Causes and Consequences of Holocene Mafic Explosive Volcanism in Central OR?

智力优势：该项目扩展了PI在小型“单成因”喷发方面的初步工作，这些喷发能够进行爆炸活动（具有火山灾害的后果），喷发方式和岩浆演化在很大程度上取决于气体和岩浆通过地壳的运输条件。这项工作提出了一些问题，气体迁移的机制，通过地壳的岩浆输送系统的时间演化，并控制结晶镁铁质岩浆的碎裂。建议通过关注两次全新世喷发的产物来研究小型镁铁质系统中活跃的物理和化学过程之间的联系：[1]桑德山，OR（年龄= c。3500年BP;体积=~0.9 km3）。这个喷口产生了一个大火山灰片（0.3立方千米），存款的均匀细（1 - 3毫米）粒度提出了有趣的问题，岩浆破碎。[2]Cinder Cone，CA.公元1666年的喷发是最年轻的火山渣锥在瀑布，并作为一个例子，同喷发成分的演变;此外，火山灰生产的情节可以与特定的熔岩流，从而允许评价之间的联系的物理和化学演变的喷发。这两个例子代表了危害评估的两个端元"类型"喷发（见下文）。为了补充拟议的实地研究，将进行模拟实验，以确定控制气体通过富含晶体的岩浆迁移的三相流动制度，并调查晶体对岩浆膨胀和破碎的影响。最后，将进行实验，以检查控制临时岩浆存储在岩槛复合体在地壳上部，这些实验的结果将不仅适用于岩石学研究，但也火山monitoring.Broader影响：这项工作的一个重要的更广泛的影响将是发展的全面火山灾害评估中央OR。这种"以社区为中心"的危险评估将不同于传统的"以火山为中心"的评估，不仅通过将多个火山源，而且在使用数据从两个"类型"的喷发，以开发现实的火山灰扩散模型的范围内的风条件预计为弯曲OR地区。存款数据将在谷歌地球（kml）格式编制的学生在领导PI的地质灾害类。该项目还将部分资助三名研究生完成他们在原始资助下开始的博士论文：Dan Ruscitto正在分析熔体包裹体成分，作为对俄勒冈州中部俯冲带熔体起源的更大研究的一部分。（与P. Wallace）;丹尼尔·麦凯正在研究物理火山学、岩石学和来自纽贝里火山和中央OR瀑布的镁铁质喷发的危险（与K。Cashman）;伊索尔德·贝林已经进行了所有的模拟实验，并将研究气体迁移、膨胀和富含晶体的岩浆破碎之间的联系。Cashman和A. Rempel）。此外，McKay和Cashman正在帮助自然和文化历史博物馆（UO）开发一个新的展览，该展览将纳入这项工作的成果。最后，这项工作涉及与美国地质勘探局（迈克尔·克莱恩;煤渣锥），瑞士日内瓦大学（科斯坦扎·博纳多纳;火山灰建模）和英国布里斯托大学（艾莉森·鲁斯特·杰里米菲利普斯;模拟实验）的同事合作。&

Intellectual Merit: This project extends initial work by the PIs on small 'monogenetic' eruptions that are capable of explosive activity (with consequences for volcanic hazards), and for which eruption style and magma evolution depend in large part on the conditions of both gas and magma transport through the crust. This work has raised questions regarding mechanisms of gas migration, temporal evolution of magma delivery systems through the crust, and controls on fragmentation of crystalline mafic magma. It is proposed to examine links between physical and chemical processes active in small mafic systems by focusing on products of two Holocene eruptions: [1] Sand Mountain, OR (age = c. 3500 yr bp; volume = ~ 0.9 km3). This vent produced a large tephra sheet (0.3 km3), and the uniformly fine (1-3 mm) grain size of the deposit raises interesting questions about magma fragmentation.[2] Cinder Cone, CA. This 1666 AD eruption is the youngest scoria cone in the Cascades, and serves as an example of syn-eruptive compositional evolution; moreover, episodes of tephra production can be related to specific lava flows, thus allowing evaluation of links between the physical and chemical evolution of the eruption. These two examples represent two end-member 'type' eruptions for hazard assessment (below). To complement the proposed field studies, analog experiments will be conducted to define three-phase flow regimes that control gas migration through crystal-rich magmas and to investigate the effect of crystals on magma expansion and fragmentation. Finally, experiments will be conducted to examine controls on temporary magma storage in sill complexes within the upper crust; the results of these experiments will have applicability not only to petrologic studies but also to volcano monitoring.Broader Impacts: An important broader impact of this work will be development of a comprehensive volcanic hazard assessment for central OR. This 'community-centric' hazard assessment will differ from traditional 'volcano-centric' assessments not only by incorporating multiple volcanic sources, but also in using data from the two 'type' eruptions to develop realistic tephra dispersion models for the range of wind conditions expected for the Bend OR region. Deposit data will be compiled in Google Earth (kml) format by students in the led PI's Geologic Hazards class. This project will also partially fund three graduate students to complete PhD dissertations that they started under the original grant: Dan Ruscitto is analyzing melt inclusion compositions as part of a larger study of the origin of subduction zone melts in central OR (with P. Wallace); Daniele McKay is studying the physical volcanology, petrology, and hazards of mafic eruptions from both Newberry Volcano and the central OR Cascades (with K. Cashman); Isolde Belien has conducted all analog experiments and will investigate links between gas migration, expansion, and fragmentation of crystal-rich magmas (with K. Cashman and A. Rempel). Additionally, both McKay and Cashman are helping to develop a new display at the Museum of Natural and Cultural History (UO) that will incorporate results from this work. Finally, this work involves collaborations with colleagues from the USGS (Michael Clynne; Cinder Cone), University of Geneva, Switzerland (Costanza Bonadonna; tephra modeling), and the University of Bristol, UK (Alison Rust & Jeremy Phillips; analog experiments).