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

火山活动区喷出的熔岩流对财产和基础设施构成相当大的危险，这促使该项目了解熔岩流侵位的物理学，并提高我们预测它们行为的能力。对熔岩流动动力学的基本控制来自于它们的流变性，从喷发时的类液体变化到侵位时的类固体。这种复杂的行为已经通过考虑流动的机械或热演化来研究，但很少有这些方法结合在一起。这项拟议的工作旨在通过开发新的方法来量化熔岩流形态，从而将这两种平行的方法联系起来，该方法记录了熔岩的热和机械耦合演化。建议使用机载和地面激光测绘技术来绘制高分辨率(从1 cm到~1m)地形图，利用这些地形图可以分辨熔岩表面的单个碎屑到熔岩通道/堤坝和水流边缘等特征。形态观察将与熔岩物理性质的实验室测量和使用模拟熔岩流动行为的模拟材料的物理实验相结合。实验和观测相结合的方法将用于检验和改进流动侵位的预测模型。实地考察将在两个地点进行：莫纳罗亚火山和俄勒冈瀑布。这些遗址提供了一系列初始熔岩成分和喷发方式，使这些结果广泛适用于全球火山活跃地区。在侵位过程中，熔岩流发展出粘性和粘弹性流变性，与凝固的地壳相结合，对变形产生复杂的反应。因此，流动侵位模型必须同时考虑流动的机械历史和热历史。力学模型包括粘性流体和宾汉屈服强度流体的重力扩散。的热模型侧重于玄武岩熔岩通道，特别是随着固体表面覆盖率的增加而降低流动冷却速度，而凝固对流动动力学的作用已通过确定该固体地壳的拉伸破坏准则来检验。直到最近，将热力和动力状态联系起来的模型一直局限于径向扩展状态下的低雷诺数(低通量)流动。在过去的几年里，该团队扩大了实验室实验，以检查流经均匀和不规则通道的较高流量的凝固流动。同时，我们获得了最近几次喷发产生的玄武岩熔岩的流面形态分布、运移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貌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，这些技术可能在地球科学中有广泛的应用。他们将使用数据来研究水流特征的向下演变，例如：水流增厚和扩散、河道发育和固体地壳增厚。对相同流量的采样将允许评估与形态变化相关的热和流变性演变。进一步建议评估当前的理论模型(包括机械和热学模型)，并找出它们的优点和缺点。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采取的不同方法，以了解熔岩流侵位的物理过程，提高我们预测活动熔岩流行为和了解固化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.