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

Rebecca deGraffenried博士已被授予博士后奖学金，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险。 最近的研究表明，岩浆开始向地表移动的具体原因（“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这是真的。喷发的触发和岩浆上升到地表的速度（岩浆上升速度）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因素是否会产生不同的岩浆上升速率，并将从一系列喷发类型中确定上升速率和触发机制。圣海伦斯和山。胡德，美国的两座高威胁火山。这项研究不仅揭示了控制喷发方式的基本过程，而且还将促进对威胁太平洋西北部社区的两个非常活跃的火山的行为和危害的了解。这项工作对火山风险和灾害评估有影响，并将对一名大学生进行研究方法方面的培训。此外，deGraffenried博士将与亚利桑那州州立大学的“问地球和空间科学家”合作，与更广泛的社区交流该项目的结果。该项目是对喀斯喀特火山弧中的两座火山进行岩石学调查。俯冲带的火山由于岩浆成分和喷发方式的不同，对社区特别危险。因此，了解影响火山喷发风格的因素对这些火山尤为重要。山圣海伦斯和山。胡德都准备在爆发时威胁社区，尽管它们有着截然不同的爆发历史。本研究将利用铁镁浓度梯度的扩散模型，在斜方辉石，以确定从存储到表面的上升的时间尺度。此外，将通过晶体/熔体平衡、温压计和湿度计确定每次感兴趣喷发的喷发触发机制。总之，这些数据将提供一系列的喷发风格和岩浆成分所代表的两个火山的利益，并阐明了以前未探索的喷发开始和喷发结果之间的联系。这些研究的结果可用于灾害预测，因为地球物理监测数据可用于确定某些火山爆发的触发因素。作为这项研究更广泛影响的一部分，deGraffenried博士将为亚利桑那州立大学地球和空间探索学院网站上的“问地球和空间科学家”系列提供关于火山过程的文章。该系列面向K-12学生，并回答这些学生关于地球如何运作的问题。该奖项反映了NSF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.