Collaborative Research: Degassing-Based Constraints on the Dynamics of Submarine Eruptions

动力学(上升速率、质量喷发速率、熔岩流速等)海底喷发约占地球年度火山活动的70%，基本上是未知的。这项研究将开发一种基于脱气的“地球测速仪”(即一种确定岩浆从岩浆室到海底最后安息地点的速度有多快的方法)。对于大洋中脊玄武岩，这将能够量化地球上最大的火山系统(即大洋中脊扩张中心)的喷发动力学，并有助于评估这些动力学如何影响巨大的大洋中脊系统的碳通量。将结合对海底火山熔岩流熔岩样本中的结构和挥发物的详细微观分析，以及一套独特的实验室实验，来量化大洋中脊玄武岩中的脱气和气泡形成的机制和速率。将在这些结果的基础上开发“地球测速仪”。这台地球测速仪将使我们能够了解和测量大洋中脊熔岩的流速、供给它们的喷发的减压速率，以及流动形态(席状流与枕状熔岩)如何反映喷发速率。分析将集中在2011年美国和加拿大西北海岸胡安德富卡山脊上的Axial火山喷发的样本上，这些样本绘制得很好，样本也很全面。这次喷发的样本将通过沿轴心火山喷发裂缝和流动路径收集的样本的挥发性浓度和气泡大小分布来分析脱气。一个中心挑战将是将温度、降压率和成分与挥发性浓度和泡囊种群联系起来。因此，将进行一系列使用天然的、二氧化碳过饱和的大洋中脊玄武岩的实验室减压和冷却实验，为模型计算提供见解和输入参数，从而使结果量化。2011年的Axial火山喷发将作为测试案例，用于改进脱气模型，并提供将研究成果纳入广泛适用的海底火山系统模型的工具。这项研究还将通过更严格和定量地评估海底玄武岩对二氧化碳脱气的控制，帮助改进对碳通量的估计。这项研究的更广泛影响包括对研究生和本科生的支持，以及通过已经计划的教师培训讲习班让调查人员与K-12 STEM教师接触。研究还将被纳入研究人员教授的课程，数据将通过NSF资助的数据管理设施免费向公众提供。

The dynamics (ascent rate, mass eruption rate, lava flow rate, etc.) of submarine eruptions, which account for roughly 70% of the Earth's annual volcanic activity, are essentially unknown. This research will develop a degassing-based "geospeedometer" (i.e., a method for determining how fast magma moves from its magma chamber to its final resting place on the sea floor). for mid-ocean ridge basalts that will allow quantification of eruption dynamics in Earth's largest volcanic system (i.e., the mid-ocean ridge spreading centers) and help to evaluate how those dynamics impact carbon fluxes from the vast mid-ocean ridge system. A combination of detailed microanalysis of textures and volatiles in lava samples from submarine volcanic lava flows and a unique set of laboratory experiments will be used to quantify the mechanisms and rates of degassing and vesiculation in mid-ocean ridge basalts. A "geospeedometer" will be developed on the basis of those results. This geospeedometer will allow us to understand and measure flow rates of mid-ocean ridge lavas, decompression rates of the eruptions feeding them, and how flow morphologies (sheet flow vs. pillow lava) reflect eruption rate. Analyses will be focused on samples from the well mapped and comprehensively sampled 2011 eruption of Axial Volcano on the Juan de Fuca Ridge off the northwest coast of the US and Canada. Samples from this eruption will be analyzed for degassing via volatile concentrations and vesicle-size distributions of samples collected along the Axial Volcano eruptive fissures and flow paths. A central challenge will be the linking of temerature, depressurization rate, and composition to volatile concentrations and vesicle populations. Thus, a series of laboratory decompression and cooling experiments using natural, CO2-supersaturated, mid-ocean ridge basalts will be undertaken to provide insights and input parameters for model calculations, leading to the quantification of results. the 2011 eruption of Axial Volcano will serve as the test case and be used to refine models of degassing and provide the vehicle for incorporating research reesults into broadly applicable models for submarine volcanic systems. The research will also help improve estimates of carbon flux by evaluating more rigorously and quantitatively the controls on seafloor basalt degassing of CO2. Broader impacts of the research include support of graduate and undergraduate students and engagement of the investigators with K-12 STEM teachers via already plannedteacher training workshops. Research will also be incorporated into courses taught by the investigators and data will be made freely available to the public through NSF-funded data management facilities.