Dam-break Experiments of Particle- and Bubble-bearing Suspensions for Understanding Lava Flow Rheology

Lava rheology exerts a leading order control on flow emplacement, and quantitative expressions to describe lava rheology are an essential component of predictive models of lava flow advance and emplacement. The viscosity of lava can vary over orders of magnitude, even within a single flow, and is highly sensitive to the presence of solid particles and gas bubbles. In particular, the effect of bubbles on the rheology two- and three-phase suspensions remains an outstanding challenge in volcano science. Analogue experiments afford the opportunity to investigate a broad range of crystal and bubble contents that are relevant to natural magmatic systems.

We utilize a dam-break consistometer setup to determine the rheology of particle- and bubble-bearing suspensions based on viscous corn syrup. We use neutrally buoyant, angular particles, and investigate both nearly monodisperse and polydisperse particle size populations up to ~40% by volume. We use a chemical reaction between baking soda and citric acid to generate high volume fractions of gas bubbles (up to ~70%) with polydisperse size populations similar to those observed in natural samples. We choose our conditions to match those likely experienced by the Fissure 8 channelized flow of the 2018 Kilauea eruption. To infer rheological parameters for the experimental flows, we utilize numerical simulations to fit a Herschel-Bulkley rheological model to the experiments. Our results allow us to develop parameterizations for the effect of bubbles and combined particle-bubble populations on lava rheology.