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Report on Bulusan (Philippines) — 17 January-23 January 2024


Bulusan

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 17 January-23 January 2024
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2024. Report on Bulusan (Philippines) (Sennert, S, ed.). Weekly Volcanic Activity Report, 17 January-23 January 2024. Smithsonian Institution and US Geological Survey.

Weekly Report (17 January-23 January 2024)

Bulusan

Philippines

12.769°N, 124.056°E; summit elev. 1535 m

All times are local (unless otherwise noted)


PHIVOLCS reported increased seismicity at Bulusan in a special advisory. The seismic network recorded a total of 91 volcanic-tectonic earthquakes, associated with rock fracturing, located at depths of 2-4 km beneath the SW flank from 0138 on 22 January to 0130 on 23 January. Gas emissions characterized as weak-to-moderate rose from the summit crater and active vents. Both the SE and SW flanks have been inflated since February 2023 based on ground deformation data from continuous GPS and electronic tilt monitoring. The Alert Level remained at 1 (the second level on a scale of 0-5) and PHIVOLCS reminded the public 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)