The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing unrest at Bulusan during 30 April-5 May. The seismic network recorded 50-127 daily volcanic earthquakes, including 2-52 periods of volcanic tremor during 30 April-3 May that each lasted 1-58 minutes. Gas-and-steam emissions of variable densities rose as high has 500 m above the summit and drifted E, WNW, W, and WSW; views were obscured on 2 May. Daily averages of sulfur dioxide emissions ranged from 809 to 2,131 tonnes per day. The Alert Level remained at 1 (the second lowest level on a scale of 0-5). The public was reminded not to enter the 4-km-radius Permanent Danger Zone (PDZ) and to be vigilant within the 2-km Extended Danger Zone (EDZ) on the SE flank.

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)