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- All Subjects: geology
- Creators: School of Earth and Space Exploration
Description
A wide range of types of activity in mid-latitude Martian gullies has been observed over the last decade (Malin et al., 2006; Harrison et al., 2009, 2015; Diniega et al., 2010; Dundas et al., 2010, 2012, 2015, 2017) with some activity constrained temporally to occur in the coldest times of year (winter and spring; Harrison et al., 2009; Diniega et al., 2010; Dundas et al., 2010, 2012, 2015, 2017), suggesting that surficial frosts that form seasonally and diurnally might play a key role in this present-day activity. Frost formation is highly dependent on two key factors: (1) surface temperature and (2) the atmospheric partial pressure of the condensable gas (Kieffer, 1968). The Martian atmosphere is primarily composed of CO2and CO2 frost formation is not diffusion-limited (unlike H2O). Hence, for temperatures less than the local frost point of CO2, (~ 148 K at a surface pressure of 610 Pa) frost is always present (Piqueux et al., 2016). Typically, these frosts are dominated volumetrically by CO2, although small amounts of H2O frosts are also present, and typically precede CO2 frost deposition (due to water’s higher condensation temperature (Schorghofer and Edgett, 2006)). Here we use the Thermal Emission Imaging System (THEMIS) and the Thermal Emission Spectrometer (TES) onboard Mars Odyssey and Mars Global Surveyor, respectively, to explore the global spatial and temporal variation of temperatures conducive to CO2 and H2O frost formation on Mars, and assess their distribution with gully landforms. CO2 frost temperatures are observed at all latitudes and are strongly correlated with dusty, low thermal inertia regions near the equator. Modeling results suggest that frost formation is restricted to the surface due to near-surface radiative effects. About 49 % of all gullies lie within THEMIS frost framelets. In terms of active gullies, 54 % of active gullies lie within THEMIS framelets, with 14.3% in the north and 54% in the south.
Relatively small amounts of H2O frost (~ 10–100 μm) are also likely to form diurnally and seasonally. The global H2O frost point distribution follows water vapor column abundance closely, with a weak correlation with local surface pressure. There is a strong hemispherical dependence on the frost point temperature—with the northern hemisphere having a higher frost point (in general) than the southern hemisphere—likely due to elevation differences. Unlike the distribution of CO2 frost temperatures, there is little to no correlation with surface thermophysical properties (thermal inertia, albedo, etc.). Modeling suggests H2O frosts can briefly attain melting point temperatures for a few hours if present under thin layers of dust, and can perhaps play a role in present-day equatorial mass-wasting events (eg. McEwen et al., 2018).
Based on seasonal constraints on gully activity timing, preliminary field studies, frost presence from visible imagery, spectral data and thermal data (this work), it is likely that most present-day activity can be explained by frosts (primarily CO2, and possibly H2O). We predict that the conditions necessary for significant present-day activity include formation of sufficient amounts of frost (> ~20 cm/year) within loose, unconsolidated sediments (I < ~ 350) on available slopes. However, whether or not present-day gully activity is representative of gully formation as a whole is still open to debate, and the details on CO2 frost-induced gully formation mechanisms remain unresolved.
Relatively small amounts of H2O frost (~ 10–100 μm) are also likely to form diurnally and seasonally. The global H2O frost point distribution follows water vapor column abundance closely, with a weak correlation with local surface pressure. There is a strong hemispherical dependence on the frost point temperature—with the northern hemisphere having a higher frost point (in general) than the southern hemisphere—likely due to elevation differences. Unlike the distribution of CO2 frost temperatures, there is little to no correlation with surface thermophysical properties (thermal inertia, albedo, etc.). Modeling suggests H2O frosts can briefly attain melting point temperatures for a few hours if present under thin layers of dust, and can perhaps play a role in present-day equatorial mass-wasting events (eg. McEwen et al., 2018).
Based on seasonal constraints on gully activity timing, preliminary field studies, frost presence from visible imagery, spectral data and thermal data (this work), it is likely that most present-day activity can be explained by frosts (primarily CO2, and possibly H2O). We predict that the conditions necessary for significant present-day activity include formation of sufficient amounts of frost (> ~20 cm/year) within loose, unconsolidated sediments (I < ~ 350) on available slopes. However, whether or not present-day gully activity is representative of gully formation as a whole is still open to debate, and the details on CO2 frost-induced gully formation mechanisms remain unresolved.
ContributorsKhuller, Aditya Rai (Author) / Christensen, Philip (Thesis director) / Harrison, Tanya (Committee member) / Diniega, Serina (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Galaxies in the universe are surrounded by a hot medium called the Circum-Galactic Medium (CGM). Present the CGM is gas that forms up clouds which travel within the CGM at speeds that approximately range between 100 km/s and 300 km/s. These gas clouds are very interesting because they play a crucial in the formation of stars within the galaxies and also in the overall evolution of galaxies. The clouds could in fact be thought of as mobile "gas stations" whose sole purpose is facilitate the ionization of elements and ultimately supply gas to galaxies. My thesis project is a follow-up study on CGM gas cloud observations that were made by Borthakur et. al. (2016). Using Cosmic Origins Spectrograph (COS) data from the Hubble Space Telescope (HST), Borthakur et. al. (2016) observed the presence of both Carbon IV (C IV) and Oxygen VI (O IV) but did not observe any Nitrogen V (N V) in the gas cloud when expected to be observable. Therefore, the ultimate goal of my research was to determine whether indeed CGM gas clouds have an actual shortage of the N V ion. My research involves the generation of cosmological simulations of a cold gas cloud that has a radius of 98 parsecs, relative velocity of 200 km/s, density range of 10-3 to -5 and a temperature in the range of ~104 to 5 K, and also a hot CGM that has density in the range of 10-4.5 to -6 particles/cm3 and temperature of approximately 106 K. Traces of N v are observed in my simulations.
ContributorsSaboi, Kezman (Author) / Scannapieco, Evan (Thesis director) / Borthakur, Sanchayeeta (Committee member) / Cottle, JNeil (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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
Lactase persistence is the ability of adults to digest lactose in milk (Segurel & Bon, 2017). Mammals are generally distinguished by their mammary glands which gives females the ability to produce milk and feed their newborn children. The new born therefore requires the ability to breakdown the lactose in the milk to ensure its proper digestion (Segurel & Bon, 2017). Generally, humans lose the expression of lactase after weaning, which prevents them being able to breakdown lactose from dairy (Flatz, 1987).
My research is focused on the people of Turkana, a human pastoral population inhabiting Northwest Kenya. The people of Turkana are Nilotic people that are native to the Turkana district. There are currently no conclusive studies done on evidence for genetic lactase persistence in Turkana. Therefore, my research will be on the evolution of lactase persistence in the people of Turkana. The goal of this project is to investigate the evolutionary history of two genes with known involvement in lactase persistence, LCT and MCM6, in the Turkana. Variants in these genes have previously been identified to result in the ability to digest lactose post-weaning age. Furthermore, an additional study found that a closely related population to the Turkana, the Massai, showed stronger signals of recent selection for lactase persistence than Europeans in these genes. My goal is to characterize known variants associated with lactase persistence by calculating their allele frequencies in the Turkana and conduct selection scans to determine if LCT/MCM6 show signatures of positive selection. In doing this, we conducted a pilot study consisting of 10 female Turkana individuals and 10 females from four different populations from the 1000 genomes project namely: the Yoruba in Ibadan, Nigeria (YRI); Luhya in Webuye, Kenya; Utah Residents with Northern and Western European Ancestry (CEU); and the Southern Han Chinese. The allele frequency calculation suggested that the CEU (Utah Residents with Northern and Western European Ancestry) population had a higher lactase persistence associated allele frequency than all the other populations analyzed here, including the Turkana population. Our Tajima’s D calculations and analysis suggested that both the Turkana population and the four haplotype map populations shows signatures of positive selection in the same region. The iHS selection scans we conducted to detect signatures of positive selection on all five populations showed that the Southern Han Chinese (CHS), the LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations had stronger signatures of positive selection than the Turkana population. The LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations showed the strongest signatures of positive selection in this region. This project serves as a first step in the investigation of lactase persistence in the Turkana population and its evolution over time.
My research is focused on the people of Turkana, a human pastoral population inhabiting Northwest Kenya. The people of Turkana are Nilotic people that are native to the Turkana district. There are currently no conclusive studies done on evidence for genetic lactase persistence in Turkana. Therefore, my research will be on the evolution of lactase persistence in the people of Turkana. The goal of this project is to investigate the evolutionary history of two genes with known involvement in lactase persistence, LCT and MCM6, in the Turkana. Variants in these genes have previously been identified to result in the ability to digest lactose post-weaning age. Furthermore, an additional study found that a closely related population to the Turkana, the Massai, showed stronger signals of recent selection for lactase persistence than Europeans in these genes. My goal is to characterize known variants associated with lactase persistence by calculating their allele frequencies in the Turkana and conduct selection scans to determine if LCT/MCM6 show signatures of positive selection. In doing this, we conducted a pilot study consisting of 10 female Turkana individuals and 10 females from four different populations from the 1000 genomes project namely: the Yoruba in Ibadan, Nigeria (YRI); Luhya in Webuye, Kenya; Utah Residents with Northern and Western European Ancestry (CEU); and the Southern Han Chinese. The allele frequency calculation suggested that the CEU (Utah Residents with Northern and Western European Ancestry) population had a higher lactase persistence associated allele frequency than all the other populations analyzed here, including the Turkana population. Our Tajima’s D calculations and analysis suggested that both the Turkana population and the four haplotype map populations shows signatures of positive selection in the same region. The iHS selection scans we conducted to detect signatures of positive selection on all five populations showed that the Southern Han Chinese (CHS), the LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations had stronger signatures of positive selection than the Turkana population. The LWK (Luhya in Webuye, Kenya) and the YRI (Yoruba in Ibadan, Nigeria) populations showed the strongest signatures of positive selection in this region. This project serves as a first step in the investigation of lactase persistence in the Turkana population and its evolution over time.
ContributorsJobe, Ndey Bassin (Author) / Wilson Sayres, Melissa (Thesis director) / Paaijmans, Krijn (Committee member) / Taravella, Angela (Committee member) / School of Earth and Space Exploration (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
For the geoscience community to continue to grow, students need to be attracted to the field. Here we examine the Incorporated Research Institutions for Seismology (IRIS) Research Experience for Undergraduates (REU) program to understand how the participants' experiences' affects their interest in geoscience and educational and career goals. Eleven interns over two years (2013-2014) were interviewed prior to the start of their internship, after their internship, and after presenting their research at the American Geophysical Union annual meeting. This internship program is of particular interest because many of the interns come into the REU with non-geoscience or geophysics backgrounds (e.g., physics, mathematics, chemistry, engineering). Both a priori and emergent codes are used to convert interview transcripts into quantitative data, which is analyzed alongside demographic information to understand how the REU influences their decisions. Increases in self-efficacy and exposure to multiple facets of geoscience research are expressed as primary factors that help shape their future educational and career goals. Other factors such as networking opportunities and connections during the REU also can play a role in their decision. Overall, REU participants who identified as geosciences majors solidified their decisions to pursue a career in geosciences, while participants who identified as non-geosciences majors were inclined to change majors, pursue geosciences in graduate school, or explore other job opportunities in the geosciences.
ContributorsGossard, Trey Marshall (Author) / Semken, Steven (Thesis director) / Garnero, Edward (Committee member) / Reynolds, Stephen (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Blue Mound State Park, located in the state of Wisconsin (USA), is host to a topographic anomaly known as Blue Mound. This mound is the western of the two mounds that make up the park, and it marks the highest elevation in southern Wisconsin. Unlike its eastern sibling, Blue Mound possesses an unusual chert cap that may have protected it from erosion, thus preserving its stratigraphic integrity. Although Blue Mound's unique chert armor was noted in 1927 by the Wisconsin Geological and Natural History Survey, no published work has satisfactorily explained its origin. As little was known about the formation of cherts until the mid-to-late 1900s, the Blue Mound cap was classified merely as a Silurian dolostone into which chert had somehow become integrated (Steidtmann). However, the published observations of the Blue Mound chert do not necessarily match with the classification granted by the Wisconsin Geological and Natural History Survey, nor were any convincing interpretations offered regarding the presence of the chert. Since 1927, significant progress in the field of sedimentology has been achieved. There now exists knowledge that may fill the gaps between observation and interpretation in the Blue Mound survey. The observations in the 1927 bulletin correspond with modern notions of a paleokarst chert breccia, which forms a chert rubble or residuum. A chert breccia is formed when existing clasts, or pieces, of chert become cemented together by further chert deposition (Kolodny, Chaussidon and Katz). This can form large boulders of chert rubble that resist erosion. Accumulation of chert rubble has been documented to form along old weathering surfaces as an insoluble residue in environments similar to Blue Mound (Kolodny, Chaussidon and Katz). The purpose of this investigation was to verify the observations within the 1927 survey of the Blue Mound chert, and determine through field observations and sample study if the Blue Mound chert fits the model of a paleokarst chert breccia.
ContributorsGalarowicz, Calley (Author) / Knauth, Paul (Thesis director) / Semken, Steven (Committee member) / Martin, Thomas (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2013-05
Description
Stellar mass loss has a high impact on the overall evolution of a star. The amount<br/>of mass lost during a star’s lifetime dictates which remnant will be left behind and how<br/>the circumstellar environment will be affected. Several rates of mass loss have been<br/>proposed for use in stellar evolution codes, yielding discrepant results from codes using<br/>different rates. In this paper, I compare the effect of varying the mass loss rate in the<br/>stellar evolution code TYCHO on the initial-final mass relation. I computed four sets of<br/>models with varying mass loss rates and metallicities. Due to a large number of models<br/>reaching the luminous blue variable stage, only the two lower metallicity groups were<br/>considered. Their mass loss was analyzed using Python. Luminosity, temperature, and<br/>radius were also compared. The initial-final mass relation plots showed that in the 1/10<br/>solar metallicity case, reducing the mass loss rate tended to increase the dependence of final mass on initial mass. The limited nature of these results implies a need for further study into the effects of using different mass loss rates in the code TYCHO.
ContributorsAuchterlonie, Lauren (Author) / Young, Patrick (Thesis director) / Shkolnik, Evgenya (Committee member) / Starrfield, Sumner (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Papago Park in Tempe, Arizona (USA) is host to several buttes composed of landslide breccias. The focus of this thesis is a butte called “Contact Hill,” which is composed of metarhyolitic debris flows, granitic debris flows, and Barnes Butte Breccia. The Barnes Butte Breccia can be broken down into several different compositional categories that can be dated based on their relative ages. The depositional timeline of these rocks is explored through their mineral and physical properties. The rhyolitic debris flow is massively bedded and dips at 26° to the southeast. The granitic debris flow is not bedded and exhibits a mixture of granite clasts of different grain sizes. In thin section analysis, five mineral types were identified: opaque inclusions, white quartz, anhedral and subhedral biotite, yellow stained K-feldspar, and gray plagioclase. It is hypothesized that regional stretching and compression of the crust, accompanied with magmatism, helped bring the metarhyolite and granite to the surface. Domino-like fault blocks caused large brecciation, and collapse of a nearby quartzite and granite mountain helped create the Barnes Butte Breccia: a combination of quartzite, metarhyolite, and granite clasts. Evidence of Papago Park’s ancient terrestrial history is seen in metarhyolite clasts containing sand grains. These geologic events, in addition to erosion, are responsible for Papago Park’s unique appearance today.
ContributorsScheller, Jessica Rose (Author) / Reynolds, Stephen (Thesis director) / Johnson, Julia (Committee member) / School of Earth and Space Exploration (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Hydraulic fracturing, or fracking, has become a common practice in United States oil fields for enhancing their productivity. Among the concerns regarding fracking, however, is the possibility that it could trigger shallow earthquakes. The brine that results from fracking is injected into the subsurface for disposal. This brine causes a pore pressure gradient that is commonly believed to trigger failure along critically stressed subsurface faults. In Timpson, a small city in eastern Texas, earthquakes have become much more common since two injection wells were installed in 2007. 16 events of M_W > 2 have been detected since 2008 and are believed to be associated with failure along a subsurface fault. Applying interferometric synthetic aperture radar, we analyzed 3 sets of SAR images from the Advanced Land Observing Satellite (ALOS) from May 2007 to December 2010. Using these data sets, XX interferograms were generated. From these interferograms, it was possible to determine the spatial and temporal evolution of the crustal deformation in the line-of-sight of the satellite. The results show strong evidence of uplift in the region adjacent to the injection wells. While previous studies have established a strong connection between fluid injection and increased seismicity, this is to our knowledge the first observed case of crustal deformation that has been observed as a result of hydraulic fracturing fluid disposal.
ContributorsSedlak, Alexander Paul Woodward (Author) / Shirzaei, Manoochehr (Thesis director) / Vivoni, Enrique (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Geographical Sciences and Urban Planning (Contributor) / School of Earth and Space Exploration (Contributor)
Created2014-05
Description
Many radioactive decay schemes employed in geochronology prove imprecise when placing accurate age constraints on young basalt flows. The (U-Th)/He systematics of detrital zircon and apatite within baked zones is examined as an alternative. Parent-daughter radioisotope ratios within grains from baked zones can completely reset if subjected to temperatures high enough and long enough for bulk diffusive loss. Presented here is the reproducibility of initial attempts to date flows by examining the (U-Th)/He geochronology of grains within baked zones. We examine grains from two localities within the San Francisco Volcanic Field and the Mormon Volcanic Field in northern Arizona. Thirteen zircon and apatite grains yielded from locality 2 collected from the uppermost 10 cm beneath a 7m flow of a basalt yield an apparent age of 4.39 ± 0.28 Ma (2σ), which is within range of published Middle Pliocene ages. Twenty-nine grains from locality 1 collected from the uppermost 20 cm beneath a 2 to 5m flow yield dates ranging from 0.47 ± 0.02 Ma to 892.77 ± 27.02 Ma, indicating the grains were partially reset or not reset at all. The degree to which grains are reset depends on a variety of factors detailed in this study. With these factors accounted for however, our study confirms application of this indirect dating technique is a useful tool for dating basaltic flows.
ContributorsCronk, Stephanie Sarah (Author) / Hodges, Kip (Thesis director) / van Soest, Matthijs (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2014-05