A dynamic study of caldera collapse: Insights from analogue models and geophysical data

Caldera collapse dynamics result from complex interactions involving multiple parameters, affecting surface deformation style, internal structural development, and structural style transitions. Furthermore, calderas are not only prominent features in volcanic environments, bearing intrinsic scientific significance, but they also represent a primary source of risk during periods of unrest, as well as a critical target for geo-resources (e.g., geothermal energy). For these reasons, understanding caldera collapse dynamics is of paramount importance for risk assessment and mitigation, as well as for understanding the evolution of volcano-tectonic systems.

We investigate caldera collapse dynamics through controlled laboratory experiments. Collapse is simulated in a granular material by draining an analogue magma (Polyglycerine-3) from an analogue magma chamber, with dynamic parameters (e.g., pressure) monitored using laboratory-scale geophysical sensors. The coupling between “classical” analysis (i.e., photogrammetric reconstruction of the model surface to quantify 3D deformation, structural line drawing, and PIV analysis) and geophysical data allows for the identification of a critical transition between inverse and normal faulting within the granular volume. While the magma discharge process maintains a consistent flow rate, overall fault propagation is influenced by this transition, leading to variations in caldera morphology. Our findings suggest that the evolving stress field significantly impacts faulting behavior, revealing the intricate relationship between internal fault mechanisms and surface collapse. This may provide a new way to compare analogue data with natural systems and enhances our understanding of caldera collapse dynamics, offering valuable insights into similar phenomena in volcanic environments.