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Item Hydrogen production from mechanically-activated basalt under experimental conditions simulating subglacial environments(Montana State University - Bozeman, College of Letters & Science, 2019) Mitchell, Kari Rebecca; Chairperson, Graduate Committee: Mark L. SkidmoreShearing of rocks containing silicate followed by reaction with water has previously been shown to produce hydrogen under experimental conditions relevant to subglacial environments. The abiotic production of hydrogen, carbon dioxide, methane, and other hydrocarbon gases has also been demonstrated in laboratory comminution experiments on rocks from glaciated catchments. Thus, the generation of these biologically useful gases (e.g. hydrogen and methane) beneath glaciers could serve as a source of reductant capable of sustaining microbial ecosystems beneath the ice. Despite the ubiquitous nature of basalt on both Earth and other planetary bodies, production of hydrogen and other gases from basalt through mechanical shearing and reaction with water has not been demonstrated. Basalts were collected from glaciated catchments in Iceland to test whether hydrogen and other gases were produced under laboratory conditions simulating glacial comminution. Rock samples were milled under an inert atmosphere, after which water was added and hydrogen and methane production measured over time. An average of 6.6 nmol hydrogen and 2.6 nmol methane per gram rock were produced after 168 hours from basalt samples tested; additionally, hydrogen peroxide and radicals were produced during grinding. The abiogenic production of hydrogen and methane under these simulated subglacial basaltic environments demonstrated in this study also has implications for supporting subglacial microbial communities during periods of extended glaciation, such as glacial-interglacial cycles in the Pleistocene and during the pervasive low-latitude glaciation of the Cryogenian. This mechanism of hydrogen production also has implications for the potential for life on icy worlds like Mars.Item Glacial effects on stream water nitrate: an examination of paired catchments in southern Montana(Montana State University - Bozeman, College of Letters & Science, 2019) Allen, Jordan Jon; Chairperson, Graduate Committee: Mark L. Skidmore and Jean Dixon (co-chair)Nitrogen is frequently a limiting nutrient in biologic systems. Previous research on alpine streams and lakes in the Beartooth Mountains, Montana/Wyoming has demonstrated nitrate concentrations in waters draining glaciated catchments that are up to ten times greater than comparable adjacent non-glaciated catchments. The enhanced nitrate concentrations in the glacial fed lakes have been associated with increased diatom abundance relative to the snow fed-lakes. However, the source of the enhanced nitrate input remained undetermined, as well as how nitrate concentrations vary temporally during summer melt. This study measured concentrations of nitrate and ammonium and the isotopic composition of nitrate over the 2016 melt-season in a paired catchment system, in the Beartooth Mountains, Montana. The two catchments have similar elevations, atmospheric inputs, bedrock geology, area, and contain lakes, however, one catchment contains a glacier, the other does not. The stream waters in the glaciated catchment showed significantly elevated nitrate concentrations relative to those in the non-glaciated catchment and to catchment atmospheric input, as determined by snowpack nitrate concentrations. Nitrate concentrations in the glacial stream were observed to increase both temporally as the melt-season progressed, and spatially, with distance downstream from the glacier terminus. Ammonium concentrations in the glacial stream were highest close to the glacier terminus, declining with distance downstream, but also increasing during the melt season. Nitrate isotopic values distinguish the stream waters from atmospheric inputs indicating additional nitrate sources in the catchment. Potential additional sources include inorganic nitrogen released from bedrock sources and microbially fixed nitrogen. Abiotic laboratory weathering experiments simulating subglacial conditions reacted deionized water with finely milled bedrock at 4°C, and a modest quantity of ammonium was released. Potassium is often replaced by ammonium in minerals. Rocks from the study area contained ~3% potassium by weight. Ammonium could then be converted to nitrate through microbial processes within the proglacial environment adding to the atmospheric nitrate input to the stream nitrate budget. However, estimated rates of sediment production, and by inference ammonium production, cannot account for the observed nitrate concentrations and flux, indicating an additional nitrate source, which is most likely ultimately derived from microbial nitrogen fixation.Item Landslide morphology and its insight into the timing and causes of slope failure: case study of post-glacial landslides in Yellowstone National Park(Montana State University - Bozeman, College of Letters & Science, 2018) Nicholas, Grace Ellen; Chairperson, Graduate Committee: Jean DixonLandslides are ubiquitous to post-glacial landscapes worldwide. Withdrawal of glacier ice exposes over-steepened landscapes that may be unstable, and consequently susceptible to landsliding. Glacial debuttressing may directly destabilize slopes; however, seismicity and transitions to interglacial climates associated with greater effective moisture and subsequent degradation of permafrost may also play a role. Here, we explore disparate potential mechanisms of slope failure in a set of post-glacial landslides in northwest Yellowstone National Park. We quantify spatial relationships, topographic metrics, and relative age of eight landslides within the north entrance to the park, a system traversed by over 700,000 visitors every year. Analysis of high-resolution topography indicates increasing surface roughness of non-active landslides southward. These roughness values in ancient slides are roughly half those of the active Slide Lake Landslide, and suggest younging ages along the retreat path of the Yellowstone Ice Cap, consistent with glacial debutressing as the likely trigger for these slides. However, roughness values and their application for relative age dating are strongly confounded by topographic biases such as gullying, fluvial erosional contacts, and anthropogenic features (e.g., roads, structures). Once roughness biases are removed, we find roughness differences between landslides decrease, and do not support younging ages along the path of ice retreat. Thus, glacial debuttressing most likely only had a preparatory influence on slope failure, and was not the direct trigger. Analysis of subsurface soils at landslide toes indicate a >17 plasticity index, pointing to highly expansive clays that are sensitive to moisture addition. Stratigraphic relationships between post-glacial terraces and soil analyses suggest a late Pleistocene (~13 - 11.5 ka) timing for slide initiation, a period coincident with high available moisture. Stream power analysis indicates that Holocene incision of the Gardiner River is focused at a knickpoint locally coincident with the toe of the active Slide Lake Landslide, providing a mechanism for modern, local reactivation of the ancient slides. Together, our findings broadly show how quantifying the temporal and spatial patterns of landslides can be diagnostic of the controls on slope failure, and can be used to understand risk. They also highlight the importance of careful site calibrations and bias removals in roughness analysis.Item Modeling mass balance at Robertson Glacier, Alberta, Canada 1912-2012(Montana State University - Bozeman, College of Letters & Science, 2017) Scanlon, Ryan Scott; Chairperson, Graduate Committee: Mark L. Skidmore; Jordy Hendrikx (co-chair)Glacier mass balance is important to study due to the role of glaciers in the hydrological cycle. Glacier mass balance is typically difficult to measure without numerous in situ measurements and monitoring over the course of many years. Physically based melt models are a good tool for estimating melt using temperature, solar radiation, and albedo and are used extensively in this thesis. A Degree Day (DD) model and an Enhanced Temperature Index (ETI) model are used to model mass balance for Robertson Glacier, Alberta, Canada during the period 1912-2012. The DD model only incorporates temperature, while the ETI model incorporates temperature, incoming solar radiation, and albedo. Incoming solar radiation was modeled for the period 2007-2012 and parameterized for the period 1912-2006 while temperature was measured at the regional scale and synthesized for Robertson Glacier and the snowpack thickness was modeled using PRISM. The DD and ETI models both assume a static ice mass, i.e. no flow or change in ice elevation due to mass loss over the century time period. Both models estimate a high value of annual and accumulated mean mass loss for the period 1912-2012. Sensitivity analyses of model inputs indicate that snowpack is an important factor, and it appears PRISM estimates may underrepresent beginning of the year snowpack by 220% based on a comparison of modelled to measured values on the adjacent Haig Glacier. Avalanching is not a key component of accumulation on the Haig Glacier but is a key process at Robertson Glacier, and could result in locally doubling the snowpack accumulation in avalanche zones. These factors including the resultant albedo changes with a thicker snowpack are all part of a compounding negative feedback cycle on glacier mass loss. In summary, the thesis has highlighted several potential limitations to the ETI and DD models for assessing mass loss for a small mountain glacier in the southern Canadian Rockies and provides suggestions for future modelling work in this region.Item Methane flux from recently exposed subglacial sediments, Robertson Glacier, Canada(Montana State University - Bozeman, College of Letters & Science, 2014) Spotts, Terra Marie; Chairperson, Graduate Committee: Mark L. SkidmoreMethane is over 20 times more effective than CO 2 as a greenhouse gas. Thus, its atmospheric concentration and the processes controlling it are important components of the global climate system. Recent research has shown methanogenesis in subglacial sediments. However, the net contribution from subglacial systems to the global methane budget is poorly understood due to a dearth of empirical data. Using measurements via the static chamber method, the flux of methane from recently exposed subglacial sediments at Robertson Glacier, Canadian Rockies was quantified. Methane concentrations were measured from surface gas flux chambers in transects both parallel and perpendicular to the glacier terminus. Over 300 measurements were made during the 2012 melt season (July to September) and used to determine both spatial and temporal variability in the gas fluxes. The chamber farthest from the glacier terminus, approximately 50 m down valley, had an average flux close to zero whereas the chambers nearest the terminus had the highest average fluxes. The average methane efflux from the sediment surface to atmosphere was 0.22 micromoles m -2 d -1. The highest methane efflux during the season, 11.0 micromoles m -2 d -1, was measured in close proximity to the glacier terminus. Shallow sediment cores were collected adjacent to the static chambers and vertical gas concentration profiles were measured from the cores. Within the profiles, methane concentrations were greater than atmospheric concentrations at all depths. Additionally, CO 2, CO and H 2 gas concentrations were analyzed in the cores to evaluate potential microbial metabolic pathways of methane production. Previous studies on methane fluxes from glacial sediments in Greenland and the Swiss Alps used single time point flux measurements during a melt season from multiple locations. This study concludes that such point measurements are unlikely representative for determining a net seasonal flux as they do not consider temporal variability. There was a two order of magnitude difference between the annual source contribution of methane based on the average melt season flux and the highest measured surface flux. This indicates that single sampling periods may significantly over or underestimate the net seasonal flux of methane from recently exposed glacial sediments to the atmosphere.Item Quaternary glacial geology and geomorphology of the Teton drainage area, Teton County, Montana(Montana State University - Bozeman, College of Letters & Science, 1968) Chalmers, Ann LeslieItem Late Pleistocene glacier dynamics of southwestern Montana and adjacent Idaho and paleoclimatic implications(Montana State University - Bozeman, College of Letters & Science, 1989) Murray, Donald R.Item Temporal and spatial relations of late Quaternary valley and piedmont glaciers in Tom Miner Basin, Montana(Montana State University - Bozeman, College of Letters & Science, 1993) Vandeberg, Gregory ScottItem East Rock Glacier of Lone Mountain, Madison County, Montana(Montana State University - Bozeman, College of Letters & Science, 1972) Goolsby, JimItem Ice movement and structural characteristics of the Cathedral Glacier system, Atlin Provincial Park, British Columbia(Montana State University - Bozeman, College of Letters & Science, 1983) Johnson, Ronald Frederick