Monitoring the Surface Changes and Growth of the Soufriére Hills Lava Dome: Thermal Infrared Analyses of Field and Spaceborne Data

The Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) is the only high resolution multispectral thermal infrared (TIR) imager currently in Earth-orbit. The data being returned are ideal for discerning physical variations on the surface of active lava domes such as Soufriére Hills, Montserrat. The 90 meter spatial resolution of the TIR data provides accurate measurements of the surface temperature and emissivity. This information can be used to map the glass, vesicle and petrological distribution on the dome's surface, and therefore provide fundamental insights into lava emplacement processes. For this study, six nighttime ASTER scenes of the dome and surrounding region captured over the past two years were chosen. These images show the entire dome, are relatively cloud-free and have significant thermal anomalies present, including summit and pyroclastic flow deposits. In order to validate the image data, detailed field-based information was collected including temperature, GPS and spectroscopic data (similar to the ASTER spectral band passes). In addition, a searchable database of activity based on Montserrat Volcano Observatory (MVO) reports has been created and used as a framework for the image data. Field measurements were taken in conjunction with a nighttime overpass of ASTER. Active areas were determined both visually and with the aid of high resolution radiometers. The heightened activity precluded close field measurements; therefore, long range laser profiling and GPS were used to locate anomalies on the dome surface. A CIMEL spectro-radiometer with identical TIR wavelengths to ASTER and a FRIR were used to map surface temperature and spectral variations. Numerous target areas were chosen including spines, lobes, incandescence, and fresh pyroclastic deposits. Samples of the most recent pyroclastic deposits have been collected and are being analyzed for mineral, phenocryst, and vesicle content using both petrographic and infrared analyses. This is the most detailed suite of thermal infrared data collected at an active silicic dome and is providing a more complete understanding of the capabilities of remotely acquired TIR data to accurately describe active dome processes. This approach can easily be applied to other active areas that have the potential of transitioning from effusive to explosive dome growth, subsequent collapse and ensuing pyroclastic activity.