2026 Birnbaum VENUSS Solidifying Lava FEM

The development of a solid rind or carapace at the surface of lava flows and domes results in a transition in deformation mechanism from dominantly viscous to elastic or plastic. This transition has a significant impact on the rate and style of emplacement, including on the construction of channelized flows, over-steepened margins, and flow advance due to lava breakouts. To address these important processes, particularly in subaqueous, subglacial, and extraterrestrial environments, we present a new numerical model, Viscous-Elastic Numerically Unified Solver for Solidifying flows (VENUSS), designed for cooling and solidifying free surface flows. The model effectively couples a viscous fluid interior with an elastic shell whose thickness increases in response to cooling. Our demonstration reveals that when a dome-like shape is fed from below and includes an elastic shell, it undergoes more lateral expansion and less vertical uplift compared to a similar high-viscosity rind. This indicates the essential role of lateral stress transfer in solid layers for accurate interpretation and prediction of dome deformation.