Insights into volcano degradation from analogue modelling: how volcano shape and size influence runoff erosion and morphology

Composite volcanoes have diverse morphologies due to their inextricably intertwined eruption, intrusion, and degradation histories. Surface runoff, a major erosional process involved in volcanic degradation, is dominantly controlled by climatic, lithologic, and topographic factors. Analogue models offer the opportunity to examine rainfall-induced erosion on a scaled volcano cone with the advantage of a well-constrained initial shape, homongenous lithology and controlled precipitation. In this study, we aim to document the morphological evolution and quantify eroded volumes and rates on variously-shaped analogue volcanic cones.

The experiments were carried out at the VUB volcanology analogue laboratory. Analogue volcanic landscapes were built from a combination of granular material consisting of silica sand, silica flour and kaolin. Cone shapes were scaled based on simplified measurements (height, base width, and slope angle) of natural pristine composite volcanoes; cones both with and without summit craters were analysed. Rainfall-induced erosion was simulated with four atomizer sprinklers. Using four DSLR cameras, photogrammetry-derived digital elevation models with sub-millimetre spatial resolutions were computed at regular time intervals during the experiments, allowing to estimate volume loss, which was compared to the measured sediment yield. Morphometric and drainage parameters of the eroding cones were then obtained with the automated MorVolc and DrainageVolc algorithms, previously used on natural volcanoes.

The resulting drainage network and morphological features of the analogue models mimic those occurring at natural volcanoes with different ages and climatic settings. Our results emphasize the importance of the initial cone morphometry on its subsequent morphological evolution by degradation processes. The next step will be to compare the main morphometric evolution with what is observed on natural volcanoes.