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，危及当地人口，扰乱空中交通，破坏财产和基础设施。通过监测火山气体排放物的成分、当地地表变形以及与火山活动有关的地震的规模和位置，可以提供关于活火山下岩浆储存和运动的大量信息。然而，我们仍然缺乏足够的背景来解释这些数据，以便我们可以明确预测岩浆运动何时会导致未来几周到几年的喷发。为了建立必要的背景，该项目将重建岩浆体在几天到几年内的详细历史，导致过去位于美国不同构造环境中的三个不同爆炸性火山爆发，包括一个能够进行小型和大型火山喷发的破火山口（怀俄明州黄石），一个安山质弧火山（Mt.沙斯塔，加利福尼亚州）和一个更基性岩后弧火山（医药湖，加利福尼亚州）。 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，扩散测时法-一种利用化学分区矿物中元素或同位素的扩散来确定地质过程时间尺度的工具-和相平衡来确定这些岩浆体的压力-温度-成分-时间历史，并确定其特定的喷发触发因素。这些历史，然后可以用来开发概念模型的喷发触发喷发预测和火山灾害评估。该项目利用尖端研究来重建导致过去火山爆发的过程，为未来的科学家提供地球科学交流培训，并每年与8000多名K-12学生分享这些成果。世纪的成功公民将越来越需要对STEM思想，实践和领域的兴趣和舒适感，几乎一半的公众自我报告的科学理解是通过课堂外的学习经验获得的。 同时，对STEM的兴趣在青春期有所下降。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和“科学幕后”视频的开发。 这些视频将被用作教育活动的基础，并为亚利桑那州立大学地球空间探索学院每年约8000名K-12访问者提供后续评估。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引发的。岩石学工具和火山沉积物的原位地球化学的进步，现在使前所未有的精确度确定的压力，温度和岩浆体喷发前的成分。与此同时，扩散测时技术的进步允许计算爆发前数周到数千年的间断岩浆事件的时间。该项目将整合这两套工具，并利用溢出和爆炸以及超喷发期间岩浆中的晶体内主要和微量元素分区，以确定其喷发前的压力-温度-成分-时间（P-T-X-t）历史。进行这项研究的具体方法包括通过西姆斯和NanoSIMS进行的高分辨率原位地球化学，扩散测时法，以及从实验和流纹岩-熔融物建模中确定的岩石相平衡，以确定具体的喷发触发因素和个别火山喷发的相关时间尺度。将比较位于板内、俯冲带和弧后构造环境中的火山喷发的喷发前历史。此外，一组关键的1个大气压的实验，以确定镁的含钾长石扩散率将允许解释更大范围的天然样品。这些自然样本研究的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.