Collaborative Research: Testing the controls on eruption size and style at intermediate arc volcanoes: Evidence from the Holocene record at Augustine Volcano, USA

该项目由岩石学和地球化学以及刺激竞争性研究（EPSCoR）计划的既定计划共同资助。阿拉斯加的奥古斯丁火山是美国最活跃的火山之一，被美国地质调查局认为是一个非常高的威胁。火山造成的危害取决于喷发的规模和类型，许多问题仍然是什么控制着奥古斯丁等中间弧火山的喷发特征。例如，大规模的爆炸性喷发是由地壳浅层的大量岩浆供应驱动的，还是由更快的上升速率驱动的，还是两者兼而有之？从奥古斯丁火山喷发的史前火山灰（名为火山灰B和火山灰M）可以提供关于喷发行为如何随时间变化的见解。该项目的目标是调查岩浆管道系统和喷发爆炸性之间的联系。它将针对决定喷发方式的两个主要因素：岩浆成分和岩浆通过地壳上升的速度。这项工作将产生重要的社会效益，特别是与美国的火山灾害有关，并广泛适用于全球其他中间弧火山。最后，该项目启动了阿拉斯加火山观测站、高露洁大学和米德尔伯里学院之间新的火山观测-学术合作伙伴关系。这种伙伴关系将加速基础科学向应用和监测的转化，这将在两所本科院校提供积极的研究型课程。该项目的目标是：1）使用全岩（浮石）、斑晶、玻璃和熔融包裹体地球化学数据来确定地下岩浆储层的数量、几何形状和关系，这些地下岩浆储层为在奥古斯丁产生Tephra M和Tephra B单元的喷发提供了补给，2）调查岩浆上升速率的指标，如挥发物浓度、晶体结构，以及喷发物质中的气泡结构，3）通过将火山岩B和M与历史上和更古老的史前和更新世沉积物进行比较，表征火山管道系统如何随时间演变，以及4）通过在火山岩M和B的地层中进行详细取样，研究喷发风格的小规模变化，有针对性的努力，以表征微晶片穷人和微晶片丰富的样品。这将解决奥古斯丁记录中存在的一些观测偏差，并将有助于描述这种偏差在中间弧火山中的潜在规模和重要性。该项目的数据将为推动上升和爆炸性的物理和化学过程提供新的限制，并确定岩浆储存库如何随时间演变。该奖项反映了NSF的法定使命，并被认为值得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来支持。

This project is jointly funded by the Petrology and Geochemistry and the Established Program to Stimulate Competitive Research (EPSCoR) programs. Augustine Volcano in Alaska is one of the most frequently active volcanoes in the US and is considered a very high threat by the U.S. Geological Survey. The hazards posed by a volcano depend on the size and style of an eruption, and many questions remain as to what controls these eruption characteristics at intermediate arc volcanoes like Augustine. For example, are large and explosive eruptions driven by larger volumes of magma supply at shallow depths in the crust, or by faster ascent rates, or both? Prehistoric tephras (named Tephra B and Tephra M) that erupted from Augustine Volcano can provide insight into how eruptive behavior changes through time. This project has as a goal to investigate the links between magma plumbing systems and eruption explosivity. It will target two of the primary factors that determine eruption style: magma composition and the rate at which the magma ascends through the crust. Important societal benefits will emerge from this work, specifically related to volcanic hazards in the US, and that are broadly applicable to other intermediate arc volcanoes globally. Finally, this project initiates new volcano observatory-academic partnerships between the Alaska Volcano Observatory, Colgate University, and Middlebury College. This partnership will accelerate the translation of basic science to applications and monitoring that will provide active research-based curricula at two undergraduate institutions. The goals of this project are to: 1) use whole rock (pumice), phenocryst, glass, and melt inclusion geochemical data to identify the number, geometry, and relationships between the subsurface magmatic reservoirs that fed the eruptions that produced units Tephra M and Tephra B at Augustine, 2) investigate indicators of magmatic ascent rate such as volatile concentrations, crystal textures, and bubble textures within the erupted material, 3) characterize how volcanic plumbing systems evolve through time by comparing tephras B and M to historic and older prehistoric and Pleistocene deposits, and 4) investigate small-scale variability in eruption style through detailed sampling within the stratigraphy of Tephras M and B, with a targeted effort to characterize both microlite-poor and microlite-rich samples. This will resolve some of the observational bias that exists in Augustine’s record, and will help characterize the potential magnitude and importance of this bias at intermediate arc volcanoes. Data from this project will provide new constraints on the physical and chemical processes that drive ascent and explosivity and determine how magma storage reservoirs evolve over time.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.