Long-term erosion dynamics and morphological evolution of composite volcanoes: Insights from analogue modelling

Volcanoes undergo rapid growth and extended periods of repose during which erosion dominates, representing natural laboratories for studying erosion patterns and rates across various timescales. However, complex constructional and degradational histories and limited temporal constraints make analyzing volcano erosion dynamics challenging. Analogue models with rainfall-induced runoff offer a simplified and controlled setting to explore volcanic erosion processes and evolution with well-constrained initial cone geometries. This study documents the morphological evolution of analogue volcanoes during rainfall simulation experiments, scaled to reflect natural pristine composite volcanoes. Different cone types, with varied slope profiles and summit craters, are analyzed using photogrammetry-derived digital elevation models with sub-millimeter resolution. Using these models, we quantify the evolution of morphometric parameters, including cone and drainage basin geometries, denudation and erosion rates. Most morphometric parameters and erosion rates show rapid initial variations, followed by more gradual trends. As erosion progresses, the hypsometric integral decreases for cones with initial linear slope profiles and increases for those with concave slopes, highlighting the importance of initial slope profiles in interpreting degrees of erosion. The presence of a summit crater introduces unique erosional processes, shaping wider basins during an initial erosional phase. All cone types develop towards a geometric equilibrium state where the initial diverse morphometric values converge for the hypsometry integral, drainage density, and irregularity index. Initial slope profile and the presence of a summit crater do not significantly affect the topography of the final erosional phase, underscoring the concept of equifinality. These analogue experiments enhance our understanding of real-world volcanic landscape evolution.