Processing of digital topography enables the recognition of several geomorphic units otherwise difficult to detect on Mariveles Volcano, Bataan. We have explored the principle that the topographic expression of geology results from the convolution of large-scale geologic features/processes with smaller scale processes that also modify the landform. This principle allows us to deconvolve the topography into various spatio-spectral signatures: the long wavelength and large amplitude topographic features are likely associated with the major geologic processes while the short wavelength and low amplitude components as likely representations of the more recent or smaller scale geologic processes. A series of spatial mapping filters were then developed based on this principle of convolution.

Mariveles Volcano was chosen as a test area for testing the procedure because of the relatively old topography of the site. The volcano’s landforms can be associated with various volcanic processes that are not readily discernible from regular topographic analysis. The stratovolcano is composed of lava and pyroclastic flows, with debris flows and alluvial deposits on its lower slopes. The volcano hosts a 2-km wide summit crater that is breached to the north, possibly along a large fault. Its slopes are currently densely vegetated and show moderately advanced state of erosion. Two satellite cones are present on its flanks, whose units blend with the slopes of the larger volcano. 3D rendering of the volcano’s digital topography enhances the appreciation of the general features of the terrain but leaves much to be desired for visually separating volcanic units from one another.

The spatial mapping filters we have devised enhanced the recognition of several geomorphic features of the volcano. The difference in relative age of the eastern and western slopes of the volcano is revealed by the results. Likewise, the possible synchronous eruptions of Mariveles with its two satellite cones are indicated by the presence of possible post-parasitic flows from the main volcano. The presence of another satellite cone to the south is also highlighted by the resulting maps. The existence of three well-defined pyroclastic fans on the eastern flank of the volcano is also revealed, and their relatively less-intense degree of erosion suggests these to be the latest major deposits from Mariveles’ eruptions. The presence and possible alignment of faults are also suggested by the low-amplitude, shot-wavelength components of the topography.

The features derived by employing the geomorphic deconvolution procedures we describe should help geologists delineate extent of deposits and lead them as they scout for structures on the ground and from topographic and remote sensing data. Based on our experience with Mariveles and Taal Volcanoes, we envision these geomorphic deconvolution procedures to be applicable in areas with rock units and structures that extend to a few kilometers in one dimension, and where recognition may be obscured by recent erosional and faulting processes.