Ph.D. - Earth and Planetary Sciences

Permanent URI for this collectionhttps://hdl.handle.net/10125/63099

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From laboratory to launch: Infrared instrument development and informing ISRU strategies on the Moon
(University of Hawai'i at Manoa, 2025) Ferrari-Wong, Chiara; Lucey, Paul G.; Earth and Planetary Sciences
This dissertation presents a comprehensive approach to developing infrared instruments, from fundamental calibration to space-based implementation, complemented by lunar methane sequestration modeling to inform ISRU (In-Situ Resource Utilization) strategies for future missions. The second chapter establishes methods for infrared camera calibration, examining key performance characteristics and predictive frameworks that will help us characterize the behavior of these types of instrument systems. Utilizing these calibration techniques, the third chapter details the development of the Hyperspectral Thermal Imager (HyTI), an Earth observation instrument developed at the University of Hawai'i at Mānoa through collaboration between the Hawai'i Spaceflight Laboratory (HSFL), the Hawai'i Institute of Geophysics and Planetology (HIGP), and the Jet Propulsion Laboratory (JPL). The optical design process and my performance model, driven by mission requirements, enabled the instrument to achieve 20 spectral bands between 8 and 10.7 μm with a 60-meter ground resolution. The calibration methods from my second chapter provided key detector metrics, including bias, gain, read noise, and dark current for this instrument. Validation of my performance model's accuracy during development establishes a framework for future HyTI-like instruments that can be adapted for other scientific applications. The fourth chapter focuses on the end product and motivation of instrument design and calibration: science; specifically, modeling adsorbed methane sequestration in permanently shadowed regions on the Moon. This chapter finds that up to 70 μg/g of methane can be sequestered in the upper meter of regolith over geological timescales, providing critical insights for ISRU strategies and supporting missions such as Artemis III and VIPER.
Some aspects of the chemistry and volcanology of hotspot volcanoes: From seamounts to ocean islands
(University of Hawai'i at Manoa, 2025) Gauer Pasqualon, Natalia; Pietruszka, Aaron; Earth and Planetary Sciences
The products of hotspot volcanoes vary widely in composition, eruptive style, volume, and emplacement conditions, and a great diversity of tools is required to unravel their origin and evolution. This dissertation investigates hotspot volcanoes and other features of oceanic intraplate volcanism on the Pacific plate, by applying geochemistry, stratigraphy, and video analysis across four independent projects. Chapter 2 examines the chemistry of the Cretaceous Naifeh-Plumeria seamount chains, revealing FOZO-like isotopic signatures in the upper mantle, suggesting their formation through small-scale convection rather than classic plume activity. Chapter 3 investigates the Cretaceous Wake seamounts in the West Pacific Seamount Province, identifying two isotopically distinct groups: one linked to the long-lived Rurutu-Arago hotspot and the other to shallower, plume-unrelated mantle sources, providing constraints for reconstructing Pacific plate motion prior to 80 Ma. Chapter 4 provides new insights into the eruptive history and hazards of rejuvenated volcanism on Oʻahu, Hawaiʻi, through a detailed stratigraphic study of the Koko Rift System (~67 ka). Chapter 5 introduces webcam videography for quantifying eruption parameters, applied to the 2022 Mauna Loa summit lava fountaining. By tracking fissure growth, lava fountain heights, and eruption flux rates through webcam footage, this study establishes a cost-effective tool for monitoring eruptions in near-real time. In summary, the study of chemical and physical properties of hotspot volcanoes conducted in this work provides a better understanding of the broader interplay of deep mantle structures and mantle convection, surface processes and eruption dynamics.
Characterizing olivine-carbonate rocks on Mars with rover datasets and numerical modeling
(University of Hawai'i at Manoa, 2025) Ravanis, Eleni; Fagents, Sarah; Earth and Planetary Sciences
The Perseverance rover landed in Jezero crater in 2021, in an area of Mars rich in olivine- and carbonate-bearing rocks. Olivine-rich rocks on Mars are of interest for understanding magmatic and igneous processes, in addition to the extent of past surface water, given that olivine is readily altered by water on geologic timescales. Carbonate-rich rocks are also a key target for exploration on Mars given that carbonate typically requires water to form, and has high biosignature preservation potential. Therefore, this dissertation was motivated by a desire to understand the origin of these rocks and to provide context to the Perseverance rover’s exploration of Jezero crater. In Chapter 2 I use numerical modeling to investigate the settling of ash particles from mafic explosive volcanic eruptions on Mars, and to assess the plausibility of a pyroclastic origin previously proposed for the Nili Fossae olivine-carbonate unit based on analyses of orbital data. My results show that ash from pyroclastic fall eruptions was likely less widely dispersed than previously proposed on Mars. Additionally, my results also show that if the Nili Fossae olivine-carbonate unit originated as a primary pyroclastic fall deposit, then multiple, currently unidentified sources, potentially combined with a higher-pressure atmosphere, are needed to account for the unit’s spatial extent. In Chapter 3, I use Perseverance Mastcam-Z red-green-blue (RGB) and multispectral images to examine the formation and alteration of olivine- and carbonate-bearing rocks within Jezero crater, and their potential relation to the regional olivine-carbonate unit. My results demonstrate that olivine-rich rocks on the crater floor known as the Séítah formation and previously interpreted to be layered cumulates, are distinct from the olivine- and carbonate-rich rocks of the Margin unit, but may share a genetic link, and that the extent of carbonate formation may be related to the presence of the Jezero paleolake. In Chapter 4, I use a combination of Mastcam-Z RGB and multispectral images, as well as SuperCam Remote-Micro-Imager images and visible-infrared spectra, to characterize olivine-bearing rocks across the Jezero crater rim and discuss their formation and alteration history. My findings show that these rocks may have originated as igneous intrusions or lava flows, and that olivine-bearing rocks on the crater rim experienced a distinct alteration history dominated by phyllosilicate formation, in contrast to the carbonated rocks found below proposed past stable lake levels within the crater. The results taken together suggest that intrusive igneous rather than pyroclastic processes played an important role in the formation of rocks within the Jezero crater region of Mars.
Magma storage, evolution, and mixing within Kīlauea volcano’s lower east rift zone
(University of Hawai'i at Manoa, 2025) Gallo, Rose Isabelle; Shea, Thomas; Earth and Planetary Sciences
Kīlauea volcano is well known for its frequent effusive eruptions both within the summit caldera and on its flanks along two rift zones. Recent activity within the East Rift Zone, the more active of the two, has damaged and destroyed communities located on the more distal portion of the rift, referred to as the Lower East Rift Zone. A pattern of rift zone eruptions beginning with cooler, more evolved lavas and then transitioning to more mafic compositions over time has been recognized at Kīlauea. The evolved lavas are derived from pockets of magma stored within the rift zone that differentiate in isolation between eruptions and are then remobilized by new intrusions. The eruption that occurred in the Lower East Rift Zone in 2018 involved the remobilization of two different evolved lavas: a differentiated basalt at the beginning of the eruption and then an andesite thirteen days later along a separate fissure line. The first chapter of this dissertation provides background on Hawaiian volcanism and the history of the Lower East Rift Zone. The second chapter focuses on the andesite, and mafic enclaves that were found within it. We analyzed the textural and geochemical properties of the enclaves and host lavas and compared them to other historical lavas from the Lower East Rift Zone to determine the source of the enclaves. We concluded that the source was the basalt that simultaneously mixed to form homogenous basaltic-andesite at other portions of the same fissure and erupted contemporaneously from adjacent fissures. We developed a computational model for enclave thermal equilibration within the andesite to explain how the preservation of enclaves and homogenization of the same two magmas could occur along the same fissure as a result of locally varying mixing percentages of the andesite and basalt. Chapter 3 focuses on the differentiated basalt erupted at the beginning of the 2018 eruption. We used whole rock, mineral, and glass major and trace element compositions to evaluate a potential source for this magma and concluded that it was most likely a remnant of the magma involved in the beginning of the 1955 eruption. The small compositional difference between the connected magmas was used to suggest a slow cooling rate for the magma body of roughly ~0.1 °C/year. Chapter 4 considers a magma that did not erupt in the Lower East Rift Zone and instead was encountered in the subsurface during geothermal drilling. This magma, a rhyolite, is the most evolved material ever sampled at Kīlauea, and its discovery was the first instance of a melt being encountered during drilling. We characterize the petrography and geochemistry of this sample and consider the possible origins of the magma. This unique sample, collected at a precisely known depth, is utilized to perform a spot-check on the accuracy of petrologic tools used to estimate magma storage pressures and the models for temperature and water content they depend on. Chapter 5 provides a summary of the broader conclusions of this work and some suggestions for future avenues of investigation. The work described in this dissertation contributes to an enhanced understanding of processes during magma storage and magma mixing within Kīlauea’s rift zones and to a broader discussion of how to leverage the best tools for making interpretations about the origins of magmas and pre-eruptive storage conditions.
Craters, cryovolcanism, and clathrates: Exploring interactions between titan’s ice shell, surface, and atmosphere
(University of Hawai'i at Manoa, 2025) Brouwer, Gwendolyn Elaine; Fagents, Sarah; Earth and Planetary Sciences
Titan’s subsurface liquid water ocean and organic-rich surface and atmosphere make it a particularly exciting target of interest for astrobiology. Its dense atmosphere requires a methane replenishment mechanism, potentially linking the interior and atmosphere. Interactions between the interior, surface, and atmosphere manifest in various geologic features, such as modified impact craters and potential cryovolcanic features, indicating that Titan is a dynamic world. This dissertation explores the interactions between Titan’s ice shell, surface, and atmosphere through three distinct projects. Chapter 2 focusses on the formation of Titan’s rampart craters, investigating an endogenic origin through a gas explosion mechanism. This project models the explosive release of gas from liquid methane and nitrogen, and gas sourced from methane clathrate. I find that an explosive origin for rampart craters can reproduce the observed morphologies, estimate the amount of gas released into the atmosphere, and discuss the implications for atmosphere replenishment. Chapter 3 examines the potential for effusive cryovolcanism via a pressure-driven eruption mechanism for transporting subsurface materials to Titan’s surface. I constrain the conditions under which pressure-driven eruption are feasible and the characteristics of the resulting cryolava flows. Chapter 4 investigates the role of a clathrate crust in the topographic relaxation of complex impact craters on Titan. By comparing the simulated crater morphologies to observed craters on Titan, we provide constraints on the thickness of Titan’s clathrate crust. Overall, this dissertation advances our understanding of the dynamic processes shaping Titan’s surface and subsurface, including potential cryovolcanic mechanisms and impact crater formation and evolution.
Acoustic explosion and rocket signatures from surface and airborne smartphones
(University of Hawai'i at Manoa, 2025) Popenhagen, Sarah Kathleen; Garcés, Milton A.; Earth and Planetary Sciences
Rocket launches produce complex acoustic signatures with large amounts of energy in low (<300 Hz) and infrasonic (<20 Hz) frequency ranges. These acoustic signatures carry information about their source as they propagate through the atmosphere, which, if correctly detected and classified, can aid in monitoring efforts. Many infrasonic rocket signatures have been successfully collected after propagating great distances (>1000 km), but most of these signatures are highly attenuated, yielding broad insight but little detail into the nature of the launch that produced them. In addition, very few of these data are available to the public, limiting the rate of progress in the field of rocket acoustics.The overarching goal of the work covered in this dissertation is to develop a fast and reliable method of detecting acoustic rocket launch signatures. Results from each of the three content chapters contribute towards this goal. In Chapter 2, a surface chemical explosion signal is observed from an ascending balloon in the middle stratosphere. From this case of a stationary surface source and an ascending airborne receiver, we can gain insight into the inverse case of an ascending airborne source (a rocket) and a stationary surface receiver by invoking reciprocity. In addition, a comparison of low-cost, low-maintenance sensors (smartphones) with traditional infrasound sensors is made. In Chapter 3, a dataset of acoustic rocket signatures collected on smartphones at estimated propagation distances of 10-70 km is presented and released to the public, accompanied by preliminary analysis of the chronology and time-frequency characteristics observed in the dataset. In Chapter 4, this dataset is used in concert with two other open-access datasets to train and test machine learning models for near-real-time detection of acoustic rocket launch signatures on mobile platforms. The best performing model showed promising results, with an overall accuracy of 97% and a false positive rate of <1%. Measures to improve the model’s suitability for persistent monitoring are discussed, implemented, and evaluated, resulting in an estimated effective true positive rate of 99% and false positive rate of 0.07%.
Remote Sensing Investigations of Lunar Surface Evolution
(University of Hawai'i at Manoa, 2024) Chertok, Marley Aviva; Lucey, Paul G.; Earth and Planetary Sciences
The lunar regolith, a poorly sorted layer of impact-generated debris that coats the entirety of the lunar surface, underlies the boots of astronauts, composes a large portion of the lunar sample suite, and is the primary material scientists can study remotely. Therefore, understanding the nature and evolution of regolith is essential to planning future missions. This dissertation explores differences in rock and regolith evolution on diverse surfaces across the Moon using multispectral remote sensing data and impact craters. In Chapter 2, I demonstrate that the volcanic maria, which were once thought to be homogeneous, are diverse and were likely formed by a spectrum of emplacement conditions. Thus, the regolith on these diverse surfaces evolves variably depending on the properties of the parent rock. In Chapter 3, I show that the highlands, which cover most of the lunar surface, are blanketed by a thick regolith that is highly variable. The estimate of a 10-15 meter thick regolith at the Apollo landing sites has typically been taken to be representative of most of the highlands. However, my analysis of rocky craters reveals that 95% of the highlands are covered by regolith thicker than 50 meters. Finally, in Chapter 4, I show that highlands topography influences regolith maturity. Relatively immature regolith is more likely to occur atop high-standing topography, while mature regolith is more common on low-lying terrain. This is a key finding that is relevant to the upcoming Artemis missions, which will explore high topography at the lunar South Pole. My findings enable us to predict that Artemis astronauts will encounter regolith that is immature and possibly abnormally thin due to the catastrophic loss of material from topographic highs.
The spatiotemporal evolution of severe droughts in coupled global climate models: drivers and impacts in the past and future
(University of Hawai'i at Manoa, 2024) Ellison, Lucas Macrae; Coats, Sloan; Earth and Planetary Sciences
Persistent and severe droughts have occurred regularly over the late Holocene, however, few of these events have been directly observed and thus their impacts and drivers are not well understood. To overcome the challenges associated with a short observational record, coupled global climate models have been used to establish that internal modes of atmosphere-ocean variability, intrinsic atmospheric variability, and land-atmosphere feedbacks all play a role in the life cycle of droughts in North America, in addition to external forcing. We build off this prior work, quantifying the full range of large-scale drivers and local-scale impacts of meteorological droughts in climate models, establishing the relative importance of different types of uncertainty for these ranges, and then determining how and why the drivers and impacts of meteorological drought will change in the future under anthropogenic climate change. This dissertation develops a framework through which the spatiotemporal characteristics of simulated meteorological droughts (i.e. precipitation deficits), as well as their drivers and impacts, can be compared to an observed event. The drought in central and western North America between 2011 and 2014 is used for comparison throughout due to its location, severity, and a high availability of observational data. In Chapter 2, we establish the framework, identifying meteorological droughts based on their precipitation deficits and spatiotemporal characteristics. Chapter 3 utilizes this framework to determine the consistency of the local-scale impacts and large-scale drivers of meteorological droughts in 65 coupled global climate model simulations. We found that a range of atmosphere-ocean conditions can lead to droughts with similar spatiotemporal characteristics, and that the precipitation deficits during these droughts can have a range of hydrological and ecological impacts. In Chapter 4, we utilized initial condition large ensembles to quantify the relative roles of intrinsic climate variability and structural uncertainty in the range of atmosphere-ocean conditions from Chapter 3. We find that while both intrinsic variability and structural uncertainty play a role, structural uncertainty is substantially larger. In Chapter 5, we compare the spatiotemporal characteristics, local-scale impacts, and large-scale drivers of historical and future meteorological droughts. We found that increased precipitation will lead to fewer meteorological droughts in the future, however their impacts will become more severe for certain aspects of hydrology and ecology. Additionally, the large-scale atmosphere ocean drivers of meteorological droughts are becoming more consistent in the future, with implications for their predictability.
Next Generation Spectroscopic Techniques and Methods for Planetary Exploration
(University of Hawai'i at Manoa, 2024) Kelly, Evan Micahel; Sharma, Shiv K.; Earth and Planetary Sciences
This dissertation covers the various stages of instrument development for planetary science. The first section introduces key concepts, including Raman spectroscopy, spatial heterodyne Raman spectroscopy (SHRSy), and nuclear magnetic resonance spectroscopy (NMR). The second chapter examines the viability of a monolithic spatial heterodyne Raman spectrometer (mSHRS) for planetary missions by testing its performance, coupled with an intensified charge-coupled device, on several samples relevant to planetary science. The results of these tests are compared with those from other spatial heterodyne Raman spectrometers (SHRS) to evaluate their instrumental properties and effectiveness. The third chapter focuses on how different detectors impact the performance of the mSHRS, specifically looking at signal-to-noise ratios and other key instrumental characteristics. The fourth chapter evaluates the performance of a miniature monolithic spatial heterodyne Raman spectrometer in comparison to the monolithic non-miniaturized version. This chapter also features the first polarization study conducted with an mSHRS. Together, these three chapters aim to develop and refine the instrument's design to optimize its use for planetary science missions. The fifth and final chapter marks the beginning of adapting an instrument used on Earth for potential use in planetary exploration. It evaluates the utility and feasibility of implementing nuclear magnetic resonance (NMR) technology in future planetary missions. This is done by examining Titan lake mixture analogs to make use cases for the types of NMR techniques that are essential to fully and successfully analyze liquid mixtures obtained on planetary exploration missions. The analytical capabilities of NMR are then compared to GC-MS and Raman to emphasize the benefits and utility NMR provides compared to these other techniques.
Experimental Investigations on Elastic Properties of Davemaoite and the Iron Carbide-Water Reactions in the Mantle
(University of Hawai'i at Manoa, 2024) Chao, Keng-Hsien; Chen, Bin; Earth and Planetary Sciences
Geophysics has provided a comprehensive overview of the composition and structure of Earth's interior, revealing a silicate mantle and metallic core. In the mantle, CaSiO3 perovskite (davemaoite) poses a challenge due to its enigmatic nature. Simultaneously, the deep volatile cycle raises controversy, considering the unexpectedly high carbon concentration in the mantle and the unidentified light elements contributing to the core's density deficit. The first project (Chapter 3) delves into the structure and density of Ti-bearing davemaoite. As the third and second most abundant phase in the pyrolytic mantle and subducted mid-ocean ridge basalt, respectively, davemaoite plays a crucial role as a Ti-hosting phase. In Chapter 3, we scrutinized the structure and density of Ti-bearing davemaoite (Ca(Si,Ti)O3) under relevant mantle pressure conditions. Surprisingly, Ti-bearing davemaoite was found to be less dense than its pure CaSiO3 counterpart. Given this lower density, we postulate that Ti-bearing davemaoite could contribute to slab stagnation and the formation of large low shear velocity provinces. The second project (Chapter 4) focuses on reactions between volatile-bearing species in the mantle. By investigating Fe3C-H2O and Fe7C3-H2O using a multi-anvil press at 15-23 GPa, 1000-1600°C, with Mg(OH)2 as a water source, we discovered diamond formation through the iron carbide-water reaction, confirmed by electron microprobe and Raman spectroscopy. We propose that diamonds might have formed and been retained in the silicate portion of Earth if Fe-C alloy droplets interacted with water in the early magma ocean. Furthermore, the iron carbide-water reaction could persist, generating diamonds on the slab's surface in the modern mantle, a factor to consider when calculating specific water quantities delivered to the core through slab subduction. The third project (Chapter 5) explores the direct reaction between iron carbide and water ice at ~20-60 GPa using a laser heating diamond anvil cell. The results indicate diamond formation through a direct reaction between iron carbide and water ice, as confirmed by XRD and Raman spectrometry. This suggests that diamonds can form at various depths whenever iron carbide encounters a water source. However, the data reveal a complex assembly of reaction products primarily due to system disequilibrium, prompting the need for future work with higher heating temperatures and longer durations. In summary, Chapter 3 proposes that Ti-bearing davemaoite may contribute to slab stagnation and the formation of large low-shear velocity provinces. Chapters 4 and 5 unveil that diamonds can form in the mantle when iron carbide encounters water sources, providing new insights into our understanding of the deep volatile cycle.
Elucidating the Role of Titanomagnetite in the Vesiculation of Silicic Magmas from Observations of Natural and Experimental Samples
(University of Hawai'i at Manoa, 2024) McCartney, Kelly Nell; Hammer, Julia E.; Earth and Planetary Sciences
The onset of an eruption is preceded by the nucleation of bubbles in a magma, which in turn reduces its density and increases its buoyancy and compressibility. These factors relate directly the ascent rate of a magma, which controls the style and intensity of an eruption. Therefore, it is critical to understand the mechanism of bubble nucleation, and what factors contribute to the efficiency of vesiculation in silicic magmas. Of particular interest is bubble nucleation in high silica magmas, as the process of bubble nucleation is delayed until the supersaturation of volatiles (e.g., H2O, CO2, and S) occurs. This process requires magma chambers of significant storage depths for bubble nucleation to occur homogeneously (without the aid of a bubble nucleation substrates), or the presence of abundant heterogeneous bubble nucleation substrates for bubble nucleation to occur in magma staged at shallow storage depths. In this dissertation, we first examine pumice and obsidian from the 1060 CE Glass Mountain subplinian eruption and investigate the presence of sub-micron scale heterogenous bubble nucleation substrates (crystals) using applications of magnetic methodologies and physical characterization techniques, as a means to explain how bubble nucleation occurred in an otherwise aphyric (apparent homogeneous nucleation dominated) shallow storage system. We find titanomagnetite in number densities greater than bubble number densities and confirm early titanomagnetite stability in both the pumice and obsidian. Therefore, sub-micron titanomagnetite is present and available to act as a heterogeneous bubble nucleation site in this system. We extend our application of rock magnetic methodologies and physical characterization techniques to aphyric pumice from other rhyolitic eruptions (1912CE Novarupta, 181CE Taupo, and 0.45 Ma Pudahuel) that represent a range of magma storage depths. We also find titanomagnetite in number densities greater than bubble number densities in these systems and confirm early titanomagnetite stability. Sub-micron titanomagnetite may, therefore, act as a heterogeneous bubble nucleation site in magmatic systems where it is abundant and stable, regardless of magma chamber storage depths. From this effort, and observations from past work, we suggest that titanomagnetite is an efficient bubble nucleation site, but the specific effects of increasing titanomagnetite number density on bubble nucleation efficiency are still poorly constrained. So, we conducted a series of 1-atmosphere gas mixing furnace vesiculation experiments to investigate how nucleation of new titanomagnetite crystals affects bubble nucleation efficiency and bubble number density in a natural rhyolite obsidian. Our experimental results confirm that bubble nucleation efficiency is dependent on the nucleation of new titanomagnetite in our experimental samples. The reason for titanomagnetites dominance as a heterogeneous bubble nucleation site has been theorized to be the result of its composition, morphology, and/or its crystal structure. We performed a series of sessile drop experiments involving the melting of rhyolite glass in contact with several mineral substrates, to constrain which of the above factors control the interfacial energy between the solid and liquid phases by observing wetting angles. We find that titanomagnetite is likely the preferred bubble nucleation site due to its composition, morphology, and crystal structure, in addition to its abundant presence and common stability across rhyolitic systems. The work described in this dissertation suggests that heterogeneous bubble nucleation may dominate in previously defined aphyric systems and encourages the use of magnetic analytical methodologies for future investigations into determining bubble nucleation style. In addition, this work provides new insights into the influence of heterogeneous bubble nucleation substrate abundance and composition on bubble nucleation efficiency in high silica systems. Future work should draw from the magnetic analytical and experimental methods described in this dissertation to further our comprehension of bubble nucleation and solidify our understanding of the early stages of volcanic eruptions.
DATA FOR EXPLOSION MONITORING: ACOUSTIC EXPLOSION SIGNATURES COLLECTED ON INFRASOUND MICROPHONES AND SMARTPHONES
(University of Hawai'i at Manoa, 2024) Takazawa, Samuel Kei; Garcés, Milton A.; Earth and Planetary Sciences
Explosions produce pressure waves that consist of low (<300 Hz) and infrasonic (<20 Hz) frequencies that can travel vast distances in the atmosphere. These pressure waves are used to characterize explosions and are monitored through various sensor networks of differing scale and density. Although there is a global network (i.e. International Monitoring System) in place that can monitor large explosions (>1 kiloton), regional and local networks that can monitor small explosions are few and far between due to their cost. Additionally, data from these networks are rarely openly available to the public, making research limited to those with special access, potentially stifling progress.This dissertation introduces acoustic explosion datasets collected on infrasound microphones and smartphone sensors to help address the lack of available data and dense sensor networks for explosion monitoring. In Chapter 2, a chemical high explosive (HE) dataset collected on infrasound sensors is presented. For those who are interested or new to the field, it is accompanied by an overview of acoustic explosion features and standardization methods. In Chapter 3, data from two explosions recorded on an infrasound sensor and smartphone sensor network are presented. The audio data from both sensors are compared, showing how the smartphone microphone filters the waveform due to its frequency response. However, due to the similarities in the frequency and time-frequency domains, as well as data from the additional sensors included in the smartphones, it was concluded that smartphones have the potential to enhance traditional explosion monitoring and identification capabilities. This potential is demonstrated with the introduced source localization method. In Chapter 4, a HE dataset collected on smartphones is presented and used to train machine learning (ML) models to detect explosions. The resulting model showed success in classifying smartphone microphone data as either “explosion,” “ambient,” or “other,” highlighting the potential of smartphones as attritable, ubiquitous sensor networks for explosion monitoring.
Eruption Dynamics of 21st Century Hawaiian and Strombolian Volcanism: Insights from High-Resolution Videography
(University of Hawai'i at Manoa, 2021) Walker, Brett Halsey; Houghton, Bruce F.; Earth and Planetary Sciences
This dissertation focuses on mildly explosive eruptions–the most frequent manifestations of subaerial explosive volcanism on Earth. It uses high-speed and high-resolution cameras to record the erupted particles (pyroclasts) in-flight to measure key parameters on very fine temporal and spatial scales and link them to processes in the shallow conduit. This dissertation is composed of three projects that use data acquired at Kīlauea and Stromboli (two of the world’s most active volcanoes) to investigate what drives rapid changes in the style and intensity of weak (mild) explosive eruptions. This work begins by quantifying the frequency, duration, and steadiness (height fluctuation) of explosive events that generated a spectrum of weak activity (from Strombolian jets to Hawaiian fountains) during the 2018 fissure eruption of Kīlauea (Chapter 2). Footage of pyroclasts falling from the highest and longest fountaining phase of this eruption is then used to quantify processes of secondary fragmentation and expansion. The data show that both of these processes strongly alter the grain size of pyroclasts produced by Hawaiian fountaining eruptions (Chapter 3). On the Strombolian end of the spectrum, a detailed characterization of ejection velocity and grain size is used to interpret the observed pulsations (which occur within single explosions) in terms of the sub-second ordering of gas pockets in the shallowest levels of the conduit. My research, which aims to advance understandings of mild explosive volcanic eruptions, is driven equally by the intense public curiosity about active volcanoes and a pragmatic need to assist in improved forecasting of the likely course and footprint of all future eruptions at Stromboli and Kīlauea.
TECTONIC PROCESSES OF THE PAPUA-WOODLARK-SOLOMON ISLANDS REGION
(University of Hawai'i at Manoa, 2023) Benyshek, Elizabeth; Taylor, Brian; Earth and Planetary Sciences
Globally-significant plate tectonic processes can be observed in detail in the Papua New Guinea – Woodlark Basin – Solomon Islands region. These include the rifting and break-up of a continent and the transition to oceanic seafloor spreading, the initiation and evolution of transform faults, propagating and overlapping spreading centers, the synchronous reorientation and jumping of spreading centers, island arc-plateau collision and the reversal of subduction, and the subduction of topographic rises, seamounts and very young lithosphere. The Woodlark Basin is an ideal location for studying these tectonic processes because it is completely mapped with high-resolution bathymetry, acoustic imagery and magnetic data, in addition to marine and satellite gravity data. A large part of the mapping was completed on R/V Kilo Moana Cruise 0418. Thin sediment covering the basement fabric of the young basin and a clear magnetic reversal history allow tight spatial and temporal constraints to be placed on its tectonic evolution. Most of the tectonic processes are currently active and occurring at high rates (rifting and spreading up to 20 mm/yr and subduction at >100 mm/yr), which allows them to be illuminated by studies of the associated earthquake seismicity over multiple fault rupture cycles. The three-fold increase in the volume and quality of the seismicity data reported post-2010 compared to pre-1995, together with improved procedures for preparing and processing the data, have significantly improved the relocation of catalogued hypocenters, especially their depth. Seafloor spreading in the Woodlark Basin separates the Australia and Woodlark plates and the formerly contiguous eastward extensions of the Papuan Peninsula. To the north, the basin is bounded by the Woodlark Rise rifted margin and the splaying Nubara Transform Fault. The conjugate margin on the south is the Pocklington Rise which, in the east, is bordered to the south by the Itina Trough, a young rift graben. The Woodlark Basin is subdivided at Moresby Transform Fault and Simbo Fracture Zone into the western, eastern and easternmost sections. The westward stair-stepping and propagating of the Woodlark Basin spreading center into the rifting Papuan continent occurred simultaneously with its subduction to the ENE beneath the Solomon Islands. Both occurred post ~8 Ma following the arrival of the 40-km-thick Ontong Java Plateau on the Pacific Plate, whose collision with the Solomon Islands led to a reversal of the subduction polarity, as previously recognized. I present a four-plate kinematic model of present day Woodlark, Australia, Trobriand and Solomon Sea plate motions that reconciles decadal GPS measurements with Brunhes-age seafloor spreading rates and includes subduction of the Solomon Sea Basin at the Trobriand Trough. Euler poles derived from the model are applied to a detailed 100,000-year-interval animation of the formation and evolution of the Woodlark Basin. I propose that the active spreading center being subducted beneath the New Georgia Group of the Solomon Islands comprises the arc-composition volcanoes of Simbo Island and another to its south. The Ranongga Transform Fault that connects this to the Australia-Woodlark spreading centers further west is concave to the east. The formation and rotation of microplates has helped minimize their collision with the Ontong Java Plateau that is still being subducted on the Pacific Plate from the north, as does the slab window shown by tomography and earthquake data to have formed between the conjugate rifted margins that have been subducted. The young Woodlark Basin lithosphere is too weak to sustain plate flexure and form a bathymetric trench yet is strongly coupled to the forearc by arc volcanoes on the subducting crust that nucleate tsunamigenic earthquakes.
An exploration of the origins, evolution, and fate of inorganic chemical constituents in meteoric waters on the island of O'ahu, Hawai'i, USA
(University of Hawai'i at Manoa, 2023) Brennis, Theodore Martin; Lautze, Nicole; Earth and Planetary Sciences
This study examines the inorganic composition of rainfall on Oʻahu, Hawaiʻi, as part of a broader effort to apply natural conservative geochemical tracers to water resource management problems in the State. Pacific Islands grapple with unique water resource challenges due to environmental vulnerability, climate dynamics, and heavy groundwater reliance. Urbanization, population growth, and decreasing rainfall trends also stress Oʻahu's freshwater resources. To address these water resource challenges, understanding the links between meteoric, ground-, and surface waters is crucial. This research consists of three components that use the inorganic chemistry of precipitation to better understand such links. First, we analyzed major ion sources in Oʻahu's rainfall, which revealed that ocean sea spray is the primary dissolved ion source, with perturbations from Asian continental dust, local sediment, and agriculture as dictated by broader weather patterns. Second, we analyzed rainfall stable isotopes (18O and 2H), which indicated that there are distinct geographical, seasonal, and precipitation source-related influences. High-elevation spring sampling also indicated that there are significant fog contributions to groundwater recharge. Finally, we investigated how rainfall chemistry evolves as it infiltrates the soil and present a method to assess changes in the stable isotope composition of precipitation during infiltration. These studies illuminate several key meteorological and physiographic dynamics that affect precipitation chemistry on Oʻahu and provide a baseline from which to assess future fluctuations. They underscore the impact of microclimates and moisture source on the stable isotope composition of precipitation, and highlight the need for topographically diverse, event-based precipitation sampling. Results from the third study highlight the importance of understanding chemical changes to precipitation during the process of infiltration. Cumulatively, these findings lay groundwork for utilizing natural geochemical tracers to understand groundwater flow paths and recharge processes on Oʻahu.
Methods In Image Processing To Improve Understanding Of Laser Induced Fluorescence Response In Moss To Metal And Environmental Stress
(University of Hawaii at Manoa, 2023) Truax, Kelly Lyn; Dulai, Henrietta; Earth and Planetary Sciences
The ability to detect, measure, and locate the source of contaminants or radionuclides is of ongoing interest. There are many techniques for modeling atmospheric transport, sampling near sites of known contamination, and monitoring locations of interest. A widely-used tool for identification and bioremediation comes in the form of vegetation that can serve as indicators of recent and historic events. Large scale vegetation sampling, however, can be costly and labor-intensive, making a non-invasive in-situ technique an attractive alternative. Laser induced fluorescence (LIF) emission is quickly gaining efficacy as a tool to excite biologically-critical molecules, such as chlorophyll, and thereby observe the health of plants and algae. Such techniques are comparable to spectrophotometry, but with the potential benefit of being portable. The technique presented here uses images collected of LIF in moss (Thuidium plicatile) using a CMOS camera to identify the presence of different metals in healthy and impaired tissues. RGB data from each image is recorded and used to create density histograms of each color channel’s relative abundance of pixels where a specific color corresponds to a decimal code value ranging from 0 to 255. Changes in these histograms correlate to shifts in chlorophyll emission and help in the positive identification of very small tissue concentrations at nmol per cm2 levels of copper, zinc, and lead (Cu, Zn, Pb), as well as mixtures of metals. The research focuses on applications of the technique to compare metal contamination to background levels in moss tissues as well as to photoperiod and environmental stressors. Testing included a chlorophyll specific laser system (Semi-conductor diode 445 nm and 462 nm) alongside a Yg:ND pulsed system (355 nm and 532 nm).
Elemental and isotopic compositions of carbonaceous xenoliths in meteorites and of samples returned from comet 81P/Wild 2: an investigation into the diversity of early solar system materials
(University of Hawaii at Manoa, 2023) Frank, David; Huss, Gary R.; Earth and Planetary Sciences
Chondritic meteorites (chondrites) are samples of undifferentiated asteroids, and because chondrites were never melted, they represent fundamental building blocks of the terrestrial planets. Carbonaceous chondrites (CCs) have H and N isotopic compositions similar to Earth’s oceans and atmosphere, respectively, and CCs are therefore a plausible source of Earth’s volatiles. The main components in chondrites are chondrules, which are mm-sized igneous spherules with olivine and/or pyroxene, and fine-grained volatile-bearing matrix. Although chondrules and matrix both formed in the gaseous disk from which the planets formed, the relationship between chondrule formation and matrix is debated, and chondrites on Earth provide us with a limited sampling of the asteroid belt. This dissertation investigates the diversity of chondrules, matrix, and CC materials in the solar system. The first study elucidates the diversity of chondrules with major element, minor element, and O isotopic measurements of olivine and pyroxene returned from comet 81P/Wild 2. The second study investigates the diversity of matrix materials with H and N isotopic measurements of CC xenoliths that were found in meteorites. By comparing our results with chondrites, we conclude that chondrules formed in a limited number of reservoirs and were then widely distributed across the solar system, but matrix materials are more diverse than chondrules, reflecting materials accreted locally, in an asteroid’s feeding zone. A third study examines an unusual halite-bearing CC xenolith in detail. Isotopic measurements constrain the temperature and timing of fluid activity, and point to an origin for this xenolith on a large, cryovolcanically active world.
A Hydrogeochemical Examination Of West Hawaiʻi's Water Cycle
(University of Hawaii at Manoa, 2022) Tachera, Diamond; Lautze, Nicole C.; Earth and Planetary Sciences
Groundwater, sourced from precipitation, is the main source of drinking water in the State of Hawaiʻi. Understanding Hawaiʻi’s groundwater system is critical to understanding future water security. With increasing development, decreasing rainfall, and sea level rise, the uncertainty of Hawaiʻi’s water resource security is a growing concern. The overarching goal of this dissertation is to address the source, flow, and interconnectivity of Hawaiian aquifer systems. This dissertation identified relationships between precipitation and groundwater using stable isotopic compositions of water, flow and connectivity of groundwater aquifers using relative abundances of geochemical parameters, and the relationship between geochemical abundances and spatial distribution. The second chapter evaluates the isotopic and chemical compositions of rainfall from central to leeward Hawaiʻi Island. The study collected cumulative rainfall samples at regular intervals over a 28-month period from 20 stations spanning a range of elevations across this region, and determined average isotopic and dissolved ion compositions in those samples. The study period included an extreme weather event (Hurricane Lane), a major volcanic eruption at Kīlauea in 2018, and the nearly complete cessation of long-term volcanic emissions following that eruptive event. Consistent with previous literature, results show long-term variability through the establishment of an enhanced local meteoric water line (LMWL) for West Hawaiʻi. Additionally, results of stable isotope compositions and bulk ion deposition highlight how extreme events, such as volcanic eruptions and hurricanes, can affect the chemistry of precipitation. The results from this study can be used to better quantify and characterize precipitation, which is the ultimate source of Hawai‘i’s groundwater. Groundwater chemistry studies utilize the occurrence of dissolved ions and other geochemical parameters to determine source, quality, flow, and interconnectivity of aquifers. In groundwater chemistry studies focused on island and coastal environments, a salinity correction is routinely applied, which subtracts the fraction of ocean water from a mixed fresh- and salt- water system in order to focus on fresh-water processes. The third chapter identifies challenges associated with accurate identification of the ocean water fraction in groundwater in a location where dissolved ion contribution can occur through processes that include seawater intrusion, seaspray deposition, wastewater, and hydrothermal reactions. Further exacerbating this challenge is the complex subsurface hydrogeologic environment of West Hawaiʻi Island. The simplistic end-member values for fresh and ocean water currently used in salinity corrections proved challenging for this region. Instead, the study finds the use of end-members chosen from within probable groundwater flow paths produces better results (less frequent over corrections). In addition, this study finds that alkalinity analyses cause higher charge balance errors in groundwater with lower ion concentrations. Charge balance errors may be a good check of quality for datasets, but are not definitive in determining whether a dataset is viable for further geochemical analyses. The fourth chapter uses the geochemical datasets and analyses from previous chapters to better understand areas of recharge as well as the interconnectivity of groundwater aquifers in West Hawaiʻi. The research utilized two methods to calculate groundwater recharge elevations: point-source and fully-integrated recharge. The utilization of two methods constrained the possible range of recharge elevations from Hualālai, Mauna Kea, and Mauna Loa volcanoes. In many cases, the recharge from Hualālai volcano is not isotopically depleted enough to account for the isotopic compositions of groundwater found in the Hualālai aquifer systems. More depleted recharge from Mauna Loa or Mauna Kea volcanoes are additionally needed to account for the isotopically-depleted groundwater. In addition, recharge crosses current aquifer management boundaries used for groundwater resources. The final chapter explores inequalities in funding structures for scientific research. The current academic and research systems are rooted in colonization and continue to perpetuate the exploitation of Indigenous lands and peoples. As the geoscience field works towards a more diverse, equitable, and inclusive environment, leadership from funding agencies must recognize the burden of broader impacts on Indigenous scientists, and the additional devaluing of community engagement and other labor necessary for equitable scientific research practices. Enacting steps for accountability and encouraging best practices in community-driven research are two ways that, as a scientific community, we can raise our standards of ethical research and develop reciprocity and respect, and repair relationships.
Assessment of groundwater age and transport in West Hawaiʻi aquifers
(University of Hawaii at Manoa, 2022) Okuhata, Brytne; El-Kadi, Aly I.; Earth and Planetary Sciences
Groundwater is a freshwater resource that is essential for human existence and supports coastal ecosystems. In Hawai‘i, groundwater provides nearly all domestic water demands and supplements irrigation and industrial needs. As an island state, however, Hawai‘i is completely surrounded by the Pacific Ocean and the fresh groundwater is underlain by saltwater. The groundwater capacity is therefore confined to the boundaries of each island. Additionally, Hawai‘i’s fresh groundwater is susceptible to natural contamination, such as saltwater intrusion caused by over-pumping or sea level rise, as well as anthropogenic contamination sourced, for example, from cesspools, agriculture fields, and urban land development. It is therefore imperative to sustainably manage Hawai‘i’s aquifer systems to ensure these groundwater resources are not depleted. This dissertation examines groundwater flow and transport in the West Hawai‘i aquifers using a combination of groundwater age tracers (CFCs, SF6, 3H/3He, 14C), nutrient tracers (δ15N of NO3-), and numerical models. Sustainable water management requires the understanding of both groundwater quantity and quality, which rely on flow and transport. Apparent groundwater ages help to characterize aquifer storage and groundwater flow properties, which can be combined with nutrient tracers to assess contamination transport. Additionally, numerical models are valuable tools developed to test new conceptual flow models and to assess contaminant transport. The objectives of this dissertation are to 1) estimate the apparent ages of young and old groundwater mixed within the West Hawai‘i aquifers, 2) test a new conceptual model of the area to support the need of groundwater age corrections, and 3) develop a robust groundwater model for the basal Keauhou aquifer to investigate nutrient source and transport. Groundwater age is the time interval between the moment of recharge and the moment of discharge, and is an underlying parameter used for groundwater management. The distribution of apparent ages sheds light on groundwater flow and aquifer storage, which inform groundwater sustainability. Groundwater age can generally be divided into three categories: modern groundwater, old groundwater, and very old groundwater. With proper understanding of aquifer properties, each groundwater age category can be sustainably utilized. Further, groundwater ages can be used to inform how natural and anthropogenic contaminants are transported and dispersed through the aquifer systems. Natural and anthropogenic contaminants are of growing concern in Hawai‘i, where groundwater resources are limited to island areas and vulnerable to environmental changes. Nutrients sourced from on-site sewage disposal systems (OSDS), wastewater treatment plants (WWTP), and urban development can negatively impact groundwater resources and coastal ecosystems that rely on fresh terrestrial water. Groundwater models can therefore be utilized to assess how nutrients are transported through aquifer systems and validate apparent ages. The second chapter of this dissertation estimates the apparent age of young groundwater detected in the West Hawai‘i aquifers using chlorofluorocarbon (CFC), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He) tracers. This multi-tracer approach infers the mixing of young and old groundwater across the West Hawai‘i aquifers. It also suggests that volcanic CO2 influences apparent groundwater ages. The third chapter of this dissertation complements the second chapter by assessing the apparent age of old groundwater from West Hawai‘i using radiocarbon (14C). An isotope mass balance based on δ13C values of dissolved inorganic carbon (DIC) is employed to correct the apparent groundwater ages for the influence of volcanic CO2. Additionally, a two-dimensional groundwater model was developed to support apparent age results using a new conceptual model. The fourth chapter of this dissertation investigates groundwater flow and transport with the development of a three-dimensional density-dependent groundwater model of the basal Keauhou aquifer. The model demonstrates the need of a density-dependent model when investigating coastal aquifers with submarine groundwater discharge. Using δ15N of nitrate (NO3-) measurements, the model estimated the relative contributions of major nutrient sources and tested future scenarios. Findings from this dissertation suggest the mixing of young and old groundwater that are sourced from various distances and elevations. It further demonstrates the complexity of the West Hawai‘i aquifer systems, which requires careful consideration of the subsurface geology and the inclusion of density-dependent flow properties. These findings can be utilized in West Hawai‘i’s groundwater resource management and serve as a catalyst for future work to be done across the state. Further, the methods and implications from this work provide a possible model for studies elsewhere with similar conditions and resource concerns.
Olivine in four dimensions: a textural and chemical record of magmatic phenomena underneath Kīlauea Volcano (Hawai‘i)
(University of Hawaii at Manoa, 2021) Mourey, Adrien; Shea, Thomas; Earth and Planetary Sciences
This dissertation addresses a wide range of research themes centered on understanding how olivinecrystals record magmatic histories. Using experimental, analytical methods, and computational modeling, we assess the textures and chemistry of a set of olivine crystals to answer outstanding yet fundamental questions within the field of petrology and volcanology: (1) How fast are natural olivine phenocrysts formed? (2) How long do olivine crystals preserve the compositional archive of a magma recharge? (3) Can we track long-term changes in the nature of primary melts at Kīlauea with major and trace elements in olivine? The chemical composition of olivine, its zoning patterns (chemical gradients in the crystals) and its textures are commonly used to investigate the evolution of magmas from their source to the Earth’s surface. Compositional zoning in olivine crystals is also a preserved, measurable record that provides constraints on timescales of magma mixing, and transport. This dissertation is composed of four chapters. The first chapter of this dissertation introduces the topics that are involved in the subsequent chapters. The second chapter is a study of the kinetics of olivine growth and the development of characteristic crystal morphologies using laboratory crystallization experiments on a Hawaiian basalt composition. Three-dimensional (3D) characterization is carried out to track the olivine crystallization process in the resulting experiments. A separate set of 3D scans of olivine crystals from an early 19th century Kīlauea eruption yields additional insights into crystal settling and the formation of crystal-rich layers at Kīlauea. In the third chapter, numerical diffusion models that use diffusion chronometry principles are used to determine how olivine phenocrysts preserve their compositional archives and record magmatic intrusions during the 2018 LERZ Kīlauea eruption. The fourth chapter of the dissertation investigates the mechanisms that control the transition from an effusive to an explosive style at Kīlauea using trace elements concentration in olivine. These studies change our perspectives of how olivine crystals should be used to understand the present and past volcanic activity in mafic systems like Kīlauea to better make predictions on future volcanic behavior.

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