Senior Theses (School of Earth Sciences)
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During the senior year or with senior ranking, students pursuing the BS degree in Earth Sciences are required to undertake a senior research project with faculty supervision and to submit a letter-graded senior thesis report of professional quality to the Earth Sciences 4999.01 senior thesis faculty supervisor before graduation. Honors majors theses are also submitted to the honors program as Earth Sciences 4999.01H honors theses. Students pursuing the BA degree in Earth Sciences may also do a senior thesis, following the same procedures. A faculty committee reviews all submitted theses to select the Undergraduate Senior Research Award for that year. A bound paper copy of each submitted and graded thesis is deposited in the Orton Memorial Library of Geology.
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Item Reinvestigation of a Giant Ground Sloth Site, Holmes County, Ohio(The Ohio State University, 2023-08) Idzakovich, Matthew; Babcock, LorenA skeleton of the giant ground sloth Megalonyx jeffersonii was excavated from a farm in Holmes County, Ohio, in 1890. It was mounted and installed in the Orton Geological Museum at The Ohio State University in 1896. The exact location of the excavation has been somewhat ambiguous. Using a combination of contemporary reports, geologic studies, and satellite information, the excavation site in Berlin Township, Holmes County, Ohio, has been identified. In the process of trying to identify the excavation site, new information about the skeleton including how the mount was constructed has come to light.Item DETERMINATION OF OXYGEN FUGACITY USING OLIVINE-MELT EQUILIBRIUM: IMPLICATIONS FOR THE REDOX STATES OF VOLCANIC ARC BASALT MANTLE SOURCE REGIONS(The Ohio State University, 2019-05) Bryson, Seth; Barton, MichaelIn order to connect volcanic rocks to their mantle sources, it is essential to consider redox equilibria and their dependence on temperature, pressure, chemical composition, and oxygen fugacity. Oxygen fugacity (fO2) is an intensive variable that affects the behavior of those elements in magmas that are sensitive to changes in redox state, such as Fe, and therefore Mg-Fe silicates, such as olivine. Since fO2 plays an important role in fractional crystallization, in principle it is possible to estimate fO2 from analyses of olivine in equilibrium with the melt. This research describes a new method based on this principle called the Olivine-Melt Equilibrium Method. The Fe3+ and Fe2+ contents of melt in equilibrium with olivine are calculated from a relationship that describes the partitioning of Mg and Fe2+ between olivine and melt. The Fe3+ and Fe2+ contents of the melt are then used to calculate the fO2 at which olivine and melt are in equilibrium using a model for the relationship between Fe3+/Fe2+, fO2, T, P, and melt composition. Calculated oxygen fugacities from published analyses of coexisting melt and olivine pairs in samples from volcanic arc geological settings are being used to examine the effects of recycling on redox state. Calculations provide ΔFMQ = +1.03 ± 0.52 for olivine-melt pairs from Sunda arc basalts, ΔFMQ = +1.50 ± 0.70 for the Mariana Islands and ΔFMQ = +1.37 ± 0.79 for the Cascades. However it is necessary to evaluate the possibility that fO2 changes during magma ascent before concluding that the oxygen fugacities of erupted magmas directly reflect those of the mantle source regions.Item The Impact of Climate Change on Two Scenic Rivers In Ohio(The Ohio State University, 2024-12) Green, Melody; Lyons, W. BerryIn the state of Ohio, most rivers have undergone major modifications due to human activity. Fifteen rivers across the state have retained most of their natural character and are designated as scenic rivers. These rivers are ideal surface water systems to characterize hydrologic shifts caused by changes in climate. This work is an assessment of the impact of climate change on two scenic rivers in northeast and central Ohio, the Grand River and Darby Creek. Discharge and precipitation data over a 31-year period were collected and statistical analyses were conducted using the Mann-Kendall Test to evaluate trends in the data. Annual and monthly trends revealed an increase in annual mean, median, and maximum discharge, and a decrease in annual minimum discharge. Overall, it is evident that river discharge increased from 1990 to 2021. Higher annual maximums and lower minimums suggest an increase in extreme weather events that can cause floods and droughts. Additional statistical analyses conducted on Ohio precipitation revealed a decrease in total precipitation, in contrast with findings from similar research. Data on El Niño Southern Oscillation was collected to investigate the correlation between discharge and short-term climate cycles. The discharge patterns of the Grand River and Darby Creek suggest long-term changes, which may be representative of fluctuating precipitation and climate over time. Along with climate, long-term changes are likely reflective of shifts in land use. These data are important to understand how hydrologic patterns are shifting due to changes in climate, as both environmental and human systems are threatened by increasing erosion changes and flooding events.Item Solar Charger Telemetry Acquisition from Remote Measuring Stations(The Ohio State University, 2024-12) McCatherine, Nicholas; Gomez, DemianThis thesis focuses on the development and implementation of telemetry acquisition software for a remote geodetic measurement station powered by solar energy. Using a Raspberry Pi, the system integrates a Victron SmartSolar MPPT Controller to monitor solar panel and battery performance. Communication is facilitated through the Bluetooth Low Energy transceiver on the Raspberry Pi, with data parsing and decryption handled by the software. Simulations were conducted to predict power output under ideal conditions, and real-world testing validated the systems functionality. Results highlight the system’s ability to provide insights into battery health and system status and can help in diagnosing issues remotely without the need for physical inspection. This thesis also identifies limitations in telemetry resolution and challenges with decrypting and parsing the data and suggests areas for refinement. Future work would focus on expanding the compatibility of the program to devices from other manufacturers and exploring developing a fully open-sourced MPPT charge controller.Item Evaluating the Accuracy of Surface Water and Ocean Topography (SWOT) Satellite Measurements for River Water Surface Elevation Anomalies(The Ohio State University, 2024-12) Robinson, Robert, III; Durand, MichaelThis study was conducted to test the accuracy and water surface elevation anomalies of the Surface Water and Ocean Topography (SWOT) satellite remote sensing measurements to USGS gauges located across four rivers, the Olentangy, Ohio, Maumee, and Muskingum from August 2023 to August 2024. To compare these anomalies, a Jupyter Lab notebook was created to gather the data from four different SWOT reaches, and USGS gauges to create a table of water surface elevation time series. Before the SWOT data can be plotted together, a filter is needed to distinguish the bad-quality data from the good-quality data the satellite may have collected. Two plots were created for each river, filtered SWOT data with USGS gauge data and unfiltered SWOT data with USGS gauge data. Unfiltered is all the data that the SWOT time series outputs. After filtering the SWOT data, it is plotted with the USGS gauge data (after subtracting their initial values). All data from the Olentangy and Muskingum rivers was filtered out and deemed unsuitable for analysis. The Ohio River had an RMSE (root square mean error) value of 0.27 m and the Maumee River had an RMSE of 1.36 m. The RMSE pertains to the typical differences between the gauge and SWOT data. In conclusion, all river data undergoes filtering, but only a subset meets the necessary quality standards. From the available filtered data, the results exceed the scientific requirements.Item Particulate Organic Matter in the Scioto River(The Ohio State University, 2024-12) Kaplan, Louisa; Carey, AnneRiverine carbon transport is a key component of the global carbon cycle, and it is important to understand how human activities like urbanization, agriculture, and damming affect the movement of carbon through a river system. The Scioto River, which flows through central Ohio, offers a valuable opportunity to study anthropogenic effects on the transport of particulate organic carbon (POC) because it passes through both agricultural and urban areas, and has two reservoirs. The Scioto was sampled nearly monthly for one year at four different locations along a transect from predominantly agricultural to urban land use areas. POC concentrations at each location were analyzed for patterns in relation to seasonal variability and percentage agricultural land cover of the drainage area. POC concentration was not correlated with the proportion of agricultural land use, but land use types showed distinct responses to similar environmental conditions, such as drought. Our findings matched some predicted patterns, such as the influence of discharge and seasonality on POC, but the effects of the reservoirs were unexpected. These results highlight the importance of future work on the complex interactions between human activities and riverine POC transport.Item The Use of Diatoms as a Proxy for Environmental Variation in Ohio's Inland Lakes(The Ohio State University, 2024-05) Shirk, Trinity; Leonard-Pingel, JillGlobally, lacustrine environments are negatively impacted by anthropogenic nutrient input. In Ohio, many inland lakes have been particularly impacted via agricultural runoff. Determining past water quality and nutrient levels in nutrient-enriched lakes can help inform lake restoration efforts seeking to alleviate the negative effects of nutrient enrichment by providing valuable baseline data. Diatoms, photosynthetic microalgae, can serve as indicators of aquatic ecosystems' health. This project employs diatoms as a proxy for nutrient (e.g., phosphorus) enrichment in seven lakes in the Eastern Corn Belt Plains ecoregion of Ohio, focusing on diatom relative abundances (RAs) to understand which taxa are associated with nutrient-enriched waters. Using this proxy to better understand changes in nutrient concentration in Ohio’s lakes can help us understand how and why aquatic systems change throughout time because, while understanding modern water quality is important, establishing water quality baselines is necessary for effective restoration. This data will serve as the framework for the creation of a statistical model that will be employed to reconstruct total phosphorus concentrations in one of Ohio’s oldest reservoirs, Buckeye Lake. The results of this study will be shared with environmental agencies and local community organizations to help inform future restoration projects.Item CALCIUM ISOTOPIC ANALYSIS OF WATER SAMPLES ON SAN SALVADOR ISLAND, THE BAHAMAS(The Ohio State University, 2024-05) Kachmar, Nolan; Griffith, ElizabethWater chemistry of lakes and ponds on San Salvador Island in The Bahamas are influenced by the geological make-up of the island as well as seawater intrusions and the presence of conduits connecting the surface waters to seawater. Evaporation rates are also important for lakes and ponds in The Bahamas. The chemistry of water samples collected on the island were compared to their calcium isotopic composition (δ44/40Ca) to determine how similar the water bodies are to seawater. Seven different water samples were collected and analyzed for δ44/40Ca and elemental concentrations of calcium (Ca), magnesium (Mg), and strontium (Sr). The δ44/40Ca values and elemental concentrations (Ca, Mg, and Sr) were used to determine factors that may affect water chemistry such as evaporation, sea spray, presence of a conduit (connection to the ocean), and carbonate rock dissolution by freshwater infiltration. From my results, all samples excluding Inkwell Blue Hole, Salt Pond and the shallow groundwater sample from the Gerace Research Centre (GRC) well, look similar to seawater based on δ44/40Ca compositions. Inkwell Blue Hole and the GRC well both had δ44/40Ca values that were lower than seawater and resembled carbonate rocks. The hypersaline Salt Pond had high concentration of Ca but a lower δ44/40Ca than seawater suggesting that the water chemistry may be influenced by other processes such as elevated evaporation rates and carbonate rock dissolution or mineral precipitation.Item Searching for the 1867 Tsunami in the Greater and Lesser Antilles Islands(The Ohio State University, 2024-05) Schmetzer, Nicholas; Sawyer, DerekThe Greater and Lesser Antilles form a chain of islands in the Caribbean Sea which lie on an active plate margin. This area is known for experiencing devastating hurricanes, earthquakes, and tsunamigenic events. Earthquakes and tsunamis are important natural disasters to study because of their destruction to coastal areas and to those who live in those areas. Earthquakes and subsequently tsunamis create extensive damage to infrastructure, landscapes, ecosystems, and amass countless casualties. Studying tsunamis and understanding how and why they form, allows us to prepare better for the future by setting up risk assessment protocols in the event they should occur. Retrieving sediment cores from undisturbed areas affected by tsunamis allows us to analyze the sediment deposition and observe any disruptions without disturbances from living organisms. Coastal salt ponds make excellent traps for tsunamiites, due to their high salinity and lack of life within the ponds. Tsunamiites are sections of the sediment record which are noted by disrupted sediment deposition, preserving evidence of a tsunami inundation events. Outlined in this paper are the steps taken to discover salt ponds and decide systematically which salt ponds are the likeliest to contain tsunami deposits. Further studies of higher ranked salt ponds may find evidence of this tsunamigenic event, which will further assist in understanding tsunami frequency and to plan better for the futureItem Developing Algorithms to Infer Mineralogy of Particles in Taylor Glacier Ice Cores from Elemental Composition Data Measured by spICP-TOFMS and TEM-EDXS(The Ohio State University, 2024-05) Smith, Andrew; Olesik, JohnThe mineralogy of atmospheric particles affects the amount of light scattered and absorbed by these particles as they pass through the atmosphere. A classification system described in this thesis was developed to automatically infer mineralogy of particles based on their measured elemental chemical composition and the elemental chemical composition of known minerals. When comparing the particle's elemental composition to preset ranges for each mineral, if a particle falls within that range, it is marked as elementally similar to that mineral. When each ratio is converted to python code and applied to elemental composition output files, each particle can be labeled as any chemically similar mineral. The elemental chemical composition of hundreds of thousands to millions of particles atmospheric particles entrapped in glacial ice samples can be measured using single particle Inductively Coupled Plasma-Time of Flight Mass Spectrometry (spICP-TOFMS) in about 2 hours (consuming only about 4 mL of melted ice). A spICP-TOFMS can measure the total number of particles per mL, elemental composition of each particle, and the particle size (mass equivalent diameter). This system of inferring mineralogy was assessed by comparison to Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy (TEM-EDXS) analysis of a limited (50) number of particles from Taylor Glacier samples with manual inference of mineralogy. The system described in this thesis was also used to infer mineralogy of mineral standards whose elemental composition was measured using spICP-TOFMS. After comparisons to multiple methods of inferring mineralogy, the system within this thesis was used to analyze samples of Taylor glacier measured by spICP-TOFMS.Item VARIATION IN NOBLE GAS ISOTOPES FROM VOLCÁN PACAYA SINCE 1961(The Ohio State University, 2024-05) Stalla, John; Barton, MichaelVolcán de Pacaya is a volcanic complex that lies within the Central American Volcano Arc, formed by the subduction of the Cocos plate beneath the Caribbean Plate. In 1961, it began erupting following a 76-year dormancy. The dominant lithology of the lavas erupted during this time has been olivine-bearing basalt. Noble gas isotope ratios can provide chemical signatures for the source of magma, whether it be a subducting plate causing flux melting or mantle upwelling and decompression melting caused by crustal thinning. The 3He/4He ratio from this study indicated that mantle input has been occurring into Pacaya’s magma system since at least 1961. Helium isotope signatures of back-arc volcanism and midocean ridge basalts occur within these lavas. The argon isotopes indicate that the magma has been enriched with mantle material and that the magma did not fractionate before eruption. Lastly, the neon isotopes indicate that some crustal material is present within Pacaya’s magma, but it is dominated by a mantle signal.Item Coupling GIPL Permafrost and Plant Hydraulics Model to Estimate Ecohydrological Responses to Climate Warming in Boreal Forests(The Ohio State University, 2024-05) McNeal, Briana; Liu, YanlanIn Arctic and Sub-Arctic regions, the existence of permafrost, a layer of soil below the earth’s surface that stays below the freezing point of 0°C for two consecutive years, depends largely on air surface temperatures. Therefore, with the occurrence of climate warming, permafrost extent and depth is changing throughout vulnerable regions located within and near the Arctic. With these regions heating up at more than twice the speed of the global average, it is becoming increasingly important to understand the dynamics of permafrost thaw and freeze cycles, as active layer thickness (ALT), which is defined as the height of the subsurface layer that freezes and thaws above the permafrost on an annual basis, affects infrastructure, methane, and carbon emissions. The vegetation that exists in permafrost regions is expected to play a large role in the progression of permafrost degradation, as plant hydraulics interact with the soil moisture, affecting characteristics such as thermal conductivity. Here, we analyze these predicted interactions between plant hydraulics and permafrost depth by coupling the GIPL soil temperature model and a plant hydraulics model. Using a robust soil, atmospheric, and plant hydraulic dataset collected at a site near Fairbanks, Alaska, independent and coupled real-world scenarios were tested. With plant hydraulics, we find that frozen soil depth has an impact on plant water stress. For frozen soil depth, we find that soil moisture impacts soil temperatures. However, sensitivity tests suggest that the thermo-physical properties of organic soils are not accurately captured by the GIPL model without further calibration.Item Reconstruction of Coral Reef Ecosystem Health in Lagoon Cay, Belize Using Invertebrate Assemblages in a Reef Matrix Core(The Ohio State University, 2024-05) Manross, Miranda; Leonard-Pingel, JillCoral abundance is declining worldwide due to anthropogenic factors such as overfishing, agricultural advancements, and human driven climate change. While we have abundant data on reef coverage from underwater surveys completed in recent decades, there remains significant gaps in reef ecosystem data predating the 1970s. Reef matrix cores can help fill this knowledge gap by providing long-term records of reef community change prior to global-scale anthropogenic disturbance. We analyzed subfossil invertebrate assemblages preserved in lagoonal reef-matrix cores from Lagoon Cay, Belize. Bivalves, gastropods, coral, and echinoderm spines were sorted from sieve residue at 5-cm increments. Bivalves and gastropods were identified and counted. Echinoderm spines and coral were identified and weighed to obtain proportional abundance. All were identified to the lowest taxonomic level, typically to genus. Observed in this core is pre-colonial stability amongst the represented taxa. These stability patterns signal the abundance of available hard substrate (i.e., reef building corals). Herbivorous gastropods dominated the gastropod assemblage throughout the core, which is likely due to the abundance of benthic algae accessible to graze on over hard substrate. Despite its role as a keystone herbivore within Caribbean reefs, Diadema antillarum was not the dominant urchin anywhere in the core. Instead, Echinometra spp., the dominant urchin on these reefs today, was the most abundant urchin in all sections. The trends in available taxa show a healthy reef in the represented time. This contrasts other Caribbean cores as well as other cores from Belize. This could be due to the core not extending far enough into the present with the most recent date being 1867. Investigating long-term changes in coral reef invertebrate communities can reveal the ecosystem-level effects of recent declines in Caribbean reef-building corals.Item A Physical Analysis of Icelandic Lavas: What Clinopyroxenes Reveal About the Southwest Reykjanes Peninsula(The Ohio State University, 2024-05) Wiksell, Cameron; Barton, MichaelThe geology of Iceland’s Southwest Reykjanes Peninsula is unique and not fully understood, and volcanic activity persists into modern times. It is a special location where a plate boundary is pulling apart, creating rift volcanism. To get a better foothold in understanding this complex geology, petrographic analyses were performed. Samples were collected from areas of high volcanism, namely Midfell, Litla Sandfell, and to a lesser degree Fagradalsfjall, Geitafell, and the southwestern tip of the Reykjanes Peninsula. Most of these samples were basaltic lavas or glasses erupted from nearby volcanic features. Detailed visual analyses were conducted on thin sections made from these igneous samples. Mineral makeup and volcanic textures present in these minerals were documented. Clinopyroxenes were studied in more detail, due to their common occurrence and ideal textures such as zoning that can tell a lot about magmatic processes. Due to the distribution of clinopyroxenes at these locations, Midfell and Sandfell were able to be analyzed in more depth than the other three localities.Item Mineralogical Analysis and Material Source Interpretation of a Gravity Core from Marsili Seamount (Tyrrhenian Sea)(The Ohio State University, 2024-05) Bzdafka, Jacob; Sawyer , DerekMarsili Seamount (MS) is the largest volcano in the Mediterranean Sea with a peak at about 3000 m above the seafloor and -500 m below sea level. MS has been labeled as a potential geohazard due to measured 3He/4He anomalies indicating gases are being released by an active magma chamber. The core location is 328 m below the summit and possibly provides a view of the recent activity of MS. Physical characteristics data was collected from the core by a multi sensor core logger (MSCL) and grain size data was acquired via laser diffraction (LD). Smear slides were created, and XRD data was collected from the samples analyzed in this paper. The gravity core is comprised of a 13 cm clayed silt upper zone and a lower 25 cm thick volcanic zone made of lapilli and ash tephra layers. This volcanic zone is composed of high amounts of glass implying the source is that of an underwater eruption and it can be described as a tephra bearing unit. Additionally, plagioclase, muscovite, and augite are major minerals in the lower zone and further imply an igneous source. The loose nature of the volcanic zone, as well as its moderate grain sorting and an irregular upper contact, are consistent with near-source flows. These characteristics are similar to those of other cores taken from MS. However, without additional chemical composition data, it is difficult to confidently determine an exact source for the volcanic material.Item Investigation of Cobble Bar Morphology and Sediment Texture in an Arctic River(The Ohio State University, 2024-05) Shoen, Kyle; Sawyer, AudreyDifferent methods are widely used to map grain size distributions in rivers, and a comparison of these methods could give better insight into the fluvial geomorphology of Arctic rivers, which are inaccessible to sampling over much of the year. This study focuses on the Miella River near Abisko, Sweden (latitude 68N), which has ice break-up and flood events. I analyze grain size across six geomorphic zones that were identified along a characteristic cobble bar and adjacent riverbed. As part of this analysis, I compare manual Wolman pebble counts and ground-based photographic analysis of sediment textures. Ten evenly scattered ground-based photographs from each of the six zones were taken approximately 1 m from the surface level and were analyzed using BASEGRAIN, an automatic MATLAB-based object detection software. BASEGRAIN was rapid to implement compared to Wolman pebble counts but challenging to implement in submerged portions of the channel, leading to inaccuracies in grain size estimation underwater. Both BASEGRAIN and Wolman pebble counts identified distinct sediment texture differences between zones. This study contributes to a larger effort to shed new light on geomorphologic and sediment transport processes of the Miella River and will help guide the selection of different grain size analysis techniques in future Arctic river studies.Item How Does Radar Interact with Forests: Quantifying Forest Impact on Snow Radar Remote Sensing(The Ohio State University, 2024-05) Boeing, Felix; Durand, MichaelSnowpack stores winter precipitation allowing for sufficient streamflow to meet spring and summer demand. Snow is an essential water source and supplies water for drinking and irrigation throughout the year. Climate change has been impacting and will continue to impact snowpack which will have far reaching consequences for food, water, and energy security, the economy, human health, biodiversity, wildfires, and climate change itself. It is more important now than ever to understand snow extent, snow properties such as depth and snow-water equivalent (SWE), and snowmelt dynamics. Despite the need for this data, snow remote sensing is not yet in a place where the questions of how snow might melt and how much water is contained within the snow can be answered. The best idea is a dual frequency dual polarization synthetic aperture radar and radiometer (SWESARR) at X and Ku band frequency to maximize sensitivity to various snow and vegetation properties. SWE calculation is especially difficult in forested area with a biomass density of greater than 100 m3/ha or a cover fraction (Cf) of greater than 30%. Most studies look at the volume scattering extinction of radar by canopies and use radiative transfer models where SWESARR readings are insufficient but neglect signal enhancement before the trees. We examine both enhancement and extinction in forested areas and propose a conceptual model against which to compare our results. We find a geometric enhancement of about 4 dB, an extinction magnitude of around -16 dB, with enhancement occurring at a distance of half the height of the trees and a signal recovery occurring at a distance of two thirds the height of the trees. Algorithms should consider both extinction and enhancement when estimating SWE to maximize accuracy.Item Strain Partitioning around Faults in the Lake District of the Southern Andes(The Ohio State University, 2024-05) Kras, Peter; Griffith, W. AshleyThis study addresses the variation of principal strains throughout the Southern Andean Volcanic Zone (SVZ). The SVZ has two prominent fault structures known as the Liquiñe-Ofqui Fault System (LOFS) and Andean Transverse Faults (ATF). The LOFS is a major transverse fault structure that strikes parallel to the margin and the ATF are crustal scale faults that strike NW and NE. Both fault structures are seismically active, underly many of the volcanic edifices in the SVZ, and partition strain from the obliquely convergent margin. To understand the strain partitioning throughout the region, kinematic information like slip direction and slip sense of brittle fractures were collected at various localities. The analyses of the fractures were run as fault-slip data inversions at the local and regional scale. The regional scale strain analysis displayed kinematically heterogeneous faulting with the predominate dextral strike-slip NE-striking faults of the LOFS. The local scale strain analysis displayed either homogeneous or heterogeneous results based on the individual locality. I discuss the calculated principal strain directions for each locality in the context of the local fault structure. Principal strain orientations vary considerably from locality to locality and deviate from the regional strain tensor. This can be interpreted in terms of strong strain partitioning throughout the SVZ due to mechanical interactions between the LOFS and ATF.Item Analysis of Bottom Simulating Reflections in the Blake Ridge 2D Seismic Reflection Data(The Ohio State University, 2024-05) Krysova, Anastasiia; Cook, AnnDuring the summer of 2023 I participated in a 2D seismic cruise on Blake Ridge. In this thesis, I analyze seismic reflection Lines 1001 and 1003 that were processed during the cruise. My interpretation is focused on identifying evidence for natural gas hydrate in near seafloor sediments. Gas hydrate is an ice-like substance that contains a highly concentrated source of methane. In seismic data, I look for and map bottom simulating reflections, which serve as indicators for the presence of gas hydrate. These reflections appear at the bottom of the gas hydrate stability zone. Line 1001 contains a clear, continuous BSR. Using the TgradBSR, an application that estimates the depth of the BSR, I calculated the thermodynamic base of gas hydrate stability. This requires pressure, salinity, seafloor temperature data, and the geothermal gradient. Using two different geothermal gradients from Ocean Drilling Program Leg 164, Site 994 and 995, two estimates of the BSR depth were calculated. The observed BSR depth was shallower than the two estimates. The change in the seafloor temperature and the P-wave velocities may have affected the depth of the BSR to some extent, but the greatest factor affecting the depth of the BSR was the geothermal gradient. Using a higher geothermal gradient of 39.6 °C/km, compared to Sites 994 and 995, the estimated BSR depth matches the observed BSR depth.Item INTERPRETATION OF WHOLE-ROCK GEOCHEMICAL DATA OF VOLCÁN DE PACAYA, GUATEMALA 2008-2021 LAVA FLOWS(The Ohio State University, 2024-05) Nidy, Claire; Barton, MichaelThe Pacaya Volcanic Complex in Guatemala sits atop an active subduction zone. With the Cocos plate (sitting below the Pacific Plate) moving to the east and subducting under the Caribbean plate, active volcanism presents itself about 40 miles inland into Guatemala and surrounding Central American countries. Yet, this volcanism has a geochemical signature of back-arc basin volcanism rather than arc magmatism, as would be expected of this tectonic boundary as seen in other subduction zones around the world. From 17 samples of Pacaya lava flows dating from 2008-2021, 10 major oxides and 18 trace elements have been accounted for and analyzed. This data gives the necessary geochemical information to interpret the type of volcanism occurring within the complex. Additionally, the data gives vital information as to the state of the magma chamber and melt composition or the Pacaya complex over this 2008- 2021 time.