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- All Subjects: geomorphology
- Creators: Robinson, Mark S
- Creators: Schmeeckle, Mark W
Description
Impact cratering and volcanism are two fundamental processes that alter the surfaces of the terrestrial planets. Though well studied through laboratory experiments and terrestrial analogs, many questions remain regarding how these processes operate across the Solar System. Little is known about the formation of large impact basins (>300 km in diameter) and the degree to which they modify planetary surfaces. On the Moon, large impact basins dominate the terrain and are relatively well preserved. Because the lunar geologic timescale is largely derived from basin stratigraphic relations, it is crucial that we are able to identify and characterize materials emplaced as a result of the formation of the basins, such as light plains. Using high-resolution images under consistent illumination conditions and topography from the Lunar Reconnaissance Orbiter Camera (LROC), a new global map of light plains is presented at an unprecedented scale, revealing critical details of lunar stratigraphy and providing insight into the erosive power of large impacts. This work demonstrates that large basins significantly alter the lunar surface out to at least 4 radii from the rim, two times farther than previously thought. Further, the effect of pre-existing topography on the degradation of impact craters is unclear, despite their use in the age dating of surfaces. Crater measurements made over large regions of consistent coverage using LROC images and slopes derived from LROC topography show that pre-existing topography affects crater abundances and absolute model ages for craters up to at least 4 km in diameter.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
ContributorsMeyer, Heather (Author) / Robinson, Mark S (Thesis advisor) / Bell, Jim (Thesis advisor) / Denevi, Brett (Committee member) / Clarke, Amanda (Committee member) / Asphaug, Erik (Committee member) / Arizona State University (Publisher)
Created2018
Description
Worldwide, rivers and streams make up dense, interconnected conveyor belts of sediment– removing carved away earth and transporting it downstream. The propensity of alluvial river beds to self-organize into complex trains of bedforms (i.e. ripples and dunes) suggests that the associated fluid and sediment dynamics over individual bedforms are an integral component of bedload transport (sediment rolled or bounced along the river bed) over larger scales. Generally speaking, asymmetric bedforms (such as alluvial ripples and dunes) migrate downstream via erosion on the stoss side of the bedform and deposition on the lee side of the bedform. Thus, the migration of bedforms is intrinsically linked to the downstream flux of bedload sediment. Accurate quantification of bedload transport is important for the management of waters, civil engineering, and river restoration efforts. Although important, accurate qualification of bedload transport is a difficult task that continues t elude researchers. This dissertation focuses on improving our understanding and quantification of bedload transport on the two spatial scales: the bedform scale and the reach (~100m) scale.
Despite a breadth of work investigating the spatiotemporal details of fluid dynamics over bedforms and bedload transport dynamics over flat beds, there remains a relative dearth of investigations into the spatiotemporal details of bedload transport over bedforms and on a sub-bedform scale. To address this, we conducted two sets of flume experiments focused on the two fundamental regions of flow associated with bedforms: flow separation/reattachment on the lee side of the bedform (Chapter 1; backward facing-step) and flow reacceleration up the stoss side of the next bedform (Chapter 2; two-dimensional bedform). Using Laser and Acoustic Doppler Velocimetry to record fluid turbulent events and manual particle tracking of high-speed imagery to record bedload transport dynamics, we identified the existence and importance of “permeable splat events” in the region proximal to flow reattachment.
These coupled turbulent and sediment transport events are integral to the spatiotemporal pattern of bedload transport over bedforms. Splat events are localized, high magnitude, intermittent flow features in which fluid impinges on the bed, infiltrates the top portion of bed, and then exfiltrates in all directions surrounding the point of impingement. This initiates bedload transport in a radial pattern. These turbulent structures are primarily associated with quadrant 1 and 4 turbulent structures (i.e. instantaneous fluid fluctuations in the streamwise direction that bring fluid down into the bed in the case of quadrant 1 events, or up away from the bed in the case of quadrant 4 events) and generate a distinct pattern of bedload transport compared to transport dynamics distal to flow reattachment. Distal to flow reattachment, bedload transport is characterized by relatively unidirectional transport. The dynamics of splat events, specifically their potential for inducing significant magnitudes of cross-stream transport, has important implications for the evolution of bedforms from simple, two dimensional features to complex, three-dimensional features.
New advancements in sonar technology have enabled more detailed quantification of bedload transport on the reach scale, a process paramount to the effective management of rivers with sand or gravel-dominated bed material. However, a practical and scalable field methodology for reliably estimating bedload remains elusive. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time-series of bed elevation profiles (BEPs) acquired using echosounders. Using two sets of repeat multibeam sonar surveys from the Diamond Creek USGS gage station in Grand Canyon National Park with large spatio-temporal resolution and coverage, we compute bedload using three field techniques for acquiring BEPs: repeat multi-, single-, and multiple single-beam sonar. Significant differences in flux arise between repeat multibeam and single beam sonar. Mulitbeam and multiple single beam sonar systems can potentially yield comparable results, but the latter relies on knowledge of bedform geometries and flow that collectively inform optimal beam spacing and sampling rate. These results serve to guide design of optimal sampling, and for comparing transport estimates from different sonar configurations.
Despite a breadth of work investigating the spatiotemporal details of fluid dynamics over bedforms and bedload transport dynamics over flat beds, there remains a relative dearth of investigations into the spatiotemporal details of bedload transport over bedforms and on a sub-bedform scale. To address this, we conducted two sets of flume experiments focused on the two fundamental regions of flow associated with bedforms: flow separation/reattachment on the lee side of the bedform (Chapter 1; backward facing-step) and flow reacceleration up the stoss side of the next bedform (Chapter 2; two-dimensional bedform). Using Laser and Acoustic Doppler Velocimetry to record fluid turbulent events and manual particle tracking of high-speed imagery to record bedload transport dynamics, we identified the existence and importance of “permeable splat events” in the region proximal to flow reattachment.
These coupled turbulent and sediment transport events are integral to the spatiotemporal pattern of bedload transport over bedforms. Splat events are localized, high magnitude, intermittent flow features in which fluid impinges on the bed, infiltrates the top portion of bed, and then exfiltrates in all directions surrounding the point of impingement. This initiates bedload transport in a radial pattern. These turbulent structures are primarily associated with quadrant 1 and 4 turbulent structures (i.e. instantaneous fluid fluctuations in the streamwise direction that bring fluid down into the bed in the case of quadrant 1 events, or up away from the bed in the case of quadrant 4 events) and generate a distinct pattern of bedload transport compared to transport dynamics distal to flow reattachment. Distal to flow reattachment, bedload transport is characterized by relatively unidirectional transport. The dynamics of splat events, specifically their potential for inducing significant magnitudes of cross-stream transport, has important implications for the evolution of bedforms from simple, two dimensional features to complex, three-dimensional features.
New advancements in sonar technology have enabled more detailed quantification of bedload transport on the reach scale, a process paramount to the effective management of rivers with sand or gravel-dominated bed material. However, a practical and scalable field methodology for reliably estimating bedload remains elusive. A popular approach involves calculating transport from the geometry and celerity of migrating bedforms, extracted from time-series of bed elevation profiles (BEPs) acquired using echosounders. Using two sets of repeat multibeam sonar surveys from the Diamond Creek USGS gage station in Grand Canyon National Park with large spatio-temporal resolution and coverage, we compute bedload using three field techniques for acquiring BEPs: repeat multi-, single-, and multiple single-beam sonar. Significant differences in flux arise between repeat multibeam and single beam sonar. Mulitbeam and multiple single beam sonar systems can potentially yield comparable results, but the latter relies on knowledge of bedform geometries and flow that collectively inform optimal beam spacing and sampling rate. These results serve to guide design of optimal sampling, and for comparing transport estimates from different sonar configurations.
ContributorsLeary, Kate (Author) / Schmeeckle, Mark W (Thesis advisor) / Whipple, Kelin X (Thesis advisor) / Heimsath, Arjun (Committee member) / Walker, Ian (Committee member) / Arrowsmith, Ramon (Committee member) / Arizona State University (Publisher)
Created2018
Description
Previous workers hypothesized that lunar Localized Pyroclastic Deposits (LPDs) represent products of vulcanian-style eruptions, since some have low proportions of juvenile material. The objective of the first study is to determine how juvenile composition, calculated using deposit and vent volumes, varies among LPDs. I used Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) digital terrain models (DTMs) to generate models of pre-eruption surfaces for 23 LPDs and subtracted them from the NAC DTMs to calculate deposit and vent volumes. Results show that LPDs have a wide range of juvenile compositions and thinning profiles, and that there is a positive relationship between juvenile material proportion and deposit size. These findings indicate there is greater diversity among LPDs than previously understood, and that a simple vulcanian eruption model may only apply to the smallest deposits.
There is consensus that martian outflow channels were formed by catastrophic flooding events, yet many of these channels exhibit lava flow features issuing from the same source as the eroded channels, leading some authors to suggest that lava may have served as their sole agent of erosion. This debate is addressed in two studies that use Context Camera images for photogeologic analysis, geomorphic mapping, and cratering statistics: (1) A study of Mangala Valles showing that it underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian, consistent with alternating episodes of flooding and volcanism. (2) A study of Maja Valles finds that it is thinly draped in lava flows sourced from Lunae Planum to the west, rendering it analogous to the lava-coated Elysium outflow systems. However, the source of eroded channels in Maja Valles is not the source of the its lava flows, which instead issue from south Lunae Planum. The failure of these lava flows to generate any major channels along their path suggests that the channels of Maja Valles are not lava-eroded.
Finally, I describe a method of locating sharp edges in out-of-focus images for application to automated trajectory control systems that use images from fixed-focus cameras to determine proximity to a target.
There is consensus that martian outflow channels were formed by catastrophic flooding events, yet many of these channels exhibit lava flow features issuing from the same source as the eroded channels, leading some authors to suggest that lava may have served as their sole agent of erosion. This debate is addressed in two studies that use Context Camera images for photogeologic analysis, geomorphic mapping, and cratering statistics: (1) A study of Mangala Valles showing that it underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian, consistent with alternating episodes of flooding and volcanism. (2) A study of Maja Valles finds that it is thinly draped in lava flows sourced from Lunae Planum to the west, rendering it analogous to the lava-coated Elysium outflow systems. However, the source of eroded channels in Maja Valles is not the source of the its lava flows, which instead issue from south Lunae Planum. The failure of these lava flows to generate any major channels along their path suggests that the channels of Maja Valles are not lava-eroded.
Finally, I describe a method of locating sharp edges in out-of-focus images for application to automated trajectory control systems that use images from fixed-focus cameras to determine proximity to a target.
ContributorsKeske, Amber (Author) / Christensen, Philip R. (Thesis advisor) / Robinson, Mark S (Committee member) / Clarke, Amanda B (Committee member) / Whipple, Kelin X (Committee member) / Bell, James F. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Gnamma pit is an Australian aboriginal term for weathering pit. A mix of weathering and aeolian processes controls the formation of gnamma pits. There is a potential to utilize gnamma as an indicator of paleowind intensity because gnamma growth is promoted by the removal of particles from gnamma pits by wind, a process referred to as deflation. Wind tunnel tests determining the wind velocity threshold of deflation over a range of pit dimensions and particles sizes are conducted. Computational fluid dynamics (CFD) modeling utilizing the Re-Normalisation Group (RNG) K-Epsilon turbulence closure is used to investigate the distribution of wall shear stress and turbulent kinetic energy. An empirical equation is proposed to estimate shear stress as a function of the wind velocity and pit depth dimensions. With this equation and Shields Diagram, the wind velocity threshold for evacuating particles in the pit can be estimated by measuring the pit depth ratio and particle size. It is expected that the pit would continue to grow until this threshold is reached. The wind speed deflation threshold is smaller in the wind tunnel than predicted by the CFD and Shields diagram model. This discrepancy may be explained by the large turbulent kinetic energy in the gnamma pit as predicted by the CFD model as compared to the flat bed experiments used to define the Shields diagram. An empirical regression equation of the wind tunnel data is developed to estimate paleowind maximums.
ContributorsWang, Yinlue (Author) / Schmeeckle, Mark W (Thesis advisor) / Dorn, Ronald I. (Committee member) / Balling, Robert C. (Committee member) / Arizona State University (Publisher)
Created2015
Description
Anthropogenic activities have had a profound effect on ecosystems, sediment budgets, and dust emissions stemming from widespread changes in land use and land cover and increases in sediment disturbance. Sandy coastal environments are under increasing pressure from the impacts of rising sea levels, coastal flooding, and erosion. Coastal foredunes can serve as a buffer to protect coastal communities from the impacts of coastal erosion, flooding, and sea-level rise. They also serve an important role as an ecosystem service, providing opportunities for recreation (off-highway vehicle, hiking, tourism) and habitat for native and endemic biota. Increased disturbance and pressure by human activity within the beach-dune system can lead to a decoupling of form and function from natural geomorphic and biotic processes. Dune management and restoration is often employed to mitigate some of the aforementioned pressures. Dynamic or ‘nature-based’ restoration aims to restore the form and function of a geomorphic system and improve landform resilience to external pressures by employing complimentary native plant species. This type of approach places emphasis on the ecological and geomorphic interactions within a landscape to improve the overall function and resiliency of the system to external pressures. Two case studies along the coast of California, the Lanphere Dunes and Oceano Dunes, provide uniquely different approaches to foredune restoration and the corresponding issues of landscape management for various goals. The case studies provided employ a suite of close-range remote sensing techniques, including kite aerial photography, uncrewed aerial systems photography, and terrestrial laser scanning, to generate high resolution (< 0.1 m) products (surface models; orthophoto mosaics in red-green-blue (RGB) and multispectral) to quantify and inform on restoration efforts by examining sediment budget and vegetation characteristics over a mesoscale (spatial and temporal). Results were compared to a variety of control sites (e.g., no restoration, natively vegetated, invasively vegetated) to highlight the differences between restored and unrestored landscapes, and the efficacy of restoration efforts for improving the developmental trajectory of a landscape towards a "desired" state.
ContributorsHilgendorf, Zach (Author) / Walker, Ian J (Thesis advisor) / Dorn, Ronald I (Committee member) / Schmeeckle, Mark W (Committee member) / Arizona State University (Publisher)
Created2022
Description
Western Utopia Planitia, located in the northern plains of Mars, is home to a myriad of possible periglacial landforms. One of these is scalloped depressions, defined primarily by their oval-shape and north-south asymmetry, including both pole-facing “steps” and an equator-facing slope. Scalloped depressions are thought to have formed through sublimation of ground ice in the Late Amazonian, consistent with the hypothesis that Mars is presently in an interglacial period marked by the poleward retreat of mid-latitudinal ice. The directional growth of scalloped depressions was mapped within the region and present a correlation between topography and scalloped depression development. It was determined that topography appears to play a role in scallop development, as noted by the most-densely scalloped region residing among a lower spatial density of craters previously mapped by Harrison et al. (2019). Within this region, scallops were also observed to be absent atop crater ejecta, but present atop crater ejecta in other regions of the study area. A large majority of scallops maintain a north-south asymmetry and observed changes in geomorphology that range from predominantly smoother terrain in the northern latitudes to very hummocky terrain dominated by possible periglacial features as latitude decreases. Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) images were primarily used, with a few images coming from the MRO High Resolution Imaging Science Experiment (HiRISE). Observations are consistent with previous studies showing the overall density of scalloped depressions decreases with increasing latitude, with the majority exhibiting steps facing in a poleward direction. The majority of scallops observed to have steps in a non-poleward direction occur within in ice-rich regions mapped by Stuurman et al. (2016). It was ultimately concluded that scallops demonstrating poleward-facing steps likely formed during periods of high obliquity on Mars in the Late Amazonian, while scallops within the ice-rich regions potentially formed at a greater range of obliquities.
ContributorsTognetti, Laurence (Author) / Bell Iii, James F (Thesis advisor) / Robinson, Mark S (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2019
Description
Rock traits (grain size, shape, orientation) are fundamental indicators of geologic processes including geomorphology and active tectonics. Fault zone evolution, fault slip rates, and earthquake timing are informed by examinations of discontinuities in the displacements of the Earth surface at fault scarps. Fault scarps indicate the structure of fault zones fans, relay ramps, and double faults, as well as the surface process response to the deformation and can thus indicate the activity of the fault zone and its potential hazard. “Rocky” fault scarps are unusual because they share characteristics of bedrock and alluvial fault scarps. The Volcanic Tablelands in Bishop, CA offer a natural laboratory with an array of rocky fault scarps. Machine learning mask-Region Convolutional Neural Network segments an orthophoto to identify individual particles along a specific rocky fault scarp. The resulting rock traits for thousands of particles along the scarp are used to develop conceptual models for rocky scarp geomorphology and evolution. In addition to rocky scarp classification, these tools may be useful in many sedimentary and volcanological applications for particle mapping and characterization.
ContributorsScott, Tyler (Author) / Arrowsmith, Ramon (Thesis advisor) / Das, Jnaneshwar (Committee member) / DeVecchio, Duane (Committee member) / Arizona State University (Publisher)
Created2020