Geologic Background:
Bulusan is located 280 km NNE of Canlaon and 70
km SSE of Mayon volcano. Luzon's southernmost volcano,
Bulusan, was constructed within the 11-km-diameter Irosin
caldera, which was formed more than 36,000 years ago. A
broad, flat moat is located below the prominent SW
caldera rim; the NE rim is buried by the Bulusan complex.
Bulusan is flanked by several other large lava domes and
cones that were constructed within the caldera, including
the prominent Mount Jormajan lava dome on the SW flank
and Sharp Peak to the NE. The summit of the volcano 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.
Historic Activity:
- Moderate explosive eruptions have been recorded since
1852.
- Between May 1918 and May 1922 there were 17
explosive, ash-producing eruptions, a lava flow, possible
dome growth, and nuees ardentes.
- Intermittent explosions during 1978-83 prompted some
evacuations.
Recent Activity:
- In April 1981 following an 8-day earthquake swarm
several explosions ejected tephra clouds that reached 8
km in height.
- In late June 1983 mild phreatic explosions occurred
from the summit crater with eruption clouds reaching 1200
m.
- During 1985 to early 1987 several seismic swarms have
been recorded and strong volcanic earthquakes have
occurred from late October to early December 1987.
- Small ash eruptions occurred in February and March
1988. High level of seismicity from April to August
1988.
- A series of phreatic eruptions began on Nov. 27, 1994
and continued through Jan. 28, 1995. Eruptive column
reached heights of as much as 3 km and spread ash upto 16
km away.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 8, No. 6 to V. 13,
No. 8)
- Global Volcanism Network (V. 19, No. 11 to V. 20, No.
1).
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