Bulusan volcano (Philippines): phreatic explosions

New, sporadic explosions have occurred at the volcano since 1 May, ejecting small plumes of ash. PHILVOLCS raised the alert level to 1 and an exclusion zone of 4 km around the volcano is in place.
According to the monitoring volcanologists, the activity has been phreatic in origin, i.e. caused by overheated ground-water rather than fresh magma at the surface.
The first eruption was detected by its seismic signal and fine ash fall observed on the western and northwestern side of the volcano in the villages of Gulang-Gulang (6.5 km distance) and Sangjayron (11 km distance).
New ash emissions occurred last night. According to PHILVOLCS, an explosion from a vent on the northwestern slope of the volcano lasted 3:30 minutes and produced an ash plume that rose 250 m and drifted to the west. Ash falls occurred in the small town of Irosin, about 7.5 km southwest of the summit.
Authorities decided to evacuate the nearest villages, especially Cogon. More than 1,100 people were evacuated during the last hours and relocated to the building of the Gallanosa high school at Irosin.
For the time being, volcanologists do not think that a more intense eruptive phase is likely to follow, but that the volcano rather might undergo a phase of similar phreatic explosions until its hydrothermal system is again in equilibrium, a typical behavior of the volcano in the historic past. Eruptions last occurred in 2006-07 and 2010-11, sometimes producing quite large ash plumes.