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

火山活跃地区的熔岩流对财产和基础设施造成了相当大的危害，这促使该项目了解熔岩流就位的物理原理，并提高我们预测其行为的能力。控制熔岩流动动力学的一个基本因素是其流变性，即熔岩在喷发时呈流体状，在就位时呈固体状。这种复杂的行为已经通过计算流动的机械或热演化来研究，但很少将这些方法结合起来。本研究旨在通过发展量化熔岩流形态的新方法，将这两种平行的方法联系起来，这些方法记录了熔岩的热学和力学耦合演化。建议利用机载和地面激光测绘技术构建高分辨率地形图（从1cm到~1m），我们可以利用这些地形图来解析熔岩表面的单个碎屑到熔岩通道/堤防和流缘等特征。形态学观察将与熔岩物理性质的实验室测量相结合，并使用模拟熔岩流动行为的模拟材料进行物理实验。综合实验和观测将用于测试和完善流动就位的预测模型。实地考察将在两个地点进行：莫纳罗亚火山和俄勒冈瀑布。这些地点提供了一系列初始熔岩成分和喷发风格，使结果广泛适用于全球火山活跃地区。在就位过程中，熔岩流形成粘性和粘弹性流变，再加上固化的地壳，产生复杂的变形响应。因此，流动就位模型必须同时考虑流动的力学历史和热历史。力学模型包括粘性流体和Bingham屈服强度流体的重力扩展。热模型集中在玄武岩熔岩通道上，特别是随着固体表面覆盖范围的增加流动冷却速率的降低，而凝固对流动动力学的作用已经通过确定固体地壳的张拉破坏标准进行了检查。直到最近，将热流和动力流联系起来的模型还局限于低雷诺数（低通量）径向扩散流。在过去的几年里，该团队扩展了实验室实验，以检查在均匀和不规则通道中流动的高通量凝固流。同时，我们获得了最近几次喷发产生的玄武岩熔岩流面形态分布、输送条件和物质性质的详细数据。拟议的工作将利用机载和地面激光雷达对流动特征和表面形态进行定量和全面的测量。预计这些数据将导致表面分析技术的发展，可能在地球科学中有广泛的应用。他们将使用数据来检查流动特征的下流演化，如：流动增厚和扩展、通道发育和固体地壳增厚。取样相同的流动将允许评估热和流变演变，因为它涉及到形态变化。进一步建议评估当前的理论模型（机械和热），并确定其优点和缺点。基于这些结果，该团队将进行实验室实验，以帮助解决我们在理解上的差距。最终，这项工作将有助于统一已经采取的不同方法来理解熔岩流就位的物理过程，提高我们预测活跃熔岩流行为和了解凝固熔岩流中记录的过去火山活动的能力。

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.