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The dynamics of effusive events is controlled by the interplay between conduit geometry and source conditions. Dyke-like geometries have been traditionally assumed for describing conduits during effusive eruptions, but their depth-dependent and temporal modifications are largely unknown. We present a novel model which describes the evolution of conduit geometry during effusive eruptions by using a quasi steady state approach based on a 1-D conduit model and appropriate criteria for describing fluid shear stress and elastic deformation. This approach provides time-dependent trends for effusion rate, conduit geometry, exit velocity, and gas flow. Fluid shear stress leads to upward widening conduits, whereas elastic deformation becomes relevant only during final phases of effusive eruptions. Simulations can reproduce different trends of effusion rate, showing the effect of magma source conditions and country rock properties on the eruptive dynamics. This model can be potentially applied for data inversion in order to study specific case studies.

Plain Language Summary The dynamics of effusive eruptions is controlled by the interplay between the feeding conduit geometry and magma chamber conditions. Dyke-like geometries have been traditionally assumed for describing conduits of effusive eruptions, but their depth-dependent and temporal modifications are largely unknown. Conduit geometry is controlled by fluid shear stress and pressure-driven elastic deformation, which depend on magma and host rock properties. Here we present a novel model for studying the temporal evolution of effusive eruptions, using a steady-state conduit model and appropriate criteria for describing the temporal evolution of conduit geometry. Model inputs are related to host rock properties, magma source conditions, and some additional equations for describing the ascending magma behavior. The model provides time-dependent trends for effusion rate, conduit geometry, exit velocity, and gas flow. Because of the typical magma viscosity and velocity profiles along the conduit, they tend to produce higher erosion rates near the vent, giving place to upward widening conduits. Simulations are compatible with the erosion rates estimated for natural cases and are able to reproduce different curves of effusion rate. This model can be potentially applied for data inversion in order to study magma reservoir dynamics and conduit geometry evolution during specific case studies.