Remote measurement of high preeruptive water vapor emissions at Sabancaya volcano by passive differential optical absorption spectroscopy

Water (H2O) is by far the most abundant volcanic volatile species and plays a predominant role in driving volcanic eruptions. However, numerous difficulties associated with making accurate measurements of water vapor in volcanic plumes have limited their use as a diagnostic tool. Here we present the first detection of water vapor in a volcanic plume using passive visible-light differential optical absorption spectroscopy (DOAS). Ultraviolet and visible-light DOAS measurements were made on 21 May 2016 at Sabancaya Volcano, Peru. We find that Sabancaya's plume contained an exceptionally high relative water vapor abundance 6 months prior to its November 2016 eruption. Our measurements yielded average sulfur dioxide (SO2) emission rates of 800–900 t/d, H2O emission rates of around 250,000 t/d, and an H2O/SO2 molecular ratio of 1000 which is about an order of magnitude larger than typically found in high-temperature volcanic gases. We attribute the high water vapor emissions to a boiling-off of Sabancaya's hydrothermal system caused by intrusion of magma to shallow depths. This hypothesis is supported by a significant increase in the thermal output of the volcanic edifice detected in infrared satellite imagery leading up to and after our measurements. Though the measurement conditions encountered at Sabancaya were very favorable for our experiment, we show that visible-light DOAS systems could be used to measure water vapor emissions at numerous other high-elevation volcanoes. Such measurements would provide observatories with additional information particularly useful for forecasting eruptions at volcanoes harboring significant hydrothermal systems

Analysis of Hot Springs in Yellowstone National Park Using ASTER and AVIRIS Remote Sensing

Data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Airborne Visible/IR Image Spectrometer (AVIRIS) were used to characterize hot spring deposits in the Lower, Midway, and Upper Geyser Basins of Yellowstone National Park from the visible/near infrared (VNIR) to thermal infrared (TIR) wavelengths. Field observations of these basins provided the critical ground truth for comparison to the remote sensing results. Fourteen study sites were selected based on diversity in size, deposit type, and thermal activity. Field work included detailed site surveys such as land cover analysis, photography, Global Positioning System (GPS) data collection, radiometric analysis, and VNIR spectroscopy. Samples of hot spring deposits, geyser deposits, and soil were also collected. Analysis of ASTER provided broad scale characteristics of the hot springs and their deposits, including the identification of thermal anomalies. AVIRIS high spectral resolution short-wave infrared (SWIR) spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral SWIR ASTER data. From the image analysis, differences in these basins were identified including the extent of thermal alteration, the location and abundance of alteration minerals, and a comparison of active, near-extinct, and extinct geysers. The activity level of each region was determined using a combination of the VNIR-SWIR-TIR spectral differences as well as the presence of elevated temperatures, detected by the TIR subsystem of ASTER. The results of this study can be applied to the exploration of extinct mineralized hydrothermal deposits on both Earth and Mars

THERMAL INFRARED ANALYSIS OF VOLCANIC PROCESSES

Due to the dangerous and remote nature of many volcanoes, field-based data collection of active processes and precursory activity is problematic. Spaceborne remote sensing instruments enable these data to be recorded, monitored, and studied. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one such sensor that currently collects data in the visible near infrared (VNIR) and thermal infrared (TIR) wavelength regions and has an archive with the highest spatial resolution TIR data (90 m) currently available to the scientific community. ASTER is capable of recording precursory volcanic activity that is unidentifiable with other sensors. By combining ASTER data with those gathered from the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS), temporal resolution is improved and processes such as the cooling rate of pyroclastic flows and subtle precursory activity are able to be quantified. Rigorous modeling of these datasets further allows results such as estimation of pyroclastic flow volume, the specific eruption mechanisms and the onset of a future eruption. The work outlined in this dissertation demonstrates how data collected from the ASTER sensor greatly improves current monitoring capabilities. New methods for processing these high spatial resolution data allow scientists to understand and better evaluate the risks associated with specific volcanoes and their common eruption styles