DEM-based morphometry as a tool for reconstructing primary volcanic landforms: examples from the Bِrzsِny Mountains, Hungary

A complex application of digital elevation model (DEM) derivatives is presented for a highly degraded volcanic area, the Miocene Bِrzsِny Mountains, Hungary. We propose unconventional geometrical and mathematical transformations of the original DEM data in order to enhance the topographic features of the volcanic relief that stem from the primary landforms. It is the actual ridges that represent the least degraded surfaces of an original, hypothetical volcanic cone. Therefore, the statistical DEM properties such as ridge pattern (1), slope angle distribution (2) and higher-order slope derivatives (3) should be strongly correlated with the paleosurface. Automated creation of a ridge pattern image is based on the local histogram of the DEM, and helps to outline the original surface remnants. A local slope angle histogram may point out structurally coherent parts of the original cone: for instance, tectonic displacements or large-scale sector slumping does not affect the slope angle histogram of the original relief. Evaluating the ridge maps and slope aspect maps of the Bِrzsِny Mountains allows various cone sectors to be identified and connected to the original volcano-structural elements. Finally, the polar coordinate-transformed (PCT) image (4) centered on a hypothesized eruptive vent enhances the original, radial valley pattern. In the case of multiple eruptive centers and/or post-eruptive tectonic modifications, the radial pattern is changed, which may be evidenced in the PCT image. In fact, the PCT image analysis for the Bِrzsِny Mountains suggests a complex post-eruptive tectonic scenario. The presented methods can be recommended to infer the original configuration of highly degraded volcanic structures with poorly known tectonic and erosional history.