THE MYSTERY OF MAARS: CHARACTERIZING MAAR-DIATREME VOLCANIC DEPOSITS AT HOPI BUTTES VOLCANIC FIELD (AZ) USING GIGAPAN AND THERMAL INFRARED TECHNIQUES

Maar diatreme volcanoes form when magma rises through the subsurface and interacts with groundwater causing explosive eruptions. The explosions produced in the subsurface vary in location vertically and laterally, and when they emerge the ejecta form a maar crater surrounded by a tephra ring several meters to kilometers in diameter. The maar crater is underlain by a diatreme, a carrot-shaped structure filled with a mixture of fractured host rock and magma. At the Hopi Buttes Volcanic Field (HBVF) in northern Arizona, hundreds of diatremes have become exposed as a result of erosion of the surrounding rock, in some areas up to 300 meters in depth. These exposures provide an excellent opportunity to study diatremes, as the underground eruptions are impossible to witness firsthand. The distribution of clasts by subsurface mixing and the energy of the explosions responsible, however, remain largely unconstrained due to the vertical extent of diatreme deposits, which can be hundreds of meters in height and very difficult to study and sample. Our ability to reconstruct the size, number and influence of the explosions in a maar-diatreme eruption is critical to our understanding of how they form. We present here a novel field and computer-based technique for quantitatively and qualitatively characterizing the composition and texture of maar-diatreme deposits. The technique involves use of field-based thermal infrared (TIR) imagery and visible wavelength GigaPan imagery. TIR cameras have gained popularity as tools for studying volcanic regions not only because they allow for measurement of temperature, but they also can provide compositional (spectral) information, particularly for silicate materials. The GigaPan is capable of producing high-resolution zoomable panoramic images. Using the super-resolution method presented here, TIR and GigaPan imagery of the maar-diatreme deposits are synthesized to produce very high-resolution TIR image data from which much more detailed compositional and textural information of the deposits can be acquired. Overall, the technique provides a simple and efficient method for detailed study of the deposits at HBVF, particularly those areas which are physically inaccessible, and will allow for a better understanding of the explosivity, composition, and distribution of ejecta.