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

项目简介：每年有50至70座火山喷发，危及当地居民，扰乱空中交通，损坏财产和基础设施。监测火山气体排放的组成、当地地表变形以及与火山作用有关的地震的大小和位置，提供了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，以至于我们可以明确预测岩浆运动将在未来几周到几年内导致火山喷发的时间。为了建立必要的背景，该项目将重建导致过去几天到几年美国不同构造环境中三座不同火山喷发的岩浆体的详细历史，包括一座能够同时发生小型和超大型火山喷发的火山口火山(黄石，怀俄明州)，一座安山弧形火山(Mt.加利福尼亚州沙斯塔)和一座更镁铁质的弧后火山(加利福尼亚州梅迪辛湖)。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--一种利用元素或同位素在化学分区矿物中的扩散来确定地质过程的时间尺度的工具--以及相平衡，以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。然后，这些历史可以用来开发喷发触发因素的概念模型，用于喷发预测和火山危险评估。该项目使用尖端研究来重建导致过去火山喷发的过程，培训未来的科学家进行地球科学交流，并每年与8000多名K-12学生分享这些成果。在21世纪，成功的公民身份将越来越需要对STEM的想法、实践和领域感兴趣和适应，而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历获得的。与此同时，在青春期，人们对STEM的兴趣有所下降。为了应对这些机遇和挑战，亚利桑那州立大学(亚利桑那州立大学)的研究生将参加科学传播学课程，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”视频的制作。这些视频将被用作教育活动和后续评估的基础，每年约有8000名K-12游客参观亚利桑那州立大学地球与航天探索学院。技术描述：火山科学中最突出的问题之一是火山喷发是如何以及何时触发的。岩石学工具和火山沉积的原位地球化学的进步，现在能够前所未有地准确地确定喷发前的岩浆体的压力、温度和成分。同时，扩散计时学的进步使我们能够计算出火山喷发前几周到几千年内不时发生的岩浆事件的时间。该项目将整合这两套工具，并利用喷出和爆炸喷发以及超喷发期间岩浆中的晶内主量和微量元素分带，以确定其喷发前压力-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SIMS和NanoSIMS进行的高分辨率原位地球化学、扩散计量学和通过实验确定的岩石学相平衡，以及为确定个别火山喷发的特定喷发触发因素和相关时间尺度而建立的流纹岩-熔体模型。将比较位于板内、俯冲带和弧后构造环境中的火山喷发前的历史。此外，一组关键的1大气压实验，以确定镁在含钾长石中的扩散系数，将允许解释更大范围的自然样品。这些对自然样本的研究结果将为解释火山监测数据提供一个概念性模型。

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.