Shoreline-crossing geomorphology of instable volcanic islands from a quantitative DEM analysis

Volcanic islands are known to be a source of many natural hazards associated with active volcanism. The processes leading to the instability of their flanks, however are less well understood. The movement of an instable volcanic flank occurs in either or both of two ways; slow sliding of several cm per year (i.e. Etna, Italy) and/or the catastrophic collapse of a large portion of the edifice (i.e. Anak Krakatau, Indonesia). The conditions and precursors leading to such events are often unknown.

The limited availability of high-resolution bathymetry data especially at the coast is often restricting the quantitative geomorphological investigation to the subaerial part of the volcanic island. It is essential, however, to include the entire volcanic edifice as instability affects the volcano from summit to seafloor. In this study, we test whether and in which way, the morphology of the volcanic edifice affects its instability.

We therefore combine openly available high-resolution bathymetric and topographic grids (50-150m grid spacing) to create shoreline-crossing DEMs of more than 25 volcanic islands in four areas (archipelagos of Hawaii, Canaries, Mariana Islands and South Sandwich Islands). Additionally, we define sections of equal angle (flanks) with the summit as the central point. Morphological parameters, such as area, volume, height from seafloor, slope etc. of both the entire volcano and each of the 8 flanks, respectively are derived from the DEM grids and inserted into a database. The statistical analysis of this data combined with the history of flank failure will shed light on the influence the morphology of a volcanic island has on its instability. This will lead to a better understanding of the processes involved in the movement of instable volcanic flanks.