Active Lava Lakes as a Window into Magma and Volcano Dynamics

该项目的主要目的是促进我们对岩浆管道中的循环以及地下岩浆系统、地表和大气之间的相互作用和质量交换的了解。特别令人感兴趣的是二氧化碳和二氧化硫等气体的交换。研究人员将通过检查熔岩湖来解决这个问题，熔岩湖是开放喷口火山的岩浆管道的表面表现形式。开口式火山是地球内部和地表之间物质交换的主要场所。管道是复杂的系统，在这里进行脱气、冷却和结晶。这些过程导致浮力的强烈变化，从而导致对流，以及材料性质的变化，使流动行为变得复杂。熔岩湖很罕见，但它们存在于所有构造环境中，也存在于其他星球上。对熔岩湖的观测已经证实了岩浆管道中存在内部循环，该项目旨在更好地约束这种动态现象。更好地了解熔岩湖和开口管道的动力学，是限制地球内部、熔岩湖和大气之间质量交换率的时间和长度尺度的关键。研究小组将通过分析在三个活跃的熔岩湖--夏威夷的Halemaumau陨石坑、埃里伯斯山(南极洲)和Erta Ale(非洲)--积累的大量视觉和热数据，解决熔岩湖表面观测与开口式火山管道脱气和对流模型之间的联系。他们还将在可见光和热像片上使用视频测速仪，提取对流湖泊的详细表面速度场，并量化与时间相关的地壳板块配置。随后，他们将寻找地表运动与同时收集的其他数据集之间的相关性，包括微震活动和气体排放，以调查脱气和翻转的内部过程。这项工作的一个成果将是一组高质量的地质系统对流观测，数值模型可以根据这些观测结果进行基准测试。测得的速度场将作为湖泊数值正演模型的约束条件。他们计划开发一种数值建模框架，能够捕捉熔岩和岩浆管道所具有的复杂的多相系统。然后，研究人员将使用计算流体动力学软件包OpenFOAM，这是一个开源、模块化和灵活的软件包，并允许集成广泛的物理过程。具体地说，他们的目标是开发一个建模框架，该框架将建立在OpenFOAM现有组件的基础上：具有温度相关流变性的热对流、气液两相流以及凝固/熔化。在框架开发的每个阶段，研究人员将检查内部参数，如补给事件、管道配置和挥发含量对其在表面表达的影响(板块运动和气体排放)。

The main objective of this project is to advance our understanding of circulation in magmatic conduits and the interaction and mass exchange between the subsurface magmatic system, the surface and the atmosphere. Of particular interest is the exchange of gasses such as CO2 and SO2. The investigators will address this target by examining lava lakes, the surface expression of magmatic conduits at open-vent volcanoes. Open-vent volcanoes are a primary locale for the exchange of materials between the Earth's interior and the surface. Conduits are complex systems, where degassing, cooling and crystallization take place. These processes lead to strong variability in buoyancy, thus causing convection, and in material properties, making flow behavior complicated. Lava lakes are rare, yet they are represented at all tectonic environments, as well as on other planets. Observations at lava lakes have already confirmed the existence of internal circulation in magmatic conduits, and this project aims to put better constraints on this dynamic phenomenon. Better understanding of the dynamics of lava lakes and open-vent conduits is key to constraining time and length scales for mass exchange rates between the Earth's interior, lava lake and atmosphere. The research team will address the connection between surface observations at lava lakes and models of degassing and convection at open-vent volcanic conduits, by analyzing large collections of visual and thermal data accumulated at three active lava lakes -Hawaii's Halemaumau crater, Mount Erebus (Antarctica), and Erta Ale(Africa). They will also employ video velocimetry on visible and thermal footage, extract detailed surface velocity fields of the convecting lakes, and quantify the time-dependent crustal plate configuration. Subsequently, they will search for correlations between the surface motions and other data sets collected simultaneously, including microseismicity and gas emission, to investigate the internal processes of degassing and overturns. A product of this work will be a high-quality set of observations of convection in a geologic system, against which numerical models could be benchmarked and tested. The measured velocity fields will be used as constraints for numerical forward models of the lakes. They plan to develop a numerical modeling framework capable of capturing the complex multi-phase systems, which lava and magma conduits are. The investigators will then use the computational fluid dynamics package OpenFOAM, an open-source, modular and flexible package, and allows for the integration of a wide range of physical processes. Specifically, they aim to develop a modeling framework that will build upon existing components of OpenFOAM: thermal convection with temperature-dependent rheology, gas-liquid two-phase flow, and solidification/melting. At every stage of the framework development, the investigators will examine the influence of internal parameters such as recharge events, conduit configuration and volatile content on their expression at the surface (plate motion and gas emission).