Emmanuel G. Ramos
Philippine Institute of Volcanology and
Seismology
ABSTRACT
Digital processing and analysis of
topographic data reveal details on the
structures of Taal Volcano Island. The
principles in spectral analysis were
used to process the digital topographic
data of Taal. The position and form of
the various volcanic units were
recognized through the deconvolution of
the digital elevation model into
wavelength components. Similar to the
concept of spectral analysis in
geophysics, the geomorphic filters used
on the digital elevation model allow the
visual identification of volcanic
landforms. In many cases, the existence
of nested cones and craters appear in
filtered terrain maps while in some
parts of the island, buried craters are
revealed. The sequence in the
development of the main crater through a
series of explosions that occurred in
1911 can also be reconstructed, even if
the processing was done on two data
sources with different levels of detail.
One is a 1:10,000 scale topographic map,
and the other from a 1988 bathymetric
map. Other features revealed by the
geomorphic filtering procedure are
faults and some subsidence-related
fissures formed early during the 1965
eruption sequence, despite these being
covered by tephra from subsequent
eruptive events. The result of the
digital analysis of topographic data is
a refined geologic map of Taal Volcano.
Geological
Society of the Philippines
Unit
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Pioneer Street, Mandaluyong City, Philippines