Matching Items (93)
Description
Identifying space resources is essential to establish an off-Earth human presence on the Moon, Mars, and beyond. One method for determining the composition and mineralogy of planetary surfaces is thermal infrared emission spectroscopy. I investigated this technique as a potential tool to explore for magmatic Ni-Cu±PGE sulfide deposits by producing and measuring a 100% sulfide (pyrrhotite) sample derived from the Stillwater Complex. Pyrrhotite violates key assumptions used to calibrate thermal infrared emission data, making extraterrestrial sulfides “appear colder” than their actual physical temperature, and their spectra will contain a negative slope. To derive the absolute emissivity of graybody minerals more accurately, I developed a new measurement technique, which demonstrates that pyrrhotite is spectrally featureless in the mid-infrared and has a maximum emissivity of ~0.7. Magmatic sulfide deposits are commonly associated with silicates. Thus, emissivity spectra of sulfide/silicate mixtures were acquired to further understand how sulfide prospecting would be conducted on rocky bodies such as Mars. I demonstrate that as sulfide increases, the apparent brightness temperature decreases linearly and, if left unaccounted for, will contribute a negative spectral slope in their emissivity spectra. The presence of sulfide also reduces the magnitude of all the silicate’s diagnostic spectral features, which is linear as sulfide increases. A linear retrieval algorithm was also applied to the mixture spectra, demonstrating that sulfide could be detected at abundances of ≥10 modal %.
The main resource being targeted for mining on the Moon is water ice. Thus, a mining map tool of the Lunar South Pole that incorporates temperature, illumination, Earth visibility, and slope data was developed to identify the most suitable locations for water ice mining and establishing bases for operations. The map is also used to assess the mining potential of the Artemis III candidate landing regions. Finally, space mining must be governed, but no framework has yet to be established. I propose a governance structure, notification system, contract system, best mining practices, and area-based environmental regulations to manage water ice mining activities. The Lunar Mining Map Tool’s block system is used as a spatial planning tool to administer the governance framework and facilitate management.
ContributorsHubbard, Kevin M (Author) / Elkins-Tanton, Linda T (Thesis advisor) / Christensen, Philip R (Committee member) / Semken, Steven (Committee member) / Sharp, Thomas (Committee member) / O'Rourke, Joseph G (Committee member) / De Zwart, Melissa (Committee member) / Arizona State University (Publisher)
Created2023
Description
The inductance of a conductor expresses its tendency to oppose a change in current flowing through it. For superconductors, in addition to the familiar magnetic inductance due to energy stored in the magnetic field generated by this current, kinetic inductance due to inertia of charge carriers is a significant and often dominant contribution to total inductance. Devices based on modifying the kinetic inductance of thin film superconductors have widespread application to millimeter-wave astronomy. Lithographically patterning such a film into a high quality factor resonator produces a high sensitivity photodetector known as a kinetic inductance detector (KID), which is sensitive to frequencies above the superconducting energy gap of the chosen material. Inherently multiplexable in the frequency domain and relatively simple to fabricate, KIDs pave the way to the large format focal plane array instruments necessary to conduct the next generation of cosmic microwave background (CMB), star formation, and galaxy evolution studies. In addition, non-linear kinetic inductance can be exploited to develop traveling wave kinetic inductance parametric amplifiers (TKIPs) based on superconducting delay lines to read out these instruments.
I present my contributions to both large and small scale collaborative efforts to develop KID arrays, spectrometers integrated with KIDs, and TKIPs. I optimize a dual polarization TiN KID absorber for the next generation Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry, which is designed to investigate the role magnetic fields play in star formation. As part of an effort to demonstrate aluminum KIDs on sky for CMB polarimetry, I fabricate devices for three design variants. SuperSpec and WSpec are respectively the on-chip and waveguide implementations of a filter bank spectrometer concept designed for survey spectroscopy of high redshift galaxies. I provide a robust tool for characterizing the performance of all SuperSpec devices and demonstrate basic functionality of the first WSpec prototype. As part of an effort to develop the first W-Band (75-110 GHz) TKIP, I construct a cryogenic waveguide feedthrough, which enhances the Astronomical Instrumentation Laboratory’s capability to test W-Band devices in general. These efforts contribute to the continued maturation of these kinetic inductance technologies, which will usher in a new era of millimeter-wave astronomy.
I present my contributions to both large and small scale collaborative efforts to develop KID arrays, spectrometers integrated with KIDs, and TKIPs. I optimize a dual polarization TiN KID absorber for the next generation Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry, which is designed to investigate the role magnetic fields play in star formation. As part of an effort to demonstrate aluminum KIDs on sky for CMB polarimetry, I fabricate devices for three design variants. SuperSpec and WSpec are respectively the on-chip and waveguide implementations of a filter bank spectrometer concept designed for survey spectroscopy of high redshift galaxies. I provide a robust tool for characterizing the performance of all SuperSpec devices and demonstrate basic functionality of the first WSpec prototype. As part of an effort to develop the first W-Band (75-110 GHz) TKIP, I construct a cryogenic waveguide feedthrough, which enhances the Astronomical Instrumentation Laboratory’s capability to test W-Band devices in general. These efforts contribute to the continued maturation of these kinetic inductance technologies, which will usher in a new era of millimeter-wave astronomy.
ContributorsChe, George (Author) / Mauskopf, Philip D (Thesis advisor) / Aberle, James T., 1961- (Committee member) / Groppi, Christopher (Committee member) / Semken, Steven (Committee member) / Trichopoulos, Georgios (Committee member) / Arizona State University (Publisher)
Created2018
Description
Aquifers host the largest accessible freshwater resource in the world. However, groundwater reserves are declining in many places. Often coincident with drought, high extraction rates and inadequate replenishment result in groundwater overdraft and permanent land subsidence. Land subsidence is the cause of aquifer storage capacity reduction, altered topographic gradients which can exacerbate floods, and differential displacement that can lead to earth fissures and infrastructure damage. Improving understanding of the sources and mechanisms driving aquifer deformation is important for resource management planning and hazard mitigation.
Poroelastic theory describes the coupling of differential stress, strain, and pore pressure, which are modulated by material properties. To model these relationships, displacement time series are estimated via satellite interferometry and hydraulic head levels from observation wells provide an in-situ dataset. In combination, the deconstruction and isolation of selected time-frequency components allow for estimating aquifer parameters, including the elastic and inelastic storage coefficients, compaction time constants, and vertical hydraulic conductivity. Together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation. Understanding aquifer parameters is useful for the ongoing management of groundwater resources.
Case studies in Phoenix and Tucson, Arizona, focus on land subsidence from groundwater withdrawal as well as distinct responses to artificial recharge efforts. In Christchurch, New Zealand, possible changes to aquifer properties due to earthquakes are investigated. In Houston, Texas, flood severity during Hurricane Harvey is linked to subsidence, which modifies base flood elevations and topographic gradients.
Poroelastic theory describes the coupling of differential stress, strain, and pore pressure, which are modulated by material properties. To model these relationships, displacement time series are estimated via satellite interferometry and hydraulic head levels from observation wells provide an in-situ dataset. In combination, the deconstruction and isolation of selected time-frequency components allow for estimating aquifer parameters, including the elastic and inelastic storage coefficients, compaction time constants, and vertical hydraulic conductivity. Together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation. Understanding aquifer parameters is useful for the ongoing management of groundwater resources.
Case studies in Phoenix and Tucson, Arizona, focus on land subsidence from groundwater withdrawal as well as distinct responses to artificial recharge efforts. In Christchurch, New Zealand, possible changes to aquifer properties due to earthquakes are investigated. In Houston, Texas, flood severity during Hurricane Harvey is linked to subsidence, which modifies base flood elevations and topographic gradients.
ContributorsMiller, Megan Marie (Author) / Shirzaei, Manoochehr (Thesis advisor) / Reynolds, Stephen (Committee member) / Tyburczy, James (Committee member) / Semken, Steven (Committee member) / Werth, Susanna (Committee member) / Arizona State University (Publisher)
Created2018
Description
The search for life on Mars is a major NASA priority. A Mars Sample Return
(MSR) mission, Mars 2020, will be NASA's next step towards this goal, carrying an instrument suite that can identify samples containing potential biosignatures. Those samples will be later returned to Earth for detailed analysis. This dissertation is intended to inform strategies for fossil biosignature detection in Mars analog samples targeted for their high biosignature preservation potential (BPP) using in situ rover-based instruments. In chapter 2, I assessed the diagenesis and BPP of one relevant analog habitable Martian environment: a playa evaporite sequence within the Verde Formation, Arizona. Coupling outcrop-scale observations with laboratory analyses, results revealed four diagenetic pathways, each with distinct impacts on BPP. When MSR occurs, the sample mass returned will be restricted, highlighting the importance of developing instruments that can select the most promising samples for MSR. Raman spectroscopy is one favored technique for this purpose. Three Raman instruments will be sent onboard two upcoming Mars rover missions for the first time. In chapters 3-4, I investigated the challenges of Raman to identify samples for MSR. I examined two Raman systems, each optimized in a different way to mitigate a major problem commonly suffered by Raman instruments: background fluorescence. In Chapter 3, I focused on visible laser excitation wavelength (532 nm) gated (or time-resolved Raman, TRR) spectroscopy. Results showed occasional improvement over conventional Raman for mitigating fluorescence in samples. It was hypothesized that results were wavelength-dependent and that greater fluorescence reduction was possible with UV laser excitation. In Chapter 4, I tested this hypothesis with a time-resolved UV (266 nm) gated Raman and UV fluorescence spectroscopy capability. I acquired Raman and fluorescence data sets on samples and showed that the UV system enabled identifications of minerals and biosignatures in samples with high confidence. The results obtained in this dissertation may inform approaches for MSR by: (1) refining models for biosignature preservation in habitable Mars environments; (2) improving sample selection and caching strategies, which may increase the success of Earth-based biogenicity studies; and (3) informing the development of Raman instruments for upcoming rover-based missions.
(MSR) mission, Mars 2020, will be NASA's next step towards this goal, carrying an instrument suite that can identify samples containing potential biosignatures. Those samples will be later returned to Earth for detailed analysis. This dissertation is intended to inform strategies for fossil biosignature detection in Mars analog samples targeted for their high biosignature preservation potential (BPP) using in situ rover-based instruments. In chapter 2, I assessed the diagenesis and BPP of one relevant analog habitable Martian environment: a playa evaporite sequence within the Verde Formation, Arizona. Coupling outcrop-scale observations with laboratory analyses, results revealed four diagenetic pathways, each with distinct impacts on BPP. When MSR occurs, the sample mass returned will be restricted, highlighting the importance of developing instruments that can select the most promising samples for MSR. Raman spectroscopy is one favored technique for this purpose. Three Raman instruments will be sent onboard two upcoming Mars rover missions for the first time. In chapters 3-4, I investigated the challenges of Raman to identify samples for MSR. I examined two Raman systems, each optimized in a different way to mitigate a major problem commonly suffered by Raman instruments: background fluorescence. In Chapter 3, I focused on visible laser excitation wavelength (532 nm) gated (or time-resolved Raman, TRR) spectroscopy. Results showed occasional improvement over conventional Raman for mitigating fluorescence in samples. It was hypothesized that results were wavelength-dependent and that greater fluorescence reduction was possible with UV laser excitation. In Chapter 4, I tested this hypothesis with a time-resolved UV (266 nm) gated Raman and UV fluorescence spectroscopy capability. I acquired Raman and fluorescence data sets on samples and showed that the UV system enabled identifications of minerals and biosignatures in samples with high confidence. The results obtained in this dissertation may inform approaches for MSR by: (1) refining models for biosignature preservation in habitable Mars environments; (2) improving sample selection and caching strategies, which may increase the success of Earth-based biogenicity studies; and (3) informing the development of Raman instruments for upcoming rover-based missions.
ContributorsShkolyar, Svetlana (Author) / Farmer, Jack (Thesis advisor) / Semken, Steven (Committee member) / Sharp, Thomas (Committee member) / Shim, Sang-Heon Dan (Committee member) / Youngbull, Aaron Cody (Committee member) / Arizona State University (Publisher)
Created2016
Description
Amazonia, inhabited and investigated for millennia, continues to astonish scientists with its cultural and natural diversity. Although Amazonia is rapidly changing, its vast and varied landscape still contains a complex natural pharmacopeia. The Amazonian tribes have accrued valuable environmental and geological knowledge that can be studied. This dissertation demonstrates that Indigenous Knowledge considered alongside Western Science can enhance our understanding of the relationship of people to geological materials and hydrological resources, and reveal mineral medicines with practical applications.
I used methods from anthropology and geology to explore the geological knowledge of the Uitoto, a tribe of the Colombian Amazon. The Uitoto use two metaphors to describe Earth systems: 1. the earth is a body, and 2. the Amazon is a tree. I found that they classify surface-water systems according to observable characteristics and use mineral clays to treat various maladies. I argue that Uitoto knowledge about Amazonian mineral resources and surface water is practical, empirically–based and, in many cases, more nuanced than mainstream scientific knowledge.
I studied the mode of action of a natural antibacterial clay from the Colombian Amazon (AMZ) to discover whether the Uitoto’s claims about the clay’s medicinal values was verifiable using the methods of Western Science. Natural antibacterial clays can inhibit the growth of human pathogens. Methods from microbiology and geochemistry were combined to evaluate the mineral-microbe interactions that inhibit growth of model Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacteria. The AMZ antibacterial clay contains 45 % kaolinites and 30 % smectites. Its high surface area maintains an acidic environment (pH 4.5) and releases high concentrations of aluminum. Aluminum accumulates in the outer membrane of E. coli by binding to phospholipids. Furthermore, the membrane’s permeability increases due to synergistic effects between aluminum and transition metals released from the AMZ (i.e. Fe, Cu). The changes in the membrane may compromise its function as a barrier. Understanding the antibacterial mechanism of AMZ is key for its safe use as a natural product. These findings can help us harness the capabilities of antibacterial clays more efficiently.
Lastly, I integrated the results of this work in place-based, cross-cultural educational materials tailored for the tribal schools in the Colombian Amazon. The design of the units was informed by principles of curriculum design and successful pedagogic approaches for Native American students. The purpose of these educational materials is to return the results of research, enhance learning and participation of indigenous peoples in geosciences, and respond to the multicultural and plurilingual educational needs in countries such as Colombia.
I used methods from anthropology and geology to explore the geological knowledge of the Uitoto, a tribe of the Colombian Amazon. The Uitoto use two metaphors to describe Earth systems: 1. the earth is a body, and 2. the Amazon is a tree. I found that they classify surface-water systems according to observable characteristics and use mineral clays to treat various maladies. I argue that Uitoto knowledge about Amazonian mineral resources and surface water is practical, empirically–based and, in many cases, more nuanced than mainstream scientific knowledge.
I studied the mode of action of a natural antibacterial clay from the Colombian Amazon (AMZ) to discover whether the Uitoto’s claims about the clay’s medicinal values was verifiable using the methods of Western Science. Natural antibacterial clays can inhibit the growth of human pathogens. Methods from microbiology and geochemistry were combined to evaluate the mineral-microbe interactions that inhibit growth of model Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacteria. The AMZ antibacterial clay contains 45 % kaolinites and 30 % smectites. Its high surface area maintains an acidic environment (pH 4.5) and releases high concentrations of aluminum. Aluminum accumulates in the outer membrane of E. coli by binding to phospholipids. Furthermore, the membrane’s permeability increases due to synergistic effects between aluminum and transition metals released from the AMZ (i.e. Fe, Cu). The changes in the membrane may compromise its function as a barrier. Understanding the antibacterial mechanism of AMZ is key for its safe use as a natural product. These findings can help us harness the capabilities of antibacterial clays more efficiently.
Lastly, I integrated the results of this work in place-based, cross-cultural educational materials tailored for the tribal schools in the Colombian Amazon. The design of the units was informed by principles of curriculum design and successful pedagogic approaches for Native American students. The purpose of these educational materials is to return the results of research, enhance learning and participation of indigenous peoples in geosciences, and respond to the multicultural and plurilingual educational needs in countries such as Colombia.
ContributorsLondoño Arias, Sandra Carolina (Author) / Williams, Lynda B (Thesis advisor) / Semken, Steven (Thesis advisor) / Brandt, Elizabeth A. (Committee member) / Hartnett, Hilairy H (Committee member) / Raymond, Jason (Committee member) / Arizona State University (Publisher)
Created2016
Description
This dissertation is presented in two sections. First, I explore two methods of using stable isotope analysis to trace environmental and biogeochemical processes. Second, I present two related studies investigating student understanding of the biogeochemical concepts that underlie part one. Fe and Hg are each biogeochemically important elements in their own way. Fe is a critical nutrient for phytoplankton, while Hg is detrimental to nearly all forms of life. Fe is often a limiting factor in marine phytoplankton growth. The largest source, by mass, of Fe to the open ocean is windblown mineral dust, but other more soluble sources are more bioavailable. To look for evidence of these non-soil dust sources of Fe to the open ocean, I measured the isotopic composition of aerosol samples collected on Bermuda. I found clear evidence in the fine size fraction of a non-soil dust Fe source, which I conclude is most likely from biomass burning. Widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Isotope analysis would be a useful tool in quantifying this impact if the isotopic composition of Hg from CFL were known. My measurements show that CFL-Hg is isotopically fractionated, in a unique pattern, during normal operation. This fractionation is large and has a distinctive, mass-independent signature, such that CFL Hg can be uniquely identified from other sources. Misconceptions research in geology has been a very active area of research, but student thinking regarding the related field of biogeochemistry has not yet been studied in detail. From interviews with 40 undergraduates, I identified over 150 specific misconceptions. I also designed a multiple-choice survey (concept inventory) to measure understanding of these same biogeochemistry concepts. I present statistical evidence, based on the Rasch model, for the reliability and validity of this instrument. This instrument will allow teachers and researchers to easily quantify learning outcomes in biogeochemistry and will complement existing concept inventories in geology, chemistry, and biology.
ContributorsMead, Chris (Author) / Anbar, Ariel (Thesis advisor) / Semken, Steven (Committee member) / Shock, Everett (Committee member) / Herckes, Pierre (Committee member) / Hartnett, Hilairy (Committee member) / Arizona State University (Publisher)
Created2014
Description
Earth's topographic surface forms an interface across which the geodynamic and geomorphic engines interact. This interaction is best observed along crustal margins where topography is created by active faulting and sculpted by geomorphic processes. Crustal deformation manifests as earthquakes at centennial to millennial timescales. Given that nearly half of Earth's human population lives along active fault zones, a quantitative understanding of the mechanics of earthquakes and faulting is necessary to build accurate earthquake forecasts. My research relies on the quantitative documentation of the geomorphic expression of large earthquakes and the physical processes that control their spatiotemporal distributions. The first part of my research uses high-resolution topographic lidar data to quantitatively document the geomorphic expression of historic and prehistoric large earthquakes. Lidar data allow for enhanced visualization and reconstruction of structures and stratigraphy exposed by paleoseismic trenches. Lidar surveys of fault scarps formed by the 1992 Landers earthquake document the centimeter-scale erosional landforms developed by repeated winter storm-driven erosion. The second part of my research employs a quasi-static numerical earthquake simulator to explore the effects of fault roughness, friction, and structural complexities on earthquake-generated deformation. My experiments show that fault roughness plays a critical role in determining fault-to-fault rupture jumping probabilities. These results corroborate the accepted 3-5 km rupture jumping distance for smooth faults. However, my simulations show that the rupture jumping threshold distance is highly variable for rough faults due to heterogeneous elastic strain energies. Furthermore, fault roughness controls spatiotemporal variations in slip rates such that rough faults exhibit lower slip rates relative to their smooth counterparts. The central implication of these results lies in guiding the interpretation of paleoseismically derived slip rates that are used to form earthquake forecasts. The final part of my research evaluates a set of Earth science-themed lesson plans that I designed for elementary-level learning-disabled students. My findings show that a combination of concept delivery techniques is most effective for learning-disabled students and should incorporate interactive slide presentations, tactile manipulatives, teacher-assisted concept sketches, and student-led teaching to help learning-disabled students grasp Earth science concepts.
ContributorsHaddad, David Elias (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen (Committee member) / Semken, Steven (Committee member) / Shirzaei, Manoochehr (Committee member) / Whipple, Kelin (Committee member) / Zielke, Olaf (Committee member) / Arizona State University (Publisher)
Created2014
Description
ABSTRACT
The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic centers on Mars, such as those seen the southern flank of Pavonis Mons and in the Tempe Terra region of Mars. The eruptive history of the volcanic field is established through detailed geologic map supplemented by geochemical, paleomagnetic, and geochronological analysis.
Paleomagnetic analyses were completed on 473 oriented core samples from 58 sites. Mean inclination and declination directions were calculated from 8-12 samples at each site. Fifty sites revealed well-grouped natural remanent magnetization vectors after applying alternating field demagnetization. Thirty-nine sites had reversed polarity, eleven had normal polarity. Fifteen unique paleosecular variation inclination and declination directions were identified, six were represented by more than one site with resultant vectors that correlated within a 95% confidence interval. Four reversed sites were radiometrically dated to the Matuyama Chron with ages ranging from 1.08 ± 0.15 Ma to 2.37 ± 0.02 Ma; and one normal polarity site was dated to the Olduvai normal excursion at 1.91 ± 0.59 Ma. Paleomagnetic correlations within a 95% confidence interval were used to extrapolate radiogenic dates. Results reveal 3-5 eruptive stages over ~1.5 Ma in the early Pleistocene and that the SAVF dammed and possibly diverted the lower Gila River multiple times. Preliminary modeling of the median clast size of the terrace deposits suggests a maximum discharge of ~11300 cms (~400,000 cfs) was necessary to transport observed sediment load, which is larger than the historically recorded discharge of the modern Gila River.
The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic centers on Mars, such as those seen the southern flank of Pavonis Mons and in the Tempe Terra region of Mars. The eruptive history of the volcanic field is established through detailed geologic map supplemented by geochemical, paleomagnetic, and geochronological analysis.
Paleomagnetic analyses were completed on 473 oriented core samples from 58 sites. Mean inclination and declination directions were calculated from 8-12 samples at each site. Fifty sites revealed well-grouped natural remanent magnetization vectors after applying alternating field demagnetization. Thirty-nine sites had reversed polarity, eleven had normal polarity. Fifteen unique paleosecular variation inclination and declination directions were identified, six were represented by more than one site with resultant vectors that correlated within a 95% confidence interval. Four reversed sites were radiometrically dated to the Matuyama Chron with ages ranging from 1.08 ± 0.15 Ma to 2.37 ± 0.02 Ma; and one normal polarity site was dated to the Olduvai normal excursion at 1.91 ± 0.59 Ma. Paleomagnetic correlations within a 95% confidence interval were used to extrapolate radiogenic dates. Results reveal 3-5 eruptive stages over ~1.5 Ma in the early Pleistocene and that the SAVF dammed and possibly diverted the lower Gila River multiple times. Preliminary modeling of the median clast size of the terrace deposits suggests a maximum discharge of ~11300 cms (~400,000 cfs) was necessary to transport observed sediment load, which is larger than the historically recorded discharge of the modern Gila River.
ContributorsCave, Shelby Renee (Author) / Clarke, Amanda (Thesis advisor) / Burt, Donald (Committee member) / Reynolds, Stephen (Committee member) / Semken, Steven (Committee member) / Schmeeckle, Mark (Committee member) / Arizona State University (Publisher)
Created2015
Description
This is a qualitative study about sources of self-efficacy and roles of assistive technologies (AT) associated with the science, technology, engineering and mathematics (STEM) choice and participation of STEM professionals and graduate students with sensory and orthopedic disabilities. People with disabilities are underrepresented in STEM, which can be traced back along the STEM pipeline to early undergraduate participation in STEM. Little research exists, however, about pathways and factors associated with successful STEM participation for people with disabilities at any point along their trajectories. Eighteen STEM professionals and graduate students with sensory and orthopedic disabilities were interviewed for this study. Sources of self-efficacy were sought from interview transcripts, as were emergent themes associated with the types, uses and roles of AT. Findings suggest that people with sensory and orthopedic disabilities weigh sources of self-efficacy differently from white males without disabilities in STEM and more like other underrepresented minorities in STEM. Social persuasions were most frequently reported and in far more detail than other sources, suggesting that this source may be most impactful in the development of self-efficacy beliefs for this group. Additionally, findings indicate that AT is critical to the successful participation of people with sensory and orthopedic disabilities in STEM at all points along their STEM pathways. Barriers center around issues of access to full engagement in mainstream STEM classrooms and out of school opportunities as well as the impact of ill-informed perceptions about the capabilities of people with disabilities held by parents, teachers and college faculty who can act as gatekeepers along STEM pathways. Gaps in disability specialists' knowledge about STEM-specific assistive technologies, especially at the college level, are also problematic. The prevalence of mainstream public school attendance reported by participants indicates that classroom teachers and disability-related educators have important roles in providing access to STEM mastery experiences as well as providing positive support and high expectations for students with disabilities. STEM and disability-based networks served to provide participants with role models, out of school STEM learning experiences and important long-term social connections in STEM communities.
ContributorsPacheco, Heather A (Author) / Baker, Dale R. (Thesis advisor) / Forouzesh, Mohammed (Committee member) / Pavri, Shireen (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2014
Description
For this dissertation, three separate papers explore the study areas of the western Grand Canyon, the Grand Staircase (as related to Grand Canyon) and Desolation Canyon on the Green River in Utah.
In western Grand Canyon, I use comparative geomorphology between the Grand Canyon and the Grand Wash Cliffs (GWC). We propose the onset of erosion of the GWC is caused by slip on the Grand Wash Fault that formed between 18 and 12 million years ago. Hillslope angle and channel steepness are higher in Grand Canyon than along the Grand Wash Cliffs despite similar rock types, climate and base level fall magnitude. These experimental controls allow inference that the Grand Canyon is younger and eroding at a faster rate than the Grand Wash Cliffs.
The Grand Staircase is the headwaters of some of the streams that flow into Grand Canyon. A space-for-time substitution of erosion rates, supported by landscape simulations, implies that the Grand Canyon is the result of an increase in base level fall rate, with the older, slower base level fall rate preserved in the Grand Staircase. Our data and analyses also support a younger, ~6-million-year estimate of the age of Grand Canyon that is likely related to the integration of the Colorado River from the Colorado Plateau to the Basin and Range. Complicated cliff-band erosion and its effect on cosmogenic erosion rates are also explored, guiding interpretation of isotopic data in landscapes with stratigraphic variation in quartz and rock strength.
Several hypotheses for the erosion of Desolation Canyon are tested and refuted, leaving one plausible conclusion. I infer that the Uinta Basin north of Desolation Canyon is eroding slowly and that its form represents a slow, stable base level fall rate. Downstream of Desolation Canyon, the Colorado River is inferred to have established itself in the exhumed region of Canyonlands and to have incised to near modern depths prior to the integration of the Green River and the production of relief in Desolation Canyon. Analysis of incision and erosion rates in the region suggests integration is relatively recent.
In western Grand Canyon, I use comparative geomorphology between the Grand Canyon and the Grand Wash Cliffs (GWC). We propose the onset of erosion of the GWC is caused by slip on the Grand Wash Fault that formed between 18 and 12 million years ago. Hillslope angle and channel steepness are higher in Grand Canyon than along the Grand Wash Cliffs despite similar rock types, climate and base level fall magnitude. These experimental controls allow inference that the Grand Canyon is younger and eroding at a faster rate than the Grand Wash Cliffs.
The Grand Staircase is the headwaters of some of the streams that flow into Grand Canyon. A space-for-time substitution of erosion rates, supported by landscape simulations, implies that the Grand Canyon is the result of an increase in base level fall rate, with the older, slower base level fall rate preserved in the Grand Staircase. Our data and analyses also support a younger, ~6-million-year estimate of the age of Grand Canyon that is likely related to the integration of the Colorado River from the Colorado Plateau to the Basin and Range. Complicated cliff-band erosion and its effect on cosmogenic erosion rates are also explored, guiding interpretation of isotopic data in landscapes with stratigraphic variation in quartz and rock strength.
Several hypotheses for the erosion of Desolation Canyon are tested and refuted, leaving one plausible conclusion. I infer that the Uinta Basin north of Desolation Canyon is eroding slowly and that its form represents a slow, stable base level fall rate. Downstream of Desolation Canyon, the Colorado River is inferred to have established itself in the exhumed region of Canyonlands and to have incised to near modern depths prior to the integration of the Green River and the production of relief in Desolation Canyon. Analysis of incision and erosion rates in the region suggests integration is relatively recent.
ContributorsDarling, Andrew Lee (Author) / Whipple, Kelin (Thesis advisor) / Semken, Steven (Committee member) / Arrowsmith, Ramon (Committee member) / DeVecchio, Duane (Committee member) / Heimsath, Arjun (Committee member) / Arizona State University (Publisher)
Created2016