| 英文摘要: | 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. |