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

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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.