AdvisorHamilton, Christopher W.
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PublisherThe University of Arizona.
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AbstractI present investigations of the formation and degradation of volcanic landforms associatedwith fissure eruptions on Mars and Earth. A theme of my research is the use remote sensing data to investigate the morphology of landforms and active processes on Mars and the Earth. The morphologies of sinuous channels in Late Amazonian volcanic terrain onMars invite comparisons to channels formed by lava or water on Earth. I tested channel formation hypotheses by lava or water by conducting detailed geomorphological mapping in a region adjacent to the base of Olympus Mons. We interpreted the channels and associated fossae to be formed by alternating episodes of dike-fed fissure eruptions and groundwater release due to subsurface heating by sill emplacement. This alternating sequence of dike and sill emplacement, and associated surface eruptions of lava and water, is evidence of a complex, distributed volcanic system influenced by the tectonic stresses exerted by Olympus Mons as it continued to grow through the Amazonian Period. In a novel field study of the 2014–2015 Holuhraun fissure eruption vents in northernIceland, I created a topographic time series to measure the degradation of a large spatter rampart over the first five years post-eruption. I investigated the effects of spatter deposition on the styles and rates of erosion and found two distinct modes of topographic changes. The interior walls of the vent undergo discrete rockfall events, while the exterior slopes decrease in elevation overall, but show minimal evidence of gravitational sliding of unconsolidated scoria. The results of this study have implications for current vent landform evolution models, which predict slope changes by diffusive processes only. I propose instead a conceptual model that incorporates the probability distribution of rockfalls on the interior and diffusive processes on the exterior to better describe the earliest stages of vent erosion. I also present an analysis of the quality, precision, and accuracy of digital terrainmodels generated with stereo images from the Mars-orbiting High Resolution Imaging Science Experiment (HiRISE) camera, specifically applied to the measurement of active processes with time series of orthorectified images and digital terrain models.
Degree ProgramGraduate College