EAR-PF: Does eruption trigger mechanism ultimately control eruption style at arc volcanoes?

Rebecca deGraffenried博士被授予EAR博士后奖学金，在亚利桑那州立大学开展研究和教育计划。deGraffenried博士的项目旨在了解决定火山喷发爆炸性的潜在因素，以便在火山显示活动迹象时准确预测火山危害。最近的研究表明，岩浆开始向地表流动的具体原因（“喷发触发器”）会影响最终喷发的爆炸性，尽管目前还不清楚为什么会这样。喷发触发和岩浆上升到地表的速率（岩浆上升速率）都被认为与给定岩浆体的内部压力有关。因此，本项目旨在测试不同的喷发触发是否会产生不同的岩浆上升速率，并将从美国两座高威胁火山St. Helens和Mt. Hood的一系列喷发方式中确定上升速率和触发机制。这项研究不仅揭示了控制喷发方式的潜在过程，而且还将推进对威胁太平洋西北部社区的两座非常活跃的火山的行为和危害的认识。这项工作对火山风险和危害评估有影响，并将培养本科生的研究方法。此外，deGraffenried博士将与亚利桑那州立大学的“询问地球和空间科学家”合作，就该项目的结果与更广泛的社区进行交流。本项目是对喀斯喀特火山弧的两座火山进行岩石学调查。由于岩浆成分和喷发方式的不同，俯冲带火山对生物群落尤其危险。因此，了解影响火山喷发方式的因素对这些火山尤为重要。尽管圣海伦火山和胡德火山的喷发历史截然不同，但它们都有可能在爆发时威胁到社区。本研究将利用正辉石中Fe-Mg浓度梯度的扩散模型来确定从储存到地表上升的时间尺度。此外，每次喷发的触发机制将由晶体/熔体平衡、温度计和湿度计确定。总的来说，这些数据将提供一系列喷发风格和岩浆组成的见解，代表了两个感兴趣的火山，并阐明了以前未被探索的喷发开始和喷发结果之间的联系。这些研究的结果在灾害预报中是有用的，因为地球物理监测数据可以用来识别某些喷发的触发因素。作为这项研究更广泛影响的一部分，deGraffenried博士将在亚利桑那州立大学地球与空间探索学院网站上的“向地球和空间科学家提问”系列中发表关于火山过程的文章。这个系列是针对K-12学生的，回答了这些学生关于地球是如何运作的问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Rebecca deGraffenried has been granted an EAR Postdoctoral Fellowship to carry out research and education plans at the Arizona State University. Dr. deGraffenried’s project is designed to to understand the underlying factors that dictate how explosive a volcanic eruption will be in order to accurately forecast volcanic hazards when a volcano shows signs of activity. Recent work shows that the specific reason a magma begins traveling to the surface (the “eruption trigger”) influences how explosive the eventual eruption will be, although it is unclear why this is true. Both the eruption trigger and rate at which magma rises to the surface (magma ascent rate) are thought to be related to the amount of internal pressure in a given magma body. Therefore, this project aims to test whether different eruption triggers produce different magma ascent rate and will determine the ascent rates and trigger mechanisms from a range of eruption styles at Mt. St. Helens and Mt. Hood, two high threat volcanoes in the United States. Not only will this study shed light on an underlying process that controls eruption style, but it will also advance knowledge about the behavior and hazards of two very active volcanoes that threaten communities in the Pacific Northwest. The work has implications for volcanic risk and hazard assessment and will train an undergraduate in research methods. Additionally, Dr. deGraffenried will partner with Arizona State University’s “Ask an Earth and Space Scientist” to communicate with the broader community about the results of this project. This project is a petrologic investigation of two volcanoes in the Cascades volcanic arc. Subduction zone volcanoes in particular are hazardous to communities due to the range of magma compositions and eruption styles possible. Therefore, understanding the factors that influence volcanic eruption style is particularly critical for these volcanoes. Mt. St. Helens and Mt. Hood are both poised to threaten communities in the event of eruption, though they have vastly different eruptive histories. This study will utilize diffusion modeling of Fe-Mg concentration gradients in orthopyroxene to determine the timescale of ascent from storage to the surface. Additionally, eruption trigger mechanism for each eruption of interest will be determined by crystal/melt equilibrium, thermobarometers, and hygrometers. Altogether, these data will provide insights into a range of eruption styles and magma compositions represented by the two volcanoes of interest and elucidate a previously unexplored connection between eruption initiation and eruption outcome. The results of these studies could be useful in hazard forecasts as geophysical monitoring data can be used to identify certain eruption triggers. As a part of the broader impacts of this study, Dr. deGraffenried will contribute articles on volcanic processes to the “Ask an Earth and Space Scientist” series on the Arizona State University School of Earth and Space Exploration website. This series is geared towards K-12 students and answers questions these students have about how the Earth works.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.