Report on Bulusan (Philippines) — February 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 2 (February 1980)
Managing Editor: David Squires.
Bulusan (Philippines) Ash explosions and earthquakes
Please cite this report as:
Global Volcanism Program, 1980. Report on Bulusan (Philippines) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 5:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198002-273010.
12.769°N, 124.056°E; summit elev. 1535 m
All times are local (unless otherwise noted)
The eruption continued with a second explosion on 12 January at 1640. Ash rose about 500 m above the crater rim, then drifted NNW. COMVOL had predicted further activity in the Bulusan Volcano Bulletin dated 4 January, based on patterns exhibited during previous eruptions, especially the 1878 eruption.
Citing a COMVOL official, Kyodo radio reported that a third explosion occurred on 7 February, apparently ejecting ash to 6 km. Ash emission was continuing early the next day. Residents left the area, reportedly because of 28 volcanic earthquakes and two tectonic events.
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.
Information Contacts: O. Peña, COMVOL, Quezon City; Kyodo Radio, Tokyo.