Thermo‐Mechanical Controls on Central‐Vent Caldera Collapse

This is the authors' abstract. We don't add key points for this paper.

Large‐scale magmatic systems are associated with catastrophic caldera‐forming eruptions, posing hazards to millions near active volcanoes. Despite occurring across a range of sizes, the physics driving caldera collapse remain incompletely understood. While large calderas have received considerable attention, moderately sized calderas (∼5–10 km), such as Crater Lake (USA), attributed to central‐vent eruptions with volumes of 10–100 , remain comparatively understudied. We therefore developed a multi‐physics numerical modeling approach to investigate the mechanics of such collapses using the thermo‐mechanical code JustRelax.jl. Our 2D models couple magma dynamics, far‐field tectonic stresses, and non‐linear visco‐elasto‐viscoplastic rheologies for the crust and magma. Each model incorporates a thermally active, convecting magma chamber and surrounding mush, a volcanic edifice, melting and solidification of host rock, and a parametrization for magma recharge and eruption. Results show two distinct types of ring fault development: outward‐to‐subvertical faults nucleating at the surface and propagating downward, and radial faults originating at the chamber roof and propagating upward, with a transitional regime capable of evolving toward either type. Collapse dynamics range from structured, piston‐like subsidence to chaotic, non‐coherent roof block collapse. We find that the underpressure required for collapse onset scales logarithmically with the roof ratio and provide a scaling law that captures this behavior. Thermal weakening of the crust has a significant effect on eruption potential, shifting systems from a mass‐injection‐dominated to a non‐eruptive regime. Applied to natural calderas, our models reproduce key observational constraints including caldera diameter and erupted volumes, providing a novel thermo‐mechanical framework for understanding central‐vent caldera collapse.