Collaborative Research: Closing the Loop on Lava Flow Models: Linking Thermal and Mechanical Controls on Flow Emplacement Dynamics Using Novel Field and Experimental Techniques

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The considerable hazard to property and infrastructure posed by effusive lava flows in volcanically active areas motivates this project to understand the physics of lava flow emplacement and improve our ability to predict their behavior. A fundamental control on the dynamics of lava flows arises from their rheology, which changes from fluid-like on eruption to solid-like during emplacement. This complex behavior has been investigated by accounting for either the mechanical or thermal evolution of a flow, but rarely have these approaches been coupled. This proposed work aims to link these two parallel approaches by developing new methods for quantifying lava flow morphology, which records the coupled thermal and mechanical evolution of the lava. It is proposed to use airborne- and ground-based laser mapping techniques to construct high-resolution (from 1 cm to ~1m) topographic maps with which we can resolve such features as individual clasts on lava surfaces to lava channels/levees and flow margins. Morphology observations will be coupled with laboratory measurements of the physical properties of the lava and physical experiments using analog materials that simulate lava flow behavior. The integrated experimental and observational will be used to test and refine predictive models of flow emplacement. Fieldwork will be conducted at two locations: Mauna Loa Volcano and the Oregon Cascades. These sites provide a range of initial lava compositions and eruption styles, making the results widely applicable to volcanically active areas globally. During emplacement, lava flows develop viscous and visco-elastic rheologies that, coupled with a solidifying crust, produce complex responses to deformation. For this reason, models of flow emplacement must consider both the mechanical and the thermal history of a flow. Mechanical models include gravitational spreading of viscous and Bingham yield strength fluids. Thermal models of have focused on basaltic lava channels, specifically on the reduction of flow cooling rates with increasing coverage of a solid surface, while the role of solidification on flow dynamics has been examined by determining tensional failure criteria of that solid crust. Until recently, models that link thermal and dynamical regimes have been limited to low Reynolds number (low flux) flow in radial spreading regimes. Over the past few years the team has extended laboratory experiments to examine solidifying flows at higher fluxes traveling through uniform and irregular channels. At the same time, we have obtained detailed data on distributions of flow surface morphologies, transport conditions, and material properties of basaltic lava produced by several recent eruptions. The proposed work will utilize airborne and ground-based LiDAR to make quantitative and comprehensive measurements of flow features and surface morphologies. It is expected that these data will lead to the development of surface analysis techniques that may have broad application within the Earth Sciences. They will use data to examine down-flow evolution of flow features such as: flow thickening and spreading, channel development, and solid crust thickening. Sampling of the same flows will allow the evaluation of thermal and rheological evolution as it relates to morphological changes. It is further proposed to evaluate current theoretical models (both mechanical and thermal) and identify their strengths and weaknesses. Based on these results, the team will conduct laboratory experiments to help address gaps in our understanding. Ultimately, this work will help unify the disparate approaches that have been taken to understand the physical processes of lava flow emplacement, improving our ability to both predict the behavior of active lava flows and learn about past volcanic activity that is recorded in solidified lava flows.