Geologic Background:
Taal volcano is one of the most active
volcanoes in the Philippines and has produced some of its
most powerful historical eruptions. In contrast to Mayon
volcano, Taal is not topographically prominent, but its
prehistorical eruptions have greatly changed the
topography of SW Luzon. The 15 x 20 km Taal caldera is
largely filled by Lake Taal, whose 267 sq km surface lies
700 m below the south caldera rim and only 3 m above sea
level. The 5-km-wide Volcano Island in north-central Lake
Taal, the location of all historical eruptions, is a
complex volcano composed of coalescing small
stratovolcanoes, tuff rings, and scoria cones. Powerful
pyroclastic flows and surges from historical eruptions of
Taal have caused many fatalities.
Historic Activity:
- The historically active cone of Taal forms a small
inhabited island (Volcano Island) in a 15 x 22 km caldera
lake with a 6 km dia. caldera lake. Six of its 24 known
eruptions since 1572 have caused fatalities, many from
tsunamis in the lake.
- Frequent explosive activity followed a major eruption
in 1965 and continued through 1970.
- Preatic activity occurred again in 1976, and in
November 1977 built a small cone in the 1976 crater. All
activity occurred within the caldera which is filled with
a lake.
Recent Activity:
- Seismic activity began to increase on October 30,
1987 and ended by November 14. Thermal and steaming
conditions remained unchanged from normal levels but some
subsidence occurred along caldera lake shorelines.
Seismicity began to increase in July 1989 and epicenters
have migrated from 9 to 5 km deep from Aug 18 to Oct. 2.
Increased seismicity began in March and continues in
mid-August 1991. Earthquake swarm on Feb. 14-16, 1992
apparently accompanied a magma intrusion episode.
- Beginning in late February 1994, Taal stratovolcano
underwent increases in seismicity, deformation,
temperature, and other signs of growing instability.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 12, No. 10 to V. 14,
No. 10)
- Global Volcanism Network (V. 16, No. 3 to V. 19, No.
2).
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