Collection Description

The Department of Geological Sciences has a long-standing Senior Thesis research option for the B.S. Degree which involves a written thesis, and a public oral presentation done under the supervision of a faculty member. These independent research projects typically involve field work and laboratory analyses of samples, but can also include laboratory-based experimental projects, numerical modeling of geologic phenomena and literature reviews. Senior theses are kept in the permanent collection of the Malcolm A. Love Library on the SDSU campus.

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Estimation of stratoform cloud top height from NOAA-11 and NOAA-12 AVHRR Data
A method for estimating the height of the marine layer by use of satellite radiance temperatures using NOAA-11 and NOAA-12 AVHRR (Advanced Very High Resolution Radiometer) channel 4 images is proposed. The marine lay er top and cloud top are at the base of a temperature inversion. The height of the base of the inversion is obtained from in-situ measurements. Correlation of the inversion base height and the satellite radiance temperature then provides a means for estimating the cloud heights from satellite IA images. Once the correlation is established, the absolute height of the marine layer can be estimated over a large areal extent using satellite IA images. In theory, the relative height of the marine layer can be estimated by use of cloud top temperatures as higher cloud tops will radiate at longer wavelengths (lower temperature) and vice versa; however, with the small data set available for this study this could not be verified. with radiosonde (in-situ) data. With this correlation, we will have a useful tool for determining relative cloud top heights from digitized satellite photos. This method is particularly useful when radiosonde data is lacking or one needs to determine cloud top heights over a large areal extent., San Diego State University
Evaluating background levels for specific metals in San Diego Bay: A geochemical approach
Once pollution has been discovered in San Diego Bay, the San Diego Regional Water Quality Control Board (San Diego Water Board) is required by law to require the discharger to clean up that site to background conditions. However, the legislature does not quantify background levels for contaminants. To help the San Diego Water Board with this effort, this research measured the background levels for cadmium, copper, lead, and zinc within San Diego Bay. The methods used in this research were adopted from Myers and Thorbjornsens’ research techniques, which include the comparison of the trace metals to naturally occurring aluminum and/or iron. Results show background levels of .030 – .501 mg/kg for cadmium, 11.5 – 163 mg/kg for copper, 5 – 69.9 mg/kg for lead, and 36 – 431 mg/kg for zinc. Based on initial results, spatial patterns of background contaminant levels were identified. San Diego Bay has historically been divided into three geographic sections for the purposes of contaminant regulation (northern, central, and southern bay). Those three sections were evaluated to determine if the background for each trace element varied across the sections. Lead was the only trace metal that showed a pattern between the different geographic locations. In the central bay, lead had a higher concentration than the northern and southern sections. This is most likely due to high industrial activity in the central bay, but further research needs to be conducted. Cadmium showed no variations between the northern, central, and southern bay and the results show all levels of cadmium in the bay are natural background concentrations. Copper and zinc had similar results; both showed very little variation between the northern, central, and southern bay. Additionally, both copper and zinc had concentrations elevated above natural background levels in the industrial and marina locations. This pattern helped clarify where background concentrations existed in the bay for copper and zinc, and after plotting the industrial and marina locations versus the nonindustrial and non-marina locations, background levels for zinc and copper were established., San Diego State University
Evaluating geospatial learning in Earth Science
Geospatial reasoning is the ability to recognize the temporal & spatial interaction of properties, locations, and rates of change of earth's material reservoirs (solid earth, oceans, and atmosphere) in the generation of observed earth processes and phenomena. In order to increase effective teaching of system-scale thinking, one must first be able to assess geospatial reasoning as a result of instruction. The goals of this study are to evaluate the effectiveness of current web-based interfaces designed to increase geospatial reasoning, the quality of design features in such interfaces, and effectiveness of exercises used in conjunction with these interfaces. Several steps were taken to evaluate these components: utilization of a current interface (The GLOBE Program Earth system poster), creation and trial use of a new, inquiry-based classroom exercise to guide use of the interface, in-class observations, collection of completed exercises and test questions, construction of a key and rubric, and analysis of results. Our study design focused on the quality and detail of observations that resulted from student use of the interfaces and the depth and sophistication of student-generated explanations of those observations as a measure of learning gains from the exercises. "Observational" responses tend to be of average to low quality, and "explanation" responses are mostly low quality. "Explanation" style questions embedded into an exam yield better answers compared to the exercise. Misinterpretations of questions were common and the quality of answers between similar questions dropped as students progressed through the exercise. Students also showed a tendency to seek out and use physical globes to augment the computer­based interface during the exercise, even though the use of physical models was not an intended part of the exercise design. Low quality answers to "explanation" questions suggest the interface and exercise only modestly improved geospatial learning. The increase in scores from the exercise to the test shows that while some improvement in subject knowledge and understanding did occur, it is not immediately clear if these gains resulted from further reflection on the exercise, additional study, or reliance on other outside sources. Average to poor responses to observational questions and attachment to the physical globes indicates the interface is inadequate, lacking sufficiently high resolution in the presentation and of data and interactivity in the interface. Common misinterpretations and drops in scores between similar questions as the exercise progressed suggest disengagement and faults with the current structure of the in-class exercise. It is recommended that future interfaces should integrate higher quality data and allow a higher degree of student control. Disengagement and faults with the exercise suggest that further development and evaluation of classroom exercises is needed., San Diego State University
Evaluation of RiverTools GIS software for stream-profile analysis of the Irish Hills, San Luis Obispo County, California
The Diablo Canyon Nuclear Power Plant is located on the coast below the Irish Hills southwest of San Luis Obispo, CA. Built in 1973, the plant is operated by Pacific Gas and Electric (PG&E). In recent years, PG&E has been conducting a large-scale study of tectonic risks to the plant as part of their long term seismic program (LTSP). As part of that program, airborne LiDAR data were collected as a base for topographic evaluation of the landscape, and those data have been released to SDSU for this project. The Irish Hills are bounded by northwest-trending strike-slip and oblique to reverse faults, which curve westward both to the north and south of the hills. Movement of the Pacific plate toward the northwest is impeded by this bend, so the plate buckles. Fault slip in such a restraining bend generally leads to uplift of the compressed land surface. Evidence from coral dating suggests that marine terraces in the area have been uplifted at an average rate of about 0.2 mm per year for at least the past 120 ka. Another way of assessing vertical displacement is by analysis of drainage systems. Specifically, the drainage density within the Irish Hills is expected to be different to that in nearby less-uplifted regions. There should also be a regional change in the Hack index, also known as the stream-length gradient or SL index. If lithology, precipitation and other key factors are the same, we should expect to see greater drainage density and SL index values in a recently uplifted region than in a nearby region where uplift is less. If we do in fact see this, we may conclude that recent uplift is a reasonable factor to explain the differences in drainage parameters. For this project, a one-meter resolution LiDAR elevation model provided by PG&E was analyzed with RiverTools, a specialized geographic information systems (GIS) product designed to extract stream networks and related statistics from digital elevation models (DEMs). The extracted networks were exported to a vector format (ESRI shapefile) and spatially correlated with a one-kilometer square grid. The grid cells were coded to represent drainage density (total length of streams per square kilometer), SL index (values averaged over each square), and Horton-Strahler order, and overlaid on a regional map to display correlations between these values and regions of different uplift rate. Preliminary results show a definite signal along the crest of the Irish Hills with respect to drainage density. Results for SL index and HS order are less definitive., San Diego State University
Evaluation of drill cuttings for determination of formation change using particle-size analysis, San Diego, California
The Municipality of San Diego is reliant on imported water and is in need of control over future water supplies. Outside factors affecting imported supply are of growing concern; drought, periodic cutbacks and the potential for price increases are just some of the realities that have fueled the need for the exploration of new sources. Thus, in an effort to become less reliant on imported water, United States Geological Survey in cooperation with the City of San Diego has sought to investigate the feasibility of using groundwater aquifers, in particular the San Diego Formation and its overlying and underlying units as possible sources of groundwater. This study focuses on a quantitative approach to delineate subsurface formations using drill cuttings. The analysis was conducted using digital image processing to determine grain-size distributions of samples taken at various depths of a single water test well at the intersection of Home and Federal Boulevard. The data were then analyzed and correlated to asses formation changes in the subsurface. These quantitative data delineated formations that were consistent with geophysical logs, thereby aiding in the effort to better understand the hydrogeology of subsurface San Diego. The data are consistent with the 6 known subsurface formations: San Diego Fm., Stadium Cong., Mission Valley Fm., Poway Cong., Otay Fm, and Friars Fm. Because the drill cuttings lack formation clay and silt, the sediment-size analysis is skewed to providing useful information about sand, granule, and gravel components., San Diego State University
Evidence for mid-tertiary extension on Santa Catalina Island and its disruption of mesozoic tectonic and metamorphic features
Catalina conclusively exhibits evidence for extension in the Miocene. Normal faulting, dikes, and sills, associated with extension, have been correlated to have occured during the emplacement of the Catalina pluton. Locally observed extension and intrusion may be products of larger regional extension, which is similar to other crustal extension forming basins in the southern California region. These basins, located throughout southern California, have been the site of large mineral explorations. Catalina extension maybe further correlated with crustal extension observed in the Colorado River area that has exposed large blocks of Orocopia Schist and its' related units. Tertiary extension has produced major disruption of Mesozoic tectonic and metamorphic features. This requires that Tertiary extension be removed from these older features before they can be interrelated., San Diego State University
Examining fault scarps in the Yuha Desert, to determine if they were caused by the 1892 Laguna Salada Earthquake
The most recent large Laguna Salada fault rupture occurred at 23:20 Pacific Standard Time on February 23, 1892 and exhibited oblique normal-dextral slip. The moment magnitude was estimated to be Mw7.2, with maximum intensity (MMI) of X in the western Imperial Valley and VII (Severe) in San Diego. This fault exhibited about 55 km of surface faulting, with horizontal displacement as large as 4 m and dip slip as high as 5 m. To further examine the extent of this earthquake, a pair of fault scarps in the Yuha Desert that were suspected as possibly having ruptured in 1892 were chosen to examine. These scarps were chosen because on aerial imagery, they could be seen crossing late Quaternary alluvium, and thus were suspected to be young. They were analyzed by first profiling the scarps, followed by calculations of the scarp ages using diffusion modeling. Finally, scarp profiles were compared to data from known examples of surface ruptures of the 1892 earthquake. It was ascertained that both scarps were possibly a result of the 1892 earthquake or one of its aftershocks., San Diego State University
Exploring magnetotelluric data as a geothermal assessment tool in the Caja del Rio near Santa Fe, New Mexico
Magnetotelluric (MT) data collected during June 2011 at Summer of Applied Geophysical Experience (SAGE) was used as a geothermal assessment tool in the Caja del Rio. This area is part of the Cerros del Rio volcanic field in the Rio Grande rift approximately 25 km northwest of Santa Fe, New Mexico. Geothermal indicators nearby include exposed vents, high 3He/4He ratios in the groundwater, rift related faults, and a 58°C/km thermal gradient (Manning, 2009)which slightly exceeds thermal gradients measured in Albuquerque, New Mexico over comparable depths. We present one-dimensional inversion models of the MT data collected from four sites by SAGE 2011 in the Caja del Rio area. The models suggest a depth of 2 km to the basement, in agreement with previous models supporting water-bearing Santa Fe Group sediments above a low-porosity, impermeable basement rock. The 2011 SAGE MT data was also used to estimate the depths of a mid-crustal conductor ranging from 10 to 14 km. We propose to extend the interpretation by Wannamaker et al. (2008) that a mid-crustal conductor for the Eastern Great Basin represents the 500°C isotherm, to the Caja del Rio area. This analysis supports geothermal prospects by explaining in part the high thermal gradients in the Caja del Rio., San Diego State University
Fault zone architecture near the SE termination of the Powerline Fault, Ocotillo Wells OHV, SE California
Pliocene-Pleistocene sedimentary rocks of the Salton Basin, SE California have long been recognized for their complicated fold and fault fabric and the role that strike-slip faults of the San Andreas system have played in the development of this fabric. However, few studies have focused on characterizing structures developed immediately adjacent to individual strike-slip faults. Hence, I undertook a study of a small area located near the termination of the Powerline fault in the Ocotillo Wells State Vehicular Recreation Area. Three informal lithostratigraphic units were defined within the study area. These units, from youngest to oldest, are as follows: mudstone, sandstone with centimeter meter sized calcareous concretions, and platy sandstone. These units are wrapped about an E-W trending syncline (the Powerline syncline), and are cut by a high angle reverse fault (the southern reverse fault) that broke through the former position of an anticline. Another high angle reverse fault (the northern reverse fault) places generally unfolded units below the Powerline syncline and southern reverse fault. The Powerline syncline and southern reverse fault are bounded by a NE trending sinistral strike-slip fault to the west and a N-W trending dextral strike-slip fault to the east, and appear to represent a high strain zone located adjacent to the Powerline fault. In order to characterize the geometry of the Powerline syncline, a detailed stereonet analysis of the fold along three cross sections was evaluated. The first step was to determine the average attitude of bedding making up the northern and southern limbs along each cross section. To complete this task, poles to beds making up each limb were plotted and then contoured using the program StereoNet. The resulting average attitude for each limb was then used to find the interlimb angle, attitude of the axial surface, and plunge of the syncline along each of the three cross sections. Resulting data indicate that the syncline ranges from open to tight, upright to steeply inclined, and gently plunging to sub-horizontal. The interlimb angle varies from 89° to 128°, the dip of the axial surface from 69° to 89°, and the plunge from 27° to 1° to the east. Cutting the Powerline syncline, and northern and southern reverse faults is a set of conjugate NW striking dextral and NE striking sinistral faults. A geometrical evaluation of the strikes of this conjugate fault system revealed that the maximum principal stress direction during their formation was likely oriented ~N8E. This orientation is also consistent with the shortening direction indicated by the Powerline fault, and the northern and southern reverse faults. Hence, the fault-fold fabric near the SE termination of the Powerline fault appears to be governed by Andersonian principles., San Diego State University
Field and petrochemical description of the Mount Calavera Volcanic Dome, Carlsbad, California
Mount Calavera is a small volcanic feature in northeastern Carlsbad, CA. It has not been radiometrically dated, but its relative age is apparent in that it crosscuts the Cretaceous Green Valley tonalite and appears to crosscut or overlie the Eocene Santiago Formation. Since Late Oligocene to Miocene volcanism was fairly common in southern California, this seems like a reasonable age range for Mount Calavera. Volcanism during this time has been attributed to a trans-tensional environment which developed in the aftermath of the collision of the Farallon spreading center with the North American oceanic trench. The rotation of crustal blocks during this time led to the development of zones of weakened crust, allowing easy access for volcanic production throughout the California Borderlands. Major-element chemistry demonstrates that Mount Calavera is a high-silica andesite with low Fe typical of calc-alkaline differentiation, characteristics that it shares with many of the Borderlands analyses; however, unlike the Borderland volcanics, Mount Calavera has a strong adakite signature, suggesting that it may have been derived from direct melting of oceanic crust, or a similar mafic source rock. Mount Calavera has been variably described as a stock, plug, or a volcano by other workers. A stock or plug defines a shallow intrusion or endogenous dome, but field characteristics are more suggestive of an exogenous (extruded) feature. There is no indication that Mt. Calavera is a volcano, and it lacks volcanic deposits typical of a volcanic edifice. Instead, its field characteristics are consistent with the diapiric extrusion of an isolated, monogenic lava dome., San Diego State University
First study of coreston-saprock development within NE-block San Jacinto Fault, Anza, California; Implications for the genesis of clastic sediment derived from granodiorite-quartz monzodiorite
Weathering, erosion, and sorting during transportation in the fluvial regime play important integrated roles in the development of quartzofeldspathic sediment. For example, H. W. Nesbitt and colleagues showed that sorting of eroded regolithic material produces a mud-rich component that is more weathered than sand derived from the same source. In order to test this idea, I collected 5 corestone samples and 5 saprock samples from a single site located east of the Clark segment of the San Jacinto fault, SE of Anza, California. Each of the five saprock samples was split into two parts. One part was used as the bulk sample, while the other part was sieved into the following size fractions: >63 microns, 63-45 microns, and <45 microns. Utilizing the XRF facilities at SDSU each sample was analyzed for its major element composition. The corestone is an equigranular hypidiomorphic granodiorite to quartz monzodiorite. In p(A)-p(CN)-p(K) space chemical data derived from corestone and bulk saprock samples spread about a linear trend with saprock samples plotting to the left of corestone samples. Non-central principal component analysis and the linear compositional modeling techniques of H. von Eynatten and colleagues, show that PC1 explains 96.4% of the variability in the calculated linear trend. Using orthogonal projection, weathering intensity factors were calculated for the bulk saprock samples. They ranged from 0.04 to 0.14. Utilizing Al as a reference frame, mass balance calculations indicated that 11% (+6%/-7%) of the mass of K and 15% (± 4%) of the mass of P was lost during the conversion of corestone to bulk saprock. Such losses reflect the alteration of biotite and apatite respectively. In addition, a nominally small increase of Si mass (5% ± 3%) is evident. Thus, both the weathering intensity factors and the mass balance calculations indicate that the bulk saprock samples are poorly weathered, and that the loss of K mass from biotite is a major controlling factor. If erosion removed the regolith at the study site, and fluvial processes size fractionated the resulting sediment, then the >63 micron fraction would be sorted into sand and pebble sized material, while the 63-45 micron fraction would represent coarse silt. The <45 micron fraction would include medium and fine silt along with clay-sized materials. On a p(A)-p(CN)-p(K) ternary diagram, the sieved fractions plot about a linear compositional trend that is similar to that derived solely from the corestone and bulk saprock samples. Moreover, the >63 micron fractions plot at the lower end of this trend while the finer grained fractions plot about the trend but nearer the p(A)-p(CN) join. Weathering intensity factors for the two 45-63 micron fractions are 0.86 and 0.95 while weathering intensity factors for the three <45 micron fractions are 0.85, 0.97, and 0.95. These results contrast markedly with those provided above for the bulk saprock samples, and clearly indicate that the sieved finer grained fractions captured a part of the weathering trend that is masked by the bulk saprock samples. In short, the results of this study document for the first time, a trend derived from the weathering of granodiorite to quartz monzodiorite that is controlled primarily by the loss of K from biotite. This trend has not been previously recognized but given that the composition of the corestone studied during this investigation is relatively common in eroded continental margin magmatic arcs on a global basis it may be more widespread than currently recognized. Clearly more work is warranted., San Diego State University