Bulusan volcano alert level raised, Philippines

Bulusan volcano alert level raised, Philippines

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level of Bulusan Volcano, the southernmost volcano on Luzon Island in the Republic of the Philippines, from Alert Level 0 (normal) to Alert Level 1 (abnormal). The local government units and the public are strictly reminded that entry into the 4-kilometer (2.5 miles) radius Permanent Danger Zone (PDZ) should be avoided.

An increase in seismic activity of Bulusan volcano was detected from May 4 to 5, 2019, with a total of sixteen volcanic earthquakes recorded by the seismic monitoring network. Tilt data from April 29 to May 5, 2019, indicated slight inflation of the upper slopes.

There is also a notable increase in water temperature of the monitored hot springs while wispy to weak emission of white steam plumes was observed from the southeast vents.

Local authorities around the Bulusan were advised to enforce the 4-kilometer (2.5 miles) radius Permanent Danger Zone (PDZ).

But on the southern slopes of the volcano, an Extended Danger Zone (EDZ) 2 km further downslope from the PDZ should be off limits of residents and visitors because of the possibility of sudden and hazardous phreatic eruptions, rockfall, and landslides, Solidum added.

Civil aviation authorities must also advise pilots to avoid flying close to the volcano's summit as ask from any sudden phreatic eruption can be hazardous to aircraft.

Furthermore, people living within valleys and along river/stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall. DOST-PHILVOCS is closely monitoring Bulusan volcano's condition and any new development will be relayed to all concerned.

The last eruption of this volcano took place on June 5, 2017 (VEI 1).

Geological summary

Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter (6.8 miles) dacitic-to-rhyolitic Irosin caldera, which was formed about 36 000 years ago. Bulusan 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 Bulusan 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 of 1 565-m-high (5 134  feet) Bulusan volcano is unvegetated and contains a 300-m-wide (984 feet), 50-m-deep (164 feet) crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century. (GVP)

Featured image credit: Chris Newhall (U.S. Geological Survey).

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