At 1037 on 5 June a phreatic eruption at Bulusan produced a gray steam-rich plume, somewhat visible through weather cloud cover, that rose at least 1 km above the summit and drifted W. The event lasted about 17 minutes and was visible from Juban (Sorsogon Province). Ashfall was reported in Puting Sapa, Añog, Guruyan, Catanusan, Buraburan, Bacolod, and Sangkayon in Juban, and Bolos in Irosin, Sorsogon Province. Residents of Añog, Guruyan, and Catanusan also reported rumbling sounds and a sulfur odor. PHIVOLCS raised the Alert Level to 1 (on a scale of 0-5) and reminded the public not to enter the 4-km-radius Permanent Danger Zone (PDZ) nor the 2 km Extended Danger Zone (EDZ) on the SE flank. After the eruption gas emissions rose from the main crater and, for the first time this year, from the NW summit vent.

Geological Summary. Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)