CAREER: Characterizing the Physical/Chemical Evidence of Volcanic Lightning

职业：描述火山闪电的物理/化学证据

• 批准号: 1553878
• 负责人: Kimberly Genareau
• 金额: $ 43.39万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2023-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1553878&HistoricalAwards=false
• 关键词: CAREER; Characterizing; Physical; Chemical; Evidence

Volcanic eruptions and lightning strikes are two of the most impressive and destructive natural phenomena, but much is still unknown about the fundamental processes that allow these events to occur. An emerging new line of research is seeking to determine the complex relationship between explosive volcanism and lightning, specifically: The effect of lightning discharge on the textural and chemical properties of volcanic ash and the resulting signature of volcanic lightning occurrence in the geologic record. In addition to the formation of fulgurites as a result of cloud-to-ground lightning strikes, lightning-induced volcanic spherules (LIVS) form in the atmosphere from the physical transformation of volcanic ash particles into spheres of glass due to the high heat generated during lightning discharge. This project will characterize the physiochemical evidence of volcanic lightning by: 1) identifying LIVS in natural ash fall deposits and analyzing their textural/chemical properties using established methods; 2) performing a series of triggered lightning experiments on manufactured ash samples of known composition and grain size to characterize the physical/chemical effects of volcanic lightning on the samples using various analytical methods; 3) establishing a research team of graduate, undergraduate, and high school students to perform the experiments and analyze the samples; and 4) developing grade school curricula for teaching natural hazards in local schools in order to engage students in the Earth sciences. Fundamental questions addressed by this project, and the integral educational component that involves learners of all ages, may result in potentially transformative concepts the geosciences, atmospheric sciences, and hazard assessment. Textural and geochemical data acquired on the samples will provide evidence for volcanic lightning in the geologic record, allowing researchers to identify these events during eruptions that preceded or eluded human documentation. Results will also reveal the role that lightning plays in altering the chemical characteristics of the local environment. Additionally, the triggered lightning experiments, conducted on manufactured ash samples of known composition, will allow video documentation of fulgurite formation. Through scientific and community presentations, this project will build further interest in volcanology, atmospheric dynamics, and the complex interplay between these natural phenomena, not only in the scientific community, but also in schools and amongst the general public.The primary goal of this project is to characterize the physical/chemical evidence of volcanic lightning occurrence in tephra deposits, which will aid in understanding the frequency of volcanic lightning in the geologic record, contributing to advancing scientific knowledge of volcano-atmosphere interactions, which is an emerging new line of scientific research. Ash fall deposits from numerous volcanic eruptions in Alaska will be analyzed, as volcanic lightning was documented during these explosive events and samples were provided by the Alaska Volcano Observatory. Triggered lightning experiments will be conducted at the International Center for Lightning Research and Testing (ICLRT) on manufactured ash samples (pseudo-ash samples) of known composition and grain size. The established analytical methods that will be utilized for this project include: 1) Scanning electron microscope (SEM), transmission electron microscope (TEM), and electron spin resonance (ESR) examination of lightning-induced volcanic spherules (LIVS) present in natural ash samples to determine their textural and chemical characteristics; 2) ESR, Mossbauer, and titration analyses of both natural, unmodified ash and pre-experimental pseudo-ash; and 3) SEM, TEM, ESR, Mossbauer, and titration analyses of LIVS and fulgurites produced in the triggered lightning experiments. A research team of graduate, undergraduate, and high school students will perform the experiments and analyze the samples. The various analyses, when conducted on the pseudo-ash samples prior to and following the triggered lightning experiments, will allow a direct means to determine the effect of lightning discharge on the morphological transformation, general chemistry, and oxidation/Fe valence state of exposed materials. The natural ash samples will allow a chemical comparison between normal (i.e., unmodified) ash and any LIVS present in the deposits. Following publication of results, the videos of triggered lightning experiments will be displayed on the University of Alabama?s Tephra Lab website, on YouTube, and showcased in the Alabama Museum of Natural History, along with samples of both natural fulgurites and fulgurites created in the triggered lightning experiments. Fundamental questions addressed by this project, and the integral educational component that involves learners of all ages, may result in potentially transformative concepts the geosciences, atmospheric sciences, and hazard assessment. Textural and geochemical data acquired on the samples will provide evidence for volcanic lightning in the geologic record, allowing researchers to identify these events during eruptions that preceded or eluded human documentation. Results will also reveal the role that lightning plays in altering the chemical characteristics of the local environment. Additionally, the triggered lightning experiments, conducted on manufactured ash samples of known composition, will allow video documentation of fulgurite formation. Through scientific and community presentations, this project will build further interest in volcanology, atmospheric dynamics, and the complex interplay between these natural phenomena, not only in the scientific community, but also in schools and amongst the general public.

火山爆发和雷击是最令人印象深刻和最具破坏性的两种自然现象，但关于这些事件发生的基本过程，人们仍然知之甚少。一项新兴的研究正在试图确定爆炸性火山活动和闪电之间的复杂关系，特别是：闪电放电对火山灰的结构和化学性质的影响，以及地质记录中火山闪电发生的结果。除了由于云对地雷击而形成的闪电石外，由于闪电放电时产生的高热量，火山灰颗粒在大气中物理转化为玻璃球，从而形成雷击诱发的火山球粒（LIVS）。该项目将通过以下方式描述火山闪电的物理化学证据：1)识别天然灰烬落沉积物中的LIVS，并使用既定方法分析其结构/化学特性；2)对已知成分和粒度的人造火山灰样品进行一系列触发闪电实验，利用各种分析方法表征火山闪电对样品的物理/化学影响；3)组建由研究生、本科生和高中生组成的研究团队进行实验和样本分析；4)在当地学校开发自然灾害的小学课程，以使学生参与地球科学。本项目解决的基本问题，以及涉及所有年龄段学习者的整体教育组成部分，可能导致潜在的地球科学、大气科学和危害评估概念的变革。从样本中获得的结构和地球化学数据将为地质记录中的火山闪电提供证据，使研究人员能够在人类记录之前或之前确定火山爆发期间的这些事件。结果还将揭示闪电在改变当地环境化学特征方面所起的作用。此外，在已知成分的人造灰烬样本上进行的触发闪电实验，将允许对闪电形成的视频记录。通过科学和社区的介绍，该项目将进一步建立对火山学、大气动力学以及这些自然现象之间复杂相互作用的兴趣，不仅在科学界，而且在学校和公众中。该项目的主要目标是表征火山闪电在火山沉积物中发生的物理/化学证据，这将有助于了解地质记录中火山闪电的频率，有助于推进火山-大气相互作用的科学知识，这是一个新兴的科学研究方向。由于火山闪电在这些爆炸事件中被记录下来，阿拉斯加火山观测站提供了样本，因此将对阿拉斯加许多火山喷发产生的火山灰沉积物进行分析。触发闪电实验将在国际闪电研究和测试中心（ICLRT）对已知成分和粒度的人造灰烬样本（伪灰烬样本）进行。本项目将采用的既定分析方法包括：1)扫描电子显微镜（SEM）、透射电子显微镜（TEM）和电子自旋共振（ESR）检查天然火山灰样品中存在的闪电诱发火山球粒（LIVS），以确定其结构和化学特征；2)自然灰分、未改性灰分和实验前伪灰分的ESR、穆斯堡尔和滴定分析；3)对触发闪电实验中产生的LIVS和电流石进行SEM、TEM、ESR、穆斯堡尔和滴定分析。一个由研究生、本科生和高中生组成的研究小组将进行实验并分析样本。在触发闪电实验之前和之后对伪灰样品进行的各种分析，将允许直接方法确定闪电放电对暴露材料的形态转变、一般化学和氧化/铁价态的影响。天然灰分样品将允许在正常（即未改性）灰分和沉积物中存在的任何LIVS之间进行化学比较。在结果公布后，触发闪电实验的视频将在阿拉巴马大学展出。在阿拉巴马州自然历史博物馆展出，同时展出的还有自然闪电和触发闪电实验中产生的闪电的样本。本项目解决的基本问题，以及涉及所有年龄段学习者的整体教育组成部分，可能导致潜在的地球科学、大气科学和危害评估概念的变革。从样本中获得的结构和地球化学数据将为地质记录中的火山闪电提供证据，使研究人员能够在人类记录之前或之前确定火山爆发期间的这些事件。结果还将揭示闪电在改变当地环境化学特征方面所起的作用。此外，在已知成分的人造灰烬样本上进行的触发闪电实验，将允许对闪电形成的视频记录。通过科学和社区的介绍，该项目将进一步建立对火山学、大气动力学以及这些自然现象之间复杂相互作用的兴趣，不仅在科学界，而且在学校和公众中。