The land use in and around Mud Bay, South of Bellingham, has changed over time, including logging, mining and quarrying in the late 1800s to early 1900s, as well as railroad and interstate construction in the 1920s and 1960s. Prior work has shown that the bay is filling with sediment at a rate greater than the projected sea level rise. In this project, we want to document the timing of major land-use change and determine whether the shoreline of the enclosed bay has changed over time. In order to precisely document our data, we georeference historic maps, aerial photographs and satellite images with geographic information system (GIS) software to define the shoreline and map land-use and shoreline changes over the decades. We compare the shoreline and land-use changes correlating with previously extracted sediment cores. With this research, we aim to learn about the competing influences of sea level rise and land-use change on the position of the shoreline and sedimentation in Mud Bay. Conducting this research on Mud Bay will also help us learn how to apply these methods and information to other similar landforms around the world.
 

 Subduction zones are regions where two tectonic plates converge, and one is forced underneath the other. They are the primary driver of plate tectonics, and a source of major earthquakes. These earthquakes occur at shallow depths where plates slide past one another quickly, but at greater depths, with higher pressure and temperature (PT) conditions, rocks behave more ductilely. The transition zone between brittle and ductile regions hosts slow slip events (SSEs), which accommodate motion between the plates during events that last months to years, as opposed to the seconds over which earthquakes occur. SSEs are an important mechanism for accommodating plate motion at depth, thereby affecting the occurrence of larger devastating earthquakes, but currently the processes which facilitate SSEs and the rocks that host SSEs are not well understood. By studying rocks formed in and ancient subduction zone from Santa Catalina Island in California, we can learn more about our own modern counterparts, as the rocks record the conditions where slow slip may have occurred. Using optical petrography and data from x-ray spectroscopy, I examine thin sections of epidote-rich blueschist from SSE PT conditions. Optical petrography allows me to characterize the mineralogy of this rock, and the x-ray data provide the chemical compositions of individual minerals. Using image-analysis software, I will pair these two datasets to estimate the bulk-rock chemical composition of my sample. These data will allow me to constrain the starting material (protolith) of this rock before it was metamorphosed in order to determine if it was originally a sedimentary or basaltic component of the subducting oceanic plate. Doing so will improve our understanding of the way in which rocks at those pressure-temperature conditions deform and chemically change to create the context in which modern SSEs occur.

The Three Sisters Volcanic Complex is located in Lane County, Oregon, and South Sister is considered an active volcano. The USGS observed gradual deformation and uplift around South Sister during 1996-1997. A previous satellite interferometry study of South Sister found that volcanic activity was ongoing during 2020-2021. The results showed that the input rate of magma into the volcano edifice decreased during 2004-2010. Seismic velocity is sensitive to the pressurization state of the system. We can correlate relative seismic velocity with GPS observations to monitor the dynamics of the subsurface of the volcano. The SeisMIC Model is a Python package that provides functionality to apply concepts of seismic interferometry to elastic wave data, reconstructing continuous Green's functions. The expected findings are the relationship between the inflation of the volcano edifice and the seismic velocity change, which could also reveal the relationship between velocity change and deformation. Seismic velocity change is not dependent on the occurrence and location of seismicity, due to its continuous nature. This study could provide a better understanding of the mechanisms causing seismic velocity changes at South Sister.

The snowball Earth hypothesis states that between ~720-635 Ma Earth underwent glaciations during which the planet was covered completely in ice. Scientists use carbonate deposits, called cap carbonates, which appear atop snowball Earth glacial deposits to mark the end of these glaciations. Cap carbonate deposition is currently thought to have occurred during extreme stages of the chemical weathering (breakdown of rock by chemical reactions) that followed snowball Earth. However, there is insufficient geochemical evidence to confidently determine which stage–extreme, mild, or otherwise–of chemical weathering intensity the carbonates were deposited in. Magnesium, Mg, isotope abundance is useful in tracking chemical weathering events because of magnesium’s sensitivity to chemical weathering intensity. Data collected from rock samples from the Yangtze Formation in South China support the conjecture that chemical weathering was most intense immediately following snowball Earth, but it was not until chemical weathering slowed down that cap carbonates were deposited. This scenario allows time for continental chemical weathering to occur and calcium and magnesium cations to become available for the production of carbonates. To revise the snowball Earth hypothesis with this information, samples from more than one region are needed to apply this timeline globally. I will dissolve rock samples collected from the Amazon Craton in Brazil and study the sample powders using mass spectrometry to collect Mg isotope abundance data. I expect the data collected from these samples to resemble the data collected from the Yangtze Formation cap carbonates. This corroboration will help piece together the puzzle of the Snowball earth timeline.

Stromatolites are laminated sedimentary constructions that are thought to be built by microbes. These structures have the potential to serve as indicators of environmental or biological change throughout Earth history. Here, I aim to understand how the study of what controls a stromatolite's shape has changed through time. In particular, I am interested in understanding the extent to which missing branches of study, or what I term “ghost literature,” have contributed to the corpus, and if their absence imparts bias in contemporary approaches to the study of stromatolite formation. To this end, I have developed computational tools to analyze the literature. To compile publication data, I utilize a self-authored computational toolset to probe existing literature databases, including xDD (formerly known as GeoDeepDive), and Web of Science. I examine the compiled data using visualizations and statistical analyses. Through these analyses, I uncover publication biases by assessing how references might be over- or under-cited in the corpus. Furthermore, I highlight conceptual frameworks for stromatolite formation that have been lost or understudied by reviewing text from under-cited references. This project is the first step in a much larger project that will attempt to quantitatively link stromatolite shape to both environmental and biological factors, which can unlock their potential as windows into our planet's past.

Archaeal cellular envelopes are quite simple compared to bacterial surfaces. Unlike bacterial cells, S-layers are the dominant component of most archaeal surfaces. Archaeal S-layers are composed of proteins or glycoproteins symmetrically arranged in an almost crystalline lattice. S-layers are in direct contact with the surrounding environment and facilitate important processes including protection, cell adhesion, molecular sieving, ion trapping, and nutrient adsorption. It is clear that S-layer proteins play an important role in an organism's ability to survive, especially within extreme environments. However, it remains unclear if S-layer proteins change in response to environmental stressors such as increasing temperature. This project is aimed at quantifying variation in bulk protein concentrations within microbial cultures containing a hyperthermophilic deep-sea methanogen (Methanocaldococcus sp. FS406-22) grown at 65, 73, and 85°C. Total protein concentrations were gathered via spectrophotometric analysis after growth. Optimal growth temperature for Methanocaldococcus sp. FS406-22 is 65C but can grow at temperatures up to 92°C, the highest known temperature limit for biological nitrogen fixation. I hypothesize that changes to Methanocaldococcus sp. FS406-22 S-layer proteins will be observed in order for the organism to acclimate to more extreme growth conditions. These data give important preliminary information regarding Methanocaldococcus sp. FS406-22 ability to physically adapt to changing environmental conditions. This project ultimately provides context for future work to be directed at exploring not just if S-layer proteins change but also how.

Increased awareness of the complexity and importance of soil ecosystems has led to a surge in “regenerative” agricultural practices, which build topsoil and improve soil fertility and nutritional quality of produce. Such practices also sequester carbon in soils, reduce topsoil erosion and reliance on synthetic fertilizers, and increase microbial content and water storage capacity of soils, avoiding many of the negative environmental and ecological impacts caused by more conventional forms of agriculture. While there is substantial anecdotal evidence for the success of regenerative farming, quantitative studies that support farmer experiences are limited. This study aims to help bridge this gap by examining soils in the Puget Sound region to evaluate differences between areas managed regeneratively and conventionally. I visited five local regenerative farms and took two sets of soil samples from each: one from a plot managed regeneratively, and one from a portion of the farm that has not yet transitioned from conventional to regenerative management. Each set of soil samples consisted of soil cores to test for soil organic carbon (SOC), and a soil pit to examine soil horizons. I determined SOC using loss-on-ignition tests, and topsoil depth by measuring the thickness of the A-horizon in the soil profile. The data show that topsoil managed with regenerative practices can be up to 4 inches deeper and contain up to 20% more SOC than when managed conventionally. Within the regeneratively managed plots at the UW Student Farm, there is a strong correlation between the age of the plot and topsoil depth, suggesting growth of topsoil over time. While these findings align with the results of other studies, a more nuanced understanding of how topsoil formation processes and soil ecosystems develop under regenerative management is necessary to support large-scale transitions towards more sustainable agriculture.

The weathering—or breaking apart by physical and chemical means—of common silicate (silicon dioxide based) minerals is a major mechanism of the freeing and distribution of nutrients into the environment at large, as well as a major component of the planetary carbon cycle. Effective extraction of nutrients by weathering is particularly important to organisms living along bedrock surfaces, such as the bacteria found in the basal ice of the Greenland ice sheet. Microbial surfaces have reactive sites which bind to ions and minerals, and may be a mechanism for internalization of nutrition in the incredibly harsh Greenland ice sheet basal water pores. These reactions may encourage the further dissolution of minerals as their constituent ions are pulled out of solution. Therefore, my research seeks to understand the effects that bacterial surface binding has on the dissolution of gneissic bedrock from the Greenland ice sheet’s base. I hypothesize that the presence of endospores will increase the rate of silica dissolution above control sample rates. To test this hypothesis, two experiments were performed. Ground gneiss obtained from the base of the Greenland ice sheet was placed into dialysis pouches. One dialysis pouch was placed in water containing Bacillus subtilis endospores and the other dialysis pouch was placed in pure water. The dissolution products were monitored over time. Initial results suggest that increased mineral dissolution occurs in samples with endospores present, implying that endospore surface reactivity may have important implications in chemical weathering processes. Better understanding of weathering processes, particularly as they are used to extract nutrients and control climatic conditions, allows us to better understand habitability in our present, past, and changing future.

This research investigates the behavior of magnesium isotopes during the dehydration process of subducting oceanic crust. The aim is to understand how magnesium isotopes behave during the metamorphic process of subducting oceanic crust up to eclogite-facies, and whether potential magnesium isotope heterogeneity in the altered oceanic crust can be retained in the dehydrated residual eclogites. The research utilizes geochemical methods to analyze eclogites from Europe.

Specifically, this project involves the use of a Nu Plasma II multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) to measure Mg isotopes in the rock samples. The samples are weighed and digested first, followed by column chemistry to purify the Mg fractions. The purified Mg fractions are finally measured using MC-ICP-MS to determine their Mg isotope compositions. The data will be interpreted to gain insights into the behavior of magnesium isotopes during the dehydration process of subducting oceanic crust.

Preliminary results reveal significant heterogeneity in the Mg isotope composition of the eclogites. These results have important implications for our understanding of role of oceanic crust recycling in chemical evolution of the Earth's mantle.