Active Lava Lakes as a Window into Magma and Volcano Dynamics

该项目的主要目标是提高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认识。特别令人感兴趣的是气体如CO2和SO2的交换。研究人员将通过检查熔岩湖来解决这一目标，熔岩湖是开放式火山岩浆管道的表面表现。开放式火山是地球内部和表面之间物质交换的主要场所。管道是一个复杂的系统，在那里进行脱气、冷却和结晶。这些过程导致浮力的强烈变化，从而引起对流，并在材料特性，使流动行为复杂。熔岩湖是罕见的，但它们在所有构造环境中都有代表，以及在其他行星上。对熔岩湖的观测已经证实了岩浆管道中存在内部循环，本项目旨在更好地限制这种动态现象。更好地了解熔岩湖和开放式通风管道的动态是限制地球内部，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火山口、埃里伯斯山（南极洲）和Erta Ale（非洲）--积累的大量视觉和热数据，来解决熔岩湖表面观测与开放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镜头上采用视频测速技术，提取对流湖的详细表面速度场，并量化随时间变化的地壳板块结构。随后，他们将寻找地表运动与同时收集的其他数据集（包括微震活动和气体排放）之间的相关性，以研究脱气和翻转的内部过程。这项工作的一个成果将是一套高质量的地质系统对流观测数据，可以据此对数值模型进行基准测试和测试。所测得的速度场将被用作湖泊数值正演模型的约束条件。他们计划开发一个能够捕获复杂的多相系统的数值建模框架，熔岩和岩浆管道就是这样。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，并允许集成各种物理过程。具体来说，他们的目标是开发一个建模框架，该框架将建立在OpenFOAM的现有组件上：具有温度依赖性流变学的热对流，气液两相流和固化/熔化。在框架开发的每个阶段，调查人员将检查内部参数的影响，如补给事件，导管配置和挥发性含量对其在表面的表达（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).