Investigating the volatile evolution and decompression rate of high-intensity basaltic eruptions

关于产生高爆炸性火山喷发的驱动因素的知识主要集中在长英质(高硅质演化熔体)喷发上。然而，尽管镁铁质火山活动是地球上最常见的火山活动类型，而且它们还可能引发毁灭性的社会和环境影响，但类似爆炸性强度的镁铁质(演化程度较低的高镁熔体)喷发仍有待研究。该项目旨在通过重建熔融包裹体的化学演化和挥发收支来提高对镁铁质火山作用的理解。熔融包裹体是晶体生长过程中捕获的小熔滴，保存了地质记录中最具爆炸性的镁铁质火山喷发的历史。这项研究将提供有关镁铁质岩浆上升到爆炸喷发的时间尺度的见解，这可以用来为喷发响应努力和预测提供信息。研究小组将与美国地质调查局的夏威夷火山观测站(HVO-USGS)合作，在全球火山监测和风险评估机构之间传播知识。这项工作还将通过支持活火山研究中心(CSAV)夏季课程的一个单元，扩大地球化学法在火山监测和应对方面的全球应用。该项目将支持研究生和本科生在康奈尔大学和HVO大学进行不同的微观分析技术培训，以及他们在理解喷发方面的应用。该项目的成果将被纳入康奈尔大学的地球材料和火山学课程。最后，该项目将通过在康奈尔大学、HVO-USGS、曼彻斯特大学、LDEO-哥伦比亚大学、加州奥克兰大学和锡拉丘兹大学之间建立合作来加强研究和教育的基础设施。高强度爆炸性喷发(次普林尼安、普林尼安和超普林尼安，火山爆炸性指数为6)导致全球环境影响，并具有极大的破坏性社会影响。在这些喷发中，镁铁质喷发是研究最少的，是迫切需要进一步研究的关键终端成员。特别令人感兴趣的是确定它们的岩浆减压速率(dp/dt)，因为这一参数在确定玄武岩岩浆喷发动力学中的火山作用类型方面起着至关重要的作用。该项目将研究玄武岩普林尼期到次普林尼期喷发的挥发分演化和减压。这些喷发代表了玄武岩火山活动中最灾难性和最不被理解的一些终端成员。重建它们的喷发历史将解决以下问题：1)玄武岩普林尼期喷发的喷发前条件和脱气记录是什么？为了准确地约束岩浆条件、喷发前和喷发期间挥发性饱和和脱气的演化，以及减压路径，该团队将使用橄榄石托管的MIS。2)玄武岩普林尼期喷发的减压速率是多少？对拟议的喷发案例研究的岩浆减压速率的估计需要通过使用数值模型、实验和晶体结构来间接改进或约束。这项工作旨在用两种基于依赖时间的化学反应的岩石学工具来补充挥发分的演化史：挥发分在橄榄石赋存海湾的扩散和H在橄榄石晶体中的浓度梯度。3)高强度镁铁质喷发是否表现出减压速率与喷发强度之间的相关性？目前的数据表明，低爆炸性和中等爆炸性的玄武岩喷发显示出减压速度和喷发强度之间明显的正相关。然而，这些数据无法用于更高级别的喷发。这个项目将通过新的减压率研究和文献数据来回答这个问题。这个奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Knowledge of the driving factors in generating highly explosive volcanic eruptions has been mostly focused on felsic (evolved melts high in silica) eruptions. Nevertheless, mafic (less evolved melts high in magnesium) eruptions of similar explosivity intensity have yet to be studied, even though mafic volcanism is the most common type of volcanic activity on Earth, and they could also trigger devastating societal and environmental impacts. This project aims to improve understanding of mafic volcanism by reconstructing the chemical evolution and volatile budgets from melt inclusions, small droplets of melt trapped during crystal growth that preserved the history of the most explosive mafic eruptions in the geologic record. This study will provide insights on the timescales over which mafic magmas ascend to erupt explosively, which can be used to inform eruption response efforts and forecasts. The research team will collaborate with the U.S. Geological Survey’s Hawaiian Volcanic Observatory (HVO-USGS) to disseminate knowledge among global volcanic monitoring and risk assessment agencies. The work will also broaden the global use of geochemical techniques in volcano monitoring and response by supporting a module in the Center for the Study of Active Volcanoes (CSAV) summer course. This project will support graduate and undergraduate students through training in different micro-analytical techniques at Cornell and HVO, and their applications to understand eruptions. Results from this project will be incorporated into Earth Materials and Volcanology courses at Cornell. Finally, this project will enhance the infrastructure for research and education by establishing collaborations between Cornell University, HVO-USGS, the University of Manchester, LDEO-Columbia University, the University of Auckland, Caltech, and Syracuse University.High-intensity explosive eruptions (sub-Plinian, Plinian, and ultra-Plinian, with a volcanic explosivity index of 6+) result in global environmental effects and have great potential for devastating societal impacts. Among these eruptions, mafic eruptions are the least studied and represent a critical end-member urgently needing further investigation. Of particular interest is the determination of their magma decompression rates (dP/dt), as this parameter plays a crucial role in setting the style of volcanism in the eruption dynamics for basaltic magmas. This project will study the volatile evolution and decompression of basaltic Plinian to sub-Plinian eruptions. These eruptions represent some of basaltic volcanism's most catastrophic and least understood end-members. Reconstructing their eruption histories will address the following questions: 1) What is the record of pre-eruptive conditions and degassing that characterizes basaltic Plinian eruptions? To accurately constrain magmatic conditions, the evolution of volatile saturation and degassing before and during the eruption, and decompression pathways, the team will use olivine-hosted MIs. 2) What are the decompression rates of basaltic Plinian eruptions? Estimates of magma decompression rates for the proposed eruption case studies need to be improved or constrained indirectly using numerical models, experiments, and crystal textures. This work aims to complement the volatile evolution history with two petrological tools based on time-dependent chemical reactions: volatile diffusion across olivine-hosted embayments and concentration gradients of H+ in olivine crystals. 3) Do high-intensity mafic eruptions display a correlation between decompression rate and eruption magnitude? Current data suggest low and mildly explosive basaltic eruptions show a clear positive correlation between decompression rate and eruption magnitude. However, these data are not available for higher-magnitude eruptions. This project will answer this question with new decompression rates studies supplemented with literature data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.