is about 90 meters in diameter and 20 meters deep.
The rim of Crater No. 4 near the northeastern area opened during the 1981 eruption.
A 100-meter fissure five to eight meters wide exists below Crater No. 4.
Mt. Bulusan’s hot springs are San Benon Springs, Mapaso Springs, San Vicente Springs and Masacrot Springs.
Volcanoes adjacent to Mt. Bulusan are Mt. Homahan, Mt. Binitacan, Mt. Batuan, Mt. Calungalan, Mt. Calaunan, Mt. Tabon-Tabon, Mt. Juban and Mt. Jormajan.
The 1,565-meter volcano erupted 15 times since monitoring began in 1886, the latest of which was during the July-October 2007 period.
The earliest recorded eruption of Bulusan Volcano was in 1852.
Mount Bulusan has been on Alert Level 1 since 2007, when the volcano last erupted on July 31 at approximately 9:37 a.m., spewing ash up to six kilometers high for about twenty minutes.
Ash fall covered the villages of Cogon, Gulang-Gulang, Bolos, Monbon and Gabao in Irosin town, and Puting Sapa, Sangkayon and Buraburan in Juban town, but there were no casualties, and no evacuation was necessary.