CAREER: Triggering Eruptions: Determination of Pressure-Temperature-Composition-time Histories for Magma Bodies Preceding Eruption

项目描述：每年有50到70座火山喷发，危及当地居民，扰乱空中交通，破坏财产和基础设施。监测火山气体排放的成分、当地地表变形以及与火山有关的地震的大小和位置，可以提供有关活火山下岩浆储存和运动的丰富信息。然而，我们仍然缺乏足够的背景来解释这些数据，这样我们就可以明确地预测岩浆的运动何时会在未来几周到几年内导致喷发。为了建立必要的背景，该项目将重建导致美国不同构造环境中三个不同爆发火山过去喷发的岩浆体的详细历史，包括一个能够发生小型和超大型火山喷发的火山口火山（黄石，WY），一个安山岩弧火山（沙斯塔山，CA）和一个更复杂的弧后火山（梅迪辛湖，CA）。特别是，该项目将使用岩浆系统研究中最令人兴奋的新工具之一——扩散计时法——一种利用化学分带矿物中元素或同位素的扩散来确定地质过程的时间尺度的工具——和相平衡来确定这些岩浆体的压力-温度-成分-时间历史，并确定它们特定的喷发触发器。这些历史可以用来开发喷发触发的概念模型，用于喷发预测和火山危害评估。该项目使用尖端研究来重建导致过去火山爆发的过程，培训未来的地球科学交流科学家，并每年与8000多名K-12学生分享这些成果。21世纪的成功公民将越来越需要对STEM思想、实践和领域感兴趣和熟悉，公众自我报告的科学理解几乎有一半是通过课堂外的学习经验获得的。同时，对STEM的兴趣在青春期下降。为了应对这些机遇和挑战，亚利桑那州立大学（ASU）的研究生将参加科学传播课程，其中包括在非正式环境中广泛传播科学研究的培训，以及“科学幕后”视频的开发。这些视频将作为教育活动和后续评估的基础，每年约有8000名K-12学生参观亚利桑那州立大学地球与太空探索学院。技术说明：火山科学中最突出的问题之一是火山爆发是如何以及何时触发的。岩石学工具和火山沉积物的原位地球化学技术的进步，使测定喷发前岩浆体的压力、温度和成分的准确度达到了前所未有的水平。同时，扩散计时技术的进步使我们能够在火山爆发前数周至数千年计算间歇岩浆事件的时间。该项目将整合这两套工具，并利用岩浆内部的主要和微量元素分区，包括喷涌喷发和爆炸喷发，以及在超级喷发期间，以确定其喷发前的压力-温度-组成-时间（P-T-X-t）历史。开展本研究的具体方法包括通过SIMS和NanoSIMS进行高分辨率的原位地球化学分析，扩散计时法，以及通过实验和流岩- melt模型确定的岩石相平衡，以确定个别火山喷发的具体触发因素和相关的时间尺度。将比较位于板块内、俯冲带和弧后构造环境的火山的喷发前历史。此外，在含钾长石中测定Mg扩散率的一组关键的1atm实验将允许对更大范围的自然样品进行解释。这些自然样品的研究结果将为解释火山监测数据提供一个概念模型。

Project Description:Fifty to seventy volcanoes erupt each year and endanger the local population, as well as disrupt air traffic and damage property and infrastructure. Monitoring the composition of volcanic gas emissions, local ground surface deformation and the size and location of volcanism-related earthquakes provides a wealth of information about magma storage and movement beneath active volcanoes. However, we still lack a sufficient context to interpret this data such that we can categorically predict when the movement of magma will lead to an eruption in the coming weeks to years. In order to build the necessary context, this project will reconstruct the detailed histories of magma bodies in the days to years leading to past eruptions at three different explosive volcanoes located in varied tectonic settings in the U.S., including a caldera volcano capable of both small and very large volcanic eruptions (Yellowstone, WY), an andesitic arc volcano (Mt. Shasta, CA) and a more mafic rear-arc volcano (Medicine Lake, CA). In particular, this project will use one of the most exciting new tools in the study of magmatic systems, diffusion chronometry - a tool which exploits the diffusion of elements or isotopes in chemically zoned minerals to determine the timescales of geologic processes - and phase equilibria to determine pressure-temperature-composition-time histories for these magma bodies and identify their specific eruption triggers. These histories can then be used to develop conceptual models of eruption triggers for eruption forecasting and volcano hazard assessments. This project uses cutting edge research to reconstruct the processes leading to past volcanic eruptions, training for future scientists in geoscience communication, and sharing these outcomes with more than 8000 K-12 students annually. Successful citizenship in the 21st century will increasingly require an interest in and comfort with STEM ideas, practices and fields and almost half of the public's self-reported science understanding is gained through learning experiences outside of the classroom. Simultaneously interest in STEM is shown to decline during adolescence. In order to address these opportunities and challenges, graduate students at Arizona State University (ASU) will participate in a Science Communication class, which includes training in communicating scientific research broadly in informal settings and the development of "behind the scenes of science" videos. These videos will be used as the foundation of educational activities and follow-up assessments for the approximately 8000 K-12 visitors to the School of Earth & Space Exploration at ASU each year.Technical Description:One of the most outstanding questions in volcano science is how and when volcanic eruptions are triggered. Advances in petrologic tools and in-situ geochemistry of volcanic deposits now enable unprecedented fidelity in determinations of the pressures, temperatures, and compositions of magma bodies preceding eruption. Simultaneously advances in diffusion chronometry permit calculations of the timing of punctuated magmatic events in the weeks to millennia before eruption. This project will integrate these two sets of tools and exploit intra-crystalline major and trace element zoning in magmas erupted both effusively and explosively, as well as during supereruptions, to determine their pre-eruption pressure-temperature-composition-time (P-T-X-t) histories. Specific methods to conduct this research include high resolution in-situ geochemistry via SIMS and NanoSIMS, diffusion chronometry, and petrologic phase equilibria determined from experiments and rhyolite-MELTS modeling to identify the specific eruption triggers and the associated timescales for individual volcanic eruptions. Pre-eruptive histories will be compared for eruptions at volcanoes located in intra-plate, subduction zone, and back arc tectonic settings. In addition, a critical set of 1 atm experiments to determine Mg diffusivity in K-bearing feldspar will allow interpretation of a greater range of natural samples. The results from these studies of natural samples will provide a conceptual model for interpreting volcanic monitoring data.