Emission Spectroscopy of Silicic Lavas: Implications for Dome Processes and Hazards

拉姆齐对硅质熔岩穹隆的爆炸性减压，由于过陡和/或流动前锋坍塌，可能会产生中等到大量的火山碎屑流。在过去十年中，这类事件在日本苏弗里尔山、蒙特塞拉特和云顶等火山造成了大量人员伤亡和财产损失。对圆顶表面发射的热红外(TIR)能量进行详细检查，可以提供有关熔岩成分和微米级表面结构的定量数据。例如，玻璃状熔岩中表面小泡的百分比往往会使发射率吸收带的光谱对比度变暗或降低，与其表面丰度成线性比例。这一导出的参数为穹顶的就位/演化提供了重要的见解，并且与温度和表面变形相结合，对穹顶的危险状态有直接的影响。发射光谱与傅里叶变换红外(FTIR)显微镜的不同之处在于，它适用于捕捉全岩石样品、宏观表面结构和遥感应用的信息。然而，为了提供必要的严格和定量的分析以确信地解释这些数据，提出了两个目标：(1)对各种成分的玻璃熔岩进行详细的实验室分析，这将使红外光谱特征与化学成分和结构形态之间有定量的联系；(2)将这项研究扩大到对蒙特塞拉特苏弗里尔山火山穹顶的实地研究和对俄罗斯贝兹明尼火山穹顶的遥感研究。这种对活动穹隆的应用将把熔岩中的化学变化与来自实验室研究的结构信息联系起来。它还提供了实验室分析/比例尺与空间分析/比例尺之间的重要桥梁。这项研究的学术价值在于对天然矿物和岩石玻璃的热红外发射进行了更完整的分析和理论分析。这反过来又将提供对主动穹顶安置过程和监测的联系的准确了解。该项目的更广泛影响包括对一名研究生、一名来自代表性不足的地理群体的博士后研究员和几名本科生进行实验室、计算机和实地培训。此外，这些结果将促进对富含玻璃/泡囊样品的发射光谱的科学理解。这一知识有可能导致开发一种新的空间和地面科学工具，该工具可用于监测活跃穹顶的形成过程及其随后的潜在危险。

EAR-0309631Ramsey Explosive decompression of silicic lava domes due to over-steepening and/or flow front collapse can produce moderate to large pyroclastic flows. Such events have resulted in numerous casualties and property damage in the past decade at volcanoes such as Soufriere Hills, Montserrat and Unzen, Japan. The detailed examination of thermal infrared (TIR)-emitted energy from a dome's surface can provide quantitative data on the composition and micrometer-scale surface texture of the lava. For example, the percentage of surface vesicles in glassy lavas tends to mute or reduce the spectral contrast of the emissivity absorption bands in linear proportion to their surface abundance. This derived parameter has provided important insights into dome emplacement/evolution, and where coupled with temperature and surface deformation, has direct implications for the hazard state of the dome. Emission spectroscopy differs from Fourier-transform infrared (FTIR) microscopy in its applicability to capture information on whole rock samples, macroscopic surface textures and remote sensing applications. However, in order to provide the rigorous and quantitative analysis needed to confidently interpret these data, two objectives are proposed: (1) to perform a detailed laboratory-based analysis of glassy lavas of various compositions, which will result in a quantitative correlation between infrared spectral features and the chemical composition and textural morphology; and (2) extend that research to both a field-based study of the Soufriere Hills volcanic dome, Montserrat and a remote sensing-based study of the Bezymianny volcanic dome, Russia. This application to active domes will relate the chemical variation in the lavas to textural information derived from the laboratory studies. It also provides a critical bridge between the laboratory analysis/scale and those derived from space. The intellectual merit of the research is a more complete analytical and theoretical analysis of the thermal infrared emission of naturally occurring mineral and rock glasses. This in turn will provide an accurate understanding of the linkages to active dome emplacement processes and monitoring. The broader implications of this project include laboratory, computer and field training of one graduate student, one post-doctoral researcher from an under-represented geographical group, and several undergraduate students. In addition, the results will advance the scientific understanding of emission spectroscopy acquired from glass/vesicle-rich samples. That knowledge has the potential to lead to the development of a new space and ground-based scientific tool, which can be used to monitor the processes of active dome formation and its subsequent hazard potential.