The Effect of Bubbles On The Rheology Of Lava Flows: Insights From Large-Scale Two-Phase Experiments

Whereas it is well known that bubbles have a dramatic effect on lava rheology, their impact on lava flow behavior has not been extensively investigated yet. In order to quantify it, we conducted a series of large-scale two-phase (melt+bubbles) experiments at the Syracuse University Lava Project. We emplaced nine basaltic lava flows of varying bubble content in the low to intermediate range (approximately 10-50 vol%), measured their velocity through particle image velocimetry, and inferred their bulk viscosity through Jeffreys' equation. Melt-only viscosity was measured through concentric cylinder and parallel plate viscometry, allowing us to isolate the effect of bubbles on the viscosity of our experimental flows. Our results, which quantitatively assess the effect of bubbles on the rheology of basaltic lava flows, will provide the basis to refine multi-phase flow models, fundamental in order to deliver accurate lava flow emplacement forecasts.