Report on Bulusan (Philippines) — 7 June-13 June 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 June-13 June 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Bulusan (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 June-13 June 2006. Smithsonian Institution and US Geological Survey.
12.769°N, 124.056°E; summit elev. 1535 m
All times are local (unless otherwise noted)
According to PHIVOLCS, an ash-and-steam cloud from Bulusan on 7 June reached a height of approximately 2 km above the summit (11,700 ft a.s.l.) and drifted N and NW. Light ashfall was reported 5 km N and trace amounts as far as 20 km N. The Alert Level was raised to 2 (scale 0 to 5), which means restricted entry within 4 km of the summit. On 10 June, an ash-and-steam cloud reached a height of ~1 km above the summit (8,400 ft a.s.l.) and drifted N and NE. A news article reported one death caused by an asthma attack from exposure to ash.
Geologic Background. 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.