Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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Description
An array of north-striking, left-stepping, active normal faults is situated along the southwestern margin of the Gulf of California. This normal fault system is the marginal fault system of the oblique-divergent plate boundary within the Gulf of California. To better understand the role of upper-crustal processes during development of an obliquely rifted plate margin, gravity surveys were conducted across the normal-fault-bounded basins within the gulf-margin array and, along with optically stimulated luminescence dating of offset surfaces, fault-slip rates were estimated and fault patterns across basins were assessed, providing insight into sedimentary basin evolution. Additionally, detailed geologic and geomorphic maps were constructed along two faults within the system, leading to a more complete understanding of the role of individual normal faults within a larger array. These faults slip at a low rate (0.1-1 mm/yr) and have relatively shallow hanging wall basins (~500-3000 m). Overall, the gulf-margin faults accommodate protracted, distributed deformation at a low rate and provide a minor contribution to overall rifting. Integrating figures with text can lead to greater science learning than when either medium is presented alone. Textbooks, composed of text and graphics, are a primary source of content in most geology classes. It is essential to understand how students approach learning from text and figures in textbook-style learning materials and how the arrangement of the text and figures influences their learning approach. Introductory geology students were eye tracked while learning from textbook-style materials composed of text and graphics. Eye fixation data showed that students spent less time examining the figure than the text, but the students who more frequently examined the figure tended to improve more from the pretest to the posttest. In general, students tended to examine the figure at natural breaks in the reading. Textbook-style materials should, therefore, be formatted to include a number of natural breaks so that learners can pause to inspect the figure without the risk of losing their place in the reading and to provide a chance to process the material in small chunks. Multimedia instructional materials should be designed to support the cognitive processes of the learner.
ContributorsBusch, Melanie M. D (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen (Thesis advisor) / Chi, Michelene (Committee member) / Semken, Steven (Committee member) / Tyburczy, James (Committee member) / Arizona State University (Publisher)
Created2011
Description
Chemical and mineralogical data from Mars shows that the surface has been chemically weathered on local to regional scales. Chemical trends and the types of chemical weathering products present on the surface and their abundances can elucidate information about past aqueous processes. Thermal-infrared (TIR) data and their respective models are essential for interpreting Martian mineralogy and geologic history. However, previous studies have shown that chemical weathering and the precipitation of fine-grained secondary silicates can adversely affect the accuracy of TIR spectral models. Furthermore, spectral libraries used to identify minerals on the Martian surface lack some important weathering products, including poorly-crystalline aluminosilicates like allophane, thus eliminating their identification in TIR spectral models. It is essential to accurately interpret TIR spectral data from chemically weathered surfaces to understand the evolution of aqueous processes on Mars. Laboratory experiments were performed to improve interpretations of TIR data from weathered surfaces. To test the accuracy of deriving chemistry of weathered rocks from TIR spectroscopy, chemistry was derived from TIR models of weathered basalts from Baynton, Australia and compared to actual weathering rind chemistry. To determine how specific secondary silicates affect the TIR spectroscopy of weathered basalts, mixtures of basaltic minerals and small amounts of secondary silicates were modeled. Poorly-crystalline aluminosilicates were synthesized and their TIR spectra were added to spectral libraries. Regional Thermal Emission Spectrometer (TES) data were modeled using libraries containing these poorly-crystalline aluminosilicates to test for their presence on the Mars. Chemistry derived from models of weathered Baynton basalts is not accurate, but broad chemical weathering trends can be interpreted from the data. TIR models of mineral mixtures show that small amounts of crystalline and amorphous silicate weathering products (2.5-5 wt.%) can be detected in TIR models and can adversely affect modeled plagioclase abundances. Poorly-crystalline aluminosilicates are identified in Northern Acidalia, Solis Planum, and Meridiani. Previous studies have suggested that acid sulfate weathering was the dominant surface alteration process for the past 3.5 billion years; however, the identification of allophane indicates that alteration at near-neutral pH occurred on regional scales and that acid sulfate weathering is not the only weathering process on Mars.
ContributorsRampe, Elizabeth Barger (Author) / Sharp, Thomas G (Thesis advisor) / Christensen, Phillip (Committee member) / Hervig, Richard (Committee member) / Shock, Everett (Committee member) / Williams, Lynda (Committee member) / Arizona State University (Publisher)
Created2011
Description
A new analytical method is proposed for measuring the deuterium to hydrogen ratio (D/H) of non-stoichiometric water in hydrous minerals via pyrolysis facilitated gas-chromatography - isotope ratio mass spectrometry (GC-IRMS). Previously published analytical methods have reported a poorly understood nonlinear dependence of D/H on sample size, for which any accurate correction is difficult. This sample size effect been variously attributed to kinetic isotope fractionation within the mass spectrometer and peripheral instruments, ion source linearity issues, and an unstable H_3^+-factor or incorrect H_3^+-factor calculations. The cause of the sample size effect is here identified by examinations of individual chromatograms as well as bulk data from chromatographic peaks. It is here determined that it is primarily an artifact of the calculations employed by the manufacturer's computer program, used to both monitor the functions of the mass spectrometer and to collect data. Ancillary causes of the sample size effect include a combination of persistent background interferences and chromatographic separation of the isotopologues of molecular hydrogen. Previously published methods are evaluated in light of these findings. A new method of H_3^+-factor and D/H calculation is proposed which makes portions of the Isodat software as well as other published calculation methods unnecessary. Using this new method, D/H is measured in non-stoichiometric water in chert from the Cretaceous Edwards Group, Texas, as well as the Precambrian Kromberg Formation, South Africa, to assess hydrological conditions as well as to estimate the maximum average surface temperature during precipitation of the chert. Data from Cretaceous chert are consistent with previously published data and interpretations, based upon conventional analyses of large samples. Data from Precambrian chert are consistent with maximum average surface temperatures approaching 65°C during the Archean, instead of the much lower temperatures derived from erroneous methods of sample preparation and analysis. D/H is likewise measured in non-stoichiometric water in silicified basalt from the Precambrian Hooggenoeg Complex, South Africa. Data are shown to be consistent with D/H of the Archean ocean similar to present day values.
ContributorsSheehan, Michael Robert (Author) / Knauth, Leroy P (Thesis advisor) / Anbar, Ariel (Committee member) / Farmer, Jack (Committee member) / Arizona State University (Publisher)
Created2011
Description
Dust devils have proven to be commonplace on Mars, although their occurrence is unevenly distributed across the surface. They were imaged or inferred by all six successful landed spacecraft: the Viking 1 and 2 Landers (VL-1 and VL-2), Mars Pathfinder Lander, the Mars Exploration Rovers Spirit and Opportunity, and the Phoenix Mars Lander. Comparisons of dust devil parameters were based on results from optical and meteorological (MET) detection campaigns. Spatial variations were determined based on comparisons of their frequency, morphology, and behavior. The Spirit data spanning three consecutive martian years is used as the basis of comparison because it is the most extensive on this topic. Average diameters were between 8 and 115 m for all observed or detected dust devils. The average horizontal speed for all of the studies was roughly 5 m/s. At each site dust devil densities peaked between 09:00 and 17:00 LTST during the spring and summer seasons supporting insolation-driven convection as the primary formation mechanism. Seasonal number frequency averaged ~1 dust devils/ km2/sol and spanned a total of three orders of magnitude. Extrapolated number frequencies determined for optical campaigns at the Pathfinder and Spirit sites accounted for temporal and spatial inconsistencies and averaged ~19 dust devils/km2/sol. Dust fluxes calculated from Pathfinder data (5x10-4 kg/m2/s and 7x10-5 kg/m2/s) were well with in the ranges calculated from Spirit data (4.0x10-9 to 4.6x10-4 kg/m2/s for Season One, 5.2x10-7 to 6.2x10-5 kg/m2/s during Season Two, and 1.5x10-7 to 1.6x10-4 kg/m2/s during Season Three). Based on the results a campaign is written for improvements in dust devil detection at the Mars Science Laboratory's (MSL) site. Of the four remaining candidate MSL sites, the dusty plains of Gale crater may potentially be the site with the highest probability of dust devil activity.
ContributorsWaller, Devin (Author) / Greeley, Ronald (Thesis advisor) / Christensen, Philip R. (Philip Russel) (Committee member) / Cerveny, Randall (Committee member) / Arizona State University (Publisher)
Created2011
Description
The Santa Gertrudis Mining District of Sonora, Mexico contains more than a dozen purported Carlin-like, sedimentary-hosted, disseminated-gold deposits. A series of near-surface, mostly oxidized gold deposits were open-pit mined from the calcareous and clastic units of the Cretaceous Bisbee Group. Gold occurs as finely disseminated, sub-micron coatings on sulfides, associated with argillization and silicification of calcareous, carbonaceous, and siliciclastic sedimentary rocks in structural settings. Gold occurs with elevated levels of As, Hg, Sb, Pb, and Zn. Downhole drill data within distal disseminated gold zones reveal a 5:1 ratio of Ag:Au and strong correlations of Au to Pb and Zn. This study explores the timing and structural control of mineralization utilizing field mapping, geochemical studies, drilling, core logging, and structural analysis. Most field evidence indicates that mineralization is related to a single pulse of moderately differentiated, Eocene intrusives described as Mo-Cu-Au skarn with structurally controlled distal disseminated As-Ag-Au.
ContributorsGeier, John Jeffrey (Author) / Reynolds, Stephen J. (Thesis advisor) / Burt, Donald (Committee member) / Stump, Edmund (Committee member) / Arizona State University (Publisher)
Created2011
Description
The Byrd Glacier region of Antarctica is important for understanding the tectonic development and landscape evolution of the Transantarctic Mountains (TAM). This outlet glacier crossing the TAM marks a major discontinuity in the Neoproterozoic-early Paleozoic Ross orogen. The region has not been geologically mapped in detail, but previous studies have inferred a fault to exist beneath and parallel to the direction of flow of Byrd Glacier. Thermochronologic analysis has never been undertaken across Byrd Glacier, and little is known of the exhumation history of the region. The objectives of this study are to assess possible differential movement across the inferred Byrd Glacier fault, to measure the timing of exhumation, and to gain a better overall understanding of the structural architecture of the TAM. Apatites and zircons separated from rock samples collected from various locations north and south of Byrd Glacier were dated using single-crystal (U- Th)/He analysis. Similar cooling histories were revealed with comparable exhumation rates of 0.03 ± 0.003 and 0.04 ± 0.03 mm/yr north and south of Byrd Glacier from apatite data and somewhat similar rates of 0.06 ± 0.008 and 0.04 ± 0.01 mm/yr north and south of Byrd Glacier from zircon data. Age vs. elevation regressions indicate a vertical offset of 1379 ± 159 m and 4000 ± 3466 m from apatite and zircon data. To assess differential movement, the Kukri Peneplain (a regional unconformity) was utilized as a datum. On-site photographs, Landsat imagery, and Aster Global DEM data were combined to map Kukri Peneplain elevation points north and south of Byrd Glacier. The difference in elevation of the peneplain as projected across Byrd Glacier shows an offset of 1122 ± 4.7 m. This study suggests a model of relatively uniform exhumation followed by fault displacement that uplifted the south side of Byrd Glacier relative to the north side. Combining apatite and zircon (U-Th)/He analysis along with remote geomorphologic analysis has provided an understanding of the differential movement and exhumation history of crustal blocks in the Byrd Glacier region. The results complement thermochronologic and geomorphologic studies elsewhere within the TAM providing more information and a new approach.
ContributorsFoley, Daniel Joseph (Author) / Stump, Edmund (Thesis advisor) / Whipple, Kelin X (Committee member) / Hodges, Kip (Committee member) / Arizona State University (Publisher)
Created2011
Description
The San Andreas Fault (SAF) is the primary structure within a system of faults accommodating motion between the North American and Pacific plates. Physical models of faulting and characterizations of seismic hazard are informed by investigations of paleoseismology, slip distribution, and slip rate. The impact of earthquakes on people is due in large part to social vulnerability. This dissertation contributes an analysis about the relationships between earthquake hazard and social vulnerability in Los Angeles, CA and investigations of paleoseismology and fault scarp array complexity on the central SAF. Analysis of fault scarp array geometry and morphology using 0.5 m digital elevation models along 122 km of the central SAF reveals significant variation in the complexity of SAF structure. Scarp trace complexity is measured by scarp separation, changes in strike, fault trace gaps, and scarp length per SAF kilometer. Geometrical complexity in fault scarp arrays indicates that the central SAF can be grouped into seven segments. Segment boundaries are controlled by interactions with subsidiary faults. Investigation of an offset channel at Parkfield, CA yields a late Holocene slip rate of 26.2 +6.4/- 4.3 mm/yr. This rate is lower than geologic measurements on the Carrizo section of the SAF and rates implied by far-field geodesy. However, it is consistent with historical observations of slip at Parkfield. Paleoseismology at Parkfield indicates that large earthquakes are absent from the stratigraphic record for at least a millennia. Together these observations imply that the amount of plate boundary slip accommodated by the main SAF varies along strike. Contrary to most environmental justice analyses showing that vulnerable populations are spatially-tied to environmental hazards, geospatial analyses relating social vulnerability and earthquake hazard in southern California show that these groups are not disproportionately exposed to the areas of greatest hazard. Instead, park and green space is linked to earthquake hazard through fault zone regulation. In Los Angeles, a parks poor city, the distribution of social vulnerability is strongly tied to a lack of park space. Thus, people with access to financial and political resources strive to live in neighborhoods with parks, even in the face of forewarned risk.
ContributorsToké, Nathan A (Author) / Arrowsmith, J R (Thesis advisor) / Boone, Christopher G (Committee member) / Heimsath, Arjun M (Committee member) / Shock, Everett L (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2011
Description
Meter-resolution topography gathered by LiDAR (Light Detection and Ranging) has become an indispensable tool for better understanding of many surface processes including those sculpting landscapes that record information about earthquake hazards for example. For this reason, and because of the spectacular representation of the phenomena that these data provide, it is appropriate to integrate these data into Earth science educational materials. I seek to answer the following research question: "will using the LiDAR topography data instead of, or alongside, traditional visualizations and teaching methods enhance a student's ability to understand geologic concepts such as plate tectonics, the earthquake cycle, strike-slip faults, and geomorphology?" In order to answer this question, a ten-minute introductory video on LiDAR and its uses for the study of earthquakes entitled "LiDAR: Illuminating Earthquake Hazards" was produced. Additionally, LiDAR topography was integrated into the development of an undergraduate-level educational activity, the San Andreas fault (SAF) earthquake cycle activity, designed to teach introductory Earth science students about the earthquake cycle. Both the LiDAR video and the SAF activity were tested in undergraduate classrooms in order to determine their effectiveness. A pretest and posttest were administered to introductory geology lab students. The results of these tests show a notable increase in understanding LiDAR topography and its uses for studying earthquakes from pretest to posttest after watching the video on LiDAR, and a notable increase in understanding the earthquake cycle from pretest to posttest using the San Andreas Fault earthquake cycle exercise. These results suggest that the use of LiDAR topography within these educational tools is beneficial for students when learning about the earthquake cycle and earthquake hazards.
ContributorsRobinson, Sarah Elizabeth (Author) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2011
Description
The spectacular geological panoramas of Grand Canyon National Park (GCNP) motivate the curiosity of visitors about geology. However, there is little research on how well these visitors understand the basic geologic principles on display in the Canyon walls. The new Trail of Time (ToT) interpretative exhibit along the South Rim uses Grand Canyon vistas to teach these principles. Now being visited by thousands daily, the ToT is a uniquely valuable setting for research on informal learning of geologic time and other basic geologic concepts. At the ToT, visitors are not only asked to comprehend a linear timeline, but to associate it with the strata exposed in the walls of the Canyon. The research addressed two primary questions: (1) how do visitors of the National Park use elements of the geologic landscape of the Grand Canyon to explain fundamental principles of relative geologic time? and (2) how do visitors reconcile the relationship between the horizontal ToT timeline and the vertical encoding of time in the strata exposed in the Canyon walls? Semi-structured interviews tracked participants' understanding of the ToT exhibit and of basic principles of geologic time. Administering the verbal analysis method of Chi (1997) to the interview transcripts, the researcher identified emergent themes related to how the respondents utilized the landscape to answer interview questions. Results indicate that a majority of respondents are able to understand principles of relative geologic time by utilizing both the observed and inferred landscape of Grand Canyon. Results also show that by applying the same integrated approach to the landscape, a majority of respondents are able to reconcile stratigraphic time with the horizontal ToT timeline. To gain deeper insight into the cognitive skills activated to correctly understand geologic principles the researcher used Dodick and Orion's application of Montangero's (1996) diachronic thinking model to code responses into three schemes: (1) transformation, (2) temporal organization, and (3) interstage linkage. Results show that correct responses required activation of the temporal organization scheme or the more advanced interstage linkage scheme. Appropriate application of these results can help inform the development of future outdoor interpretive geoscience exhibits.
ContributorsFrus, Rebecca (Author) / Semken, Steven (Thesis advisor) / Baker, Dale (Committee member) / Farmer, Jack (Committee member) / Arizona State University (Publisher)
Created2011
Description
The goal of this study is to gain a better understanding of earthquake distribution and regional tectonic structure across Arizona. To achieve this objective, I utilized seismic data from EarthScope's USArray Transportable Array (TA), which was deployed in Arizona from April 2006 to March 2009. With station spacing of approximately 70 km and ~3 years of continuous three-component broadband seismic data, the TA provided an unprecedented opportunity to develop the first seismicity catalog for Arizona without spatial sampling bias. In this study I developed a new data analysis workflow to detect smaller scale seismicity across a regional study area, which serves as a template for future regional analyses of TA data and similar datasets. The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity.
ContributorsLockridge, Jeffrey Steven (Author) / Fouch, Matthew J (Thesis advisor) / Arrowsmith, Ramon (Thesis advisor) / Reynolds, Stephen J. (Committee member) / Arizona State University (Publisher)
Created2011