Caldera collapse triggered by central vent eruptions - A numerical study

The onset of large caldera forming eruptions is commonly associated with pre-, syn- and post-collapse volcanism along the previously formed ring faults. This collapse mechanism results on a caldera that spans the entire extent of the magma chamber as the ring faults are thought to localise at the margins of the chamber. Whilst larger calderas have been extensively researched, with numerical models providing a robust understanding of the driving forces, smaller systems (≤ 5 km in diameter) can also produce caldera-forming eruptions. Prominent examples include Krakatau (Indonesia) and Crater Lake (USA). Pre- and post-collapse volcanism is typically associated with a central vent eruption at a volcanic edifice.In this study, we employ the thermo-mechanical geodynamic code JustRelax.jl to investigate the mechanics behind central vent eruptions that trigger caldera collapses. The models use a non-linear visco-elasto-viscoplastic rheology, magma dynamics of a pre-existing shallow magma chamber of various geometry, far-field tectonic stresses and a central conduit structure that connects the magma chamber with a volcanic edifice. We utilise a dynamic conduit density parametrisation that accounts for the nucleation of bubbles when the magma rises to the surface through a gas solubility constant and total volatile content. The dynamic conduit density parametrisation facilitates the emulation of magma upward flow and progressive chamber depletion. This framework enables investigation into the governing underlying processes of central vent-driven caldera formation. We present a systematic parameter study on the driving forces behind this type of caldera collapse.