FLOWGO: a kinematic thermo-rheological model for lava flowing in a channel

Abstract.

We present a kinematic, self-adaptive, numerical model to describe the down-flow thermal and rheological evolution of channel-contained lava. As our control volume of lava advances down a channel it cools and crystallizes, an increasingly thick and extensive surface crust grows, and its heat budget and rheology evolve. By estimating down-flow heat and velocity loss, our model calculates the point at which the control volume becomes stationary, giving the maximum distance lava flowing in the channel can extend. Modeled effusion rates, velocities, widths, surface crust parameters, heat budget, cooling, temperature, crystallinity, viscosity, and yield strength all compare well with field data collected during eruptions at Mauna Loa, Kĩlauea, and Etna. Modeled lengths of 25–27, 2.5–5.7, and 0.59–0.83 km compare with measured lengths of 25–27, 4, and 0.75 km for the three flows, respectively. Over proximal flow portions we calculate cooling, crystallization, viscosity, and yield strength of 1–10°C km^–1, 0.001–0.01 volume fraction km^–1, 10³–10⁴ Pa s, and 10^–3–10² Pa, respectively. At the flow front, cooling, crystallization, viscosity, and yield strength increase to >100°C km^–1, 0.1 volume fraction km^–1, 10⁶–10⁷ Pa s, and 10³–10⁴ Pa, respectively, all of which combine to cause the lava to stop flowing. Our model presents a means of (a) analyzing lava flow thermo-rheological relationships; (b) identifying important factors in determining how far a channel-fed flow can extend; (c) assessing lava flow hazard; and (d) reconstructing flow regimes at prehistoric, unobserved, or remote flows.