Matching Items (6)
Filtering by
- Creators: School of Earth and Space Exploration
Description
There are many outstanding questions regarding the petrologic processes that give rise to andesitic and basaltic magmas in subduction zones, including the specifics that govern their geographical distribution in a given arc segment. Here I investigate the genesis of calc-alkaline and tholeiitic basalts from the Lassen Volcanic Center in order to determine the pressure, temperature, source composition, and method of melting that lead to the production of melt in the mantle below Lassen. To this aim, a suite of primitive basalts (i.e. SiO2<52 and Mg#>65) are corrected for fractional crystallization by adding minerals back to the bulk rock composition with the goal of returning them to a primary composition in equilibrium with the mantle. Thermobarometry of the primary melt compositions is conducted to determine temperature and pressure of melting, in addition to a forward mantle modeling technique to simulate mantle melting at varying pressures to constrain source composition and method of melting (batch vs. fractional). The results from the two techniques agree on an average depth of melt extraction of 36 km and a source composition similar to that of depleted mantle melted by batch melting. Although attempted for both calc-alkaline and tholeiitic basalts, the fractional crystallization correction and thus the pressure-temperature calculations were only successful for tholeiitic basalts due to the hydrous nature of the calc-alkaline samples. This leaves an opportunity to repeat this study with parameters appropriate for hydrous basalts, allowing for the comparison of calc-alkaline and tholeiitic melting conditions.
ContributorsSheppard, Katherine Davis (Author) / Till, Christy (Thesis director) / Hervig, Richard (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2015-05
Description
This research focuses on a geologic controversy regarding the stratigraphic position of the Hermit Formation outside of the Grand Canyon, specifically in Sedona, Arizona. The goal of this research is to provide additional constraints on this dispute by pinpointing the transition to the Hermit Formation in Sedona, if possible. To accomplish this, we use field observations and detrital zircon dating techniques to compare data we collected in Sedona with data previously published for the Grand Canyon. Fossil evidence in Sedona and near Payson, Arizona is also used to aid correlation. Starting from the Grand Canyon, the Hermit Formation pinches out to the southeast and, hypothetically obstructed by the Sedona Arch, does not reach Sedona. Detrital zircon data show similar age distributions between the Grand Canyon and Sedona rock units, but the results are not strong enough to confidently correlate units between these two localities. The data collected for this study suggest that if the Hermit Formation is present in Sedona, it is limited to higher up in the section as opposed to occupying the middle portion of the section as is currently interpreted. To determine with greater accuracy whether the Hermit Formation does exist higher in the section of Sedona, more detrital zircons should be collected and analyzed from the part of the section that yielded a relative increase in young zircons aged 200-600 Ma.
ContributorsFinger, Mikayla (Co-author) / Spitzer, Patrick (Co-author) / Reynolds, Stephen (Thesis director) / Semken, Steven (Committee member) / DeVecchio, Duane (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The Star Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M dwarfs in the far-ultraviolet (FUV) and near-ultraviolet (NUV) (160 and 280 nm respectively), measuring the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. The delta-doped detectors baselined for SPARCS have demonstrated more than five times the in-band quantum efficiency of the detectors of GALEX. Given that red:UV photon emission from cool, low-mass stars can be million:one, UV observation of thes stars are susceptible to red light contamination. In addition to the high efficiency delta-doped detectors, SPARCS will include red-rejection filters to help minimize red leak. Even so, careful red-rejection and photometric calibration is needed. As was done for GALEX, white dwarfs are used for photometric calibration in the UV. We find that the use of white dwarfs to calibrate the observations of red stars leads to significant errors in the reported flux, due to the differences in white dwarf and red dwarf spectra. Here we discuss the planned SPARCS calibration model and the color correction, and demonstrate the importance of this correction when recording UV measurements of M stars taken by SPARCS.
ContributorsOsby, Ella (Author) / Shkolnik, Evgenya (Thesis director) / Ardila, David (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Gamma-ray bursts (GRBs) are a type of astrophysical transient resulting from the most energetic explosions known in the universe. The explosions occur in distant galaxies, and their bright initial emission may only last a few seconds. Colibri is a telescope being built at the San Pedro Martir Observatory in Baja, CA, MX with high sensitivity in order to study these events at a high redshift. Due to how quickly GRBs occur, it is essential to develop an image reduction pipeline that can quickly and accurately detect these events. Using existing image reduction software from Coatli, which was programmed and optimized for speed using python, numerous time trials were performed in order to determine if the pipeline meets the time requirements with various factors being adjusted. The goal of this experiment is for the telescope to respond to, capture, and reduce the images in under 3 minutes. It was determined that the reduction was optimized when the number of files to be reduced was set equal to 16 or higher by changing the batch number and the blank sky subtraction function was performed. As for the number of exposures, one can take up to four 30 second exposures or twenty 5 second exposures and reduce them in under 3 minutes.
ContributorsHeiligenstein, Wren (Author) / Butler, Nathaniel (Thesis director) / Jansen, Rolf (Committee member) / Dimitrova, Tzvetelina (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2024-05
Description
Cinder cones are common volcanic structures that occur in fields, and on the flanks of shield volcanoes, stratovolcanoes, and calderas. Because they are common structures, they have a significant possibility of impacting humans and human environments. As such, there is a need to analyze cinder cones to get a better understanding of their eruptions and associated hazards. I will approach this analysis by focusing on volcanic bombs and ballistics, which are large clots of lava that are launched from the volcanic vent, follow ballistic trajectories, and can travel meters to a few kilometers from their source (e.g. Fagents and Wilson 1993; Waitt et al. 1995).
Tecolote Volcano in the Pinacate Volcanic Field in Mexico contains multiple vents within a horseshoe-shaped crater that have all produced various ejecta (Zawacki et al. 2019). The objectives of this research are to map ballistic distribution to understand the relationship between the source vent or vents and the bombs and ballistics that litter the region around Tecolote, and interpret the eruption conditions that ejected those bombs by using their distributions, morphologies, and fine-scale textures.
The findings of this work are that these bombs are apparently from the last stages of the eruption, succeeding the final lava flows. The interiors and exteriors of the bombs display different cooling rates which can are indicated by the fabric found within. Using this, certain characteristics of the bombs during eruption were extrapolated. The ‘cow pie’ bombs were determined to be the least viscous or contained a higher gas content at the time of eruption. Whereas the ribbon/rope bombs were determined to be the most viscous or contained a lesser gas content. Looking at the Southern Bomb Field site, it is dominated by large bombs that were during flight were molded into aerodynamic shapes. The Eastern Rim site is dominated by smaller bombs that appeared to be more liquid during the eruption. This difference in the two sites is a probable indication of at least two different eruptive events of different degrees of explosivity. Overall, aerodynamic bombs are more common and extend to greater distances from the presumed vent (up to 800 m), while very fluidal bombs are uncommon beyond 500 meters. Fluidal bombs (‘cow pie’, ‘ribbon’, ‘rope/spindle’) show a clear trend in decreasing size with distance from vent, whereas the size-distance trend is less dramatic for the aerodynamic bombs.
Tecolote Volcano in the Pinacate Volcanic Field in Mexico contains multiple vents within a horseshoe-shaped crater that have all produced various ejecta (Zawacki et al. 2019). The objectives of this research are to map ballistic distribution to understand the relationship between the source vent or vents and the bombs and ballistics that litter the region around Tecolote, and interpret the eruption conditions that ejected those bombs by using their distributions, morphologies, and fine-scale textures.
The findings of this work are that these bombs are apparently from the last stages of the eruption, succeeding the final lava flows. The interiors and exteriors of the bombs display different cooling rates which can are indicated by the fabric found within. Using this, certain characteristics of the bombs during eruption were extrapolated. The ‘cow pie’ bombs were determined to be the least viscous or contained a higher gas content at the time of eruption. Whereas the ribbon/rope bombs were determined to be the most viscous or contained a lesser gas content. Looking at the Southern Bomb Field site, it is dominated by large bombs that were during flight were molded into aerodynamic shapes. The Eastern Rim site is dominated by smaller bombs that appeared to be more liquid during the eruption. This difference in the two sites is a probable indication of at least two different eruptive events of different degrees of explosivity. Overall, aerodynamic bombs are more common and extend to greater distances from the presumed vent (up to 800 m), while very fluidal bombs are uncommon beyond 500 meters. Fluidal bombs (‘cow pie’, ‘ribbon’, ‘rope/spindle’) show a clear trend in decreasing size with distance from vent, whereas the size-distance trend is less dramatic for the aerodynamic bombs.
ContributorsWest, Jacob Alexander (Co-author) / West, Jacob (Co-author) / Clarke, Amanda (Thesis director) / Arrowsmith, Ramon (Committee member) / Roggensack, Kurt (Committee member) / School of Earth and Space Exploration (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This study was conducted in order to determine whether the lagomorphs of 111 Ranch- Aztlanolagus agilis, Hypolagus arizonensis, and Sylvilagus cunicularius- could be distinguished based on femora. This is because while there is a large quantity of disarticulated lagomorph postcranial fossils from 111 Ranch, the chief diagnostic traits of A. agilis and H. arizonensis are the enamel patterns on their third premolars, leaving a large swath of specimens unidentifiable by diagnostic traits alone. Specimens from the Arizona Museum of Natural History were measured and compared to specimens known to be from these genera. Additionally, morphological traits in mandibles were used to identify mandible specimens, which in turn were used to identify fossils with the same specimen label. Statistical tests such as t-tests and principal components analyses were used to examine the distributions of sizes and locate clusters of datapoints likely corresponding to each genus. Some of these could be linked to a genus based on one particular specimen, P15156, which had been identified as Hypolagus based on its mandible morphology and size. The majority of the Museum'a specimens were thus associated with one of the three species, save for those which were too damaged and intermediate in size to confidently categorize.
ContributorsTkacik, Stephanie Marie (Author) / Farmer, Jack (Thesis director) / Reed, Kaye (Committee member) / McCord, Robert (Committee member) / School of Earth and Space Exploration (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05