Structure and Tectonics (9:30am - 10:30am)
Alysa Fintel
Multi-scale Characterization of a Major Subduction Zone Splay Fault: the Deception Creek Strand of the Patton Bay Fault, Montague Island, Alaska
We conducted a field study of the Deception Creek strand fault zone in June 2022 that included outcrop-scale mapping, a seismic refraction survey, and sample collection to analyze the properties of this large-displacement brittle fault zone. The Patton Bay Fault (PBF) on Montague Island, Alaska had surface rupture and up to 10 meters of vertical displacement in the 1964 Mw 9.2 megathrust earthquake. The Deception Creek strand of the PBF did not have slip in 1964 but is exposed in the coastal intertidal zone and upland that reveals a wide, mature fault zone. In addition to this well-developed fault zone outcrop, the fault trace is located at the base of the main topographic break of the island, suggesting that the Deception Creek strand is the main trace of the PBF. The fault zone is approximately 150 meters wide from hanging wall to footwall and consists of an incohesive gouge fault core and a highly fractured damage zone that is hosted in wallrock consisting of well-bedded and lithified Orca Group sandstone and siltstone turbidites. The gouge core is 8-10 meters wide with splays of secondary slip surfaces and cataclasite patches extending an additional 20 meters into the hanging wall. The damage zone grades over ~50-100 meters from cataclasite-rich and highly fractured and disrupted lenticular chunks of bedding to Orca Group wallrock, unaltered by movement on the Deception Creek strand, which is typified by moderate to steep dip and localized folds and small faults. Samples representative of the different structural zones were taken for laboratory analysis of the fault zone evolution. Microstructural analysis, bulk composition analysis, and ultrasonic velocity measurements from the samples will identify composition, alteration, and deformation (including changes in elastic properties) across the fault. We acquired a 120-meter long refraction seismic line across the fault zone, near-perpendicular to strike, with 3-meter geophone spacing and 6-meter hammer shot spacing. This refraction study will allow us to further characterize subsurface structure and potential velocity changes across the fault zone. The scope of this study from micro- to outcrop scale provides insight into the architecture of subduction splay faults and provides a framework for three-dimensional models of the seismic attributes of submarine splay faults.
Jason Ott
Preliminary experimental constraints on the rheology of mafic blueschists
The strength and deformation behavior of the subduction-interface plays a central role in generating geological hazards. Yet, the rheology of many subduction lithologies that deform along the plate interface remain poorly constrained. Between the base of the subduction seismogenic zone and the sub-arc (~35-100 km), high-P low-T metamorphism of subducting ocean crust produces mafic blueschist. Observations of naturally deformed blueschists exhumed from these depths suggest they accommodate significant strain—largely partitioned into the ubiquitous sodic amphibole glaucophane (gln). Thus, constraining the absolute strength of gln, and by extension blueschist, will improve our understanding of plate interface rheology at these depths. In order to provide these rheological constraints, we experimentally deformed gln in a high-P high-T deformation apparatus at relevant P-T conditions. Fine grained gln aggregates (10-20 µm) were hot-pressed for 16 hours at T=650℃ and P=1.5 GPa, then deformed at temperatures from 650-750℃ at strain rates (γ ̇) of 10-3-10-4 s-1. Glaucophane’s peak strength decreases substantially from τ~1000 to ~200 MPa with a 100℃ temperature increase. Preliminary calculations estimate an activation energy (Q) of ~200-400 kJ/mol. Stress-stepping experiments yield a stress-exponent of n ≈ 5, consistent with deformation by dislocation-assisted motion. Compared to the hot-pressed starting material, microstructures in deformed samples show increased evidence of intragranular deformation, subgrain boundary recrystallization, and strong crystallographic preferred orientations supporting the activation of dislocation-creep-accommodated deformation. Similar microstructures in our lab-deformed samples and exhumed, naturally deformed blueschists from various subduction zones imply that our experiments accessed the deformation regime experienced by these naturally-deformed blueschists. This suggests that deformation along the subduction interface at blueschist conditions is largely accommodated by dislocation creep in gln. Based on the high temperature-sensitivity of gln’s peak strength in the dislocation-creep regime, we propose that the strength of blueschist along the plate interface rapidly decreases with increasing temperature/depth in the subduction zone.
Anna Ledeczi
Detecting Recent Splay Fault Activity in the Cascadia Accretionary Wedge using High-Resolution Seismic Reflection Profiles
Splay faults, which branch from the main plate boundary fault in the accretionary wedge with a steeper dip angle and a closer proximity to shore, can result in larger tsunamis with shorter warning times upon rupture compared to megathrust-only fault ruptures, posing an increased hazard to coastal communities. Slip occurred on splay faults during several of the last century’s biggest subduction zone earthquakes (1964 Mw 9.2 Alaska, 1944 Mw 8.1 and 1946 Mw 8.1 Japan, 2004 Mw 9.1 Sumatra), but our understanding of potential active splay faults and their hazards in Cascadia remains limited. In order to identify the most recently active and therefore potentially seismogenic splay faults in the Cascadia accretionary wedge offshore Washington state, we conduct a detailed stratigraphic and structural interpretation of near-surface deformation in the wedge and in shallow slope basins. We use high-frequency sparker seismic data to examine the record of deformation in these basins and the upper ~1 km of the surrounding accreted wedge sediment packages. Observations of folded and faulted strata allow us to determine the history of deformation for each basin and develop an integrated stratigraphic and structural sequence of events for each basin. Several basins display near-surface deformation of the presumably youngest sediments, indicative of recently active splay faulting in portions of the accretionary wedge. Most previous work has focused on the deep structure of the accretionary wedge or on the surface morphology and cores of the uppermost few meters of sediment for evidence of recent earthquake activity; this study bridges the two scales and allows us to connect deep fault structure in the accretionary wedge to near surface deformation, improving our overall understanding of splay fault activity in Cascadia. In this work, we make a preliminary identification of key locations in the wedge where recent deformation has been most focused, and therefore future involvement in co-seismic slip during the next megathrust event is most likely.
Emma Heitmann
Paleoclimate reconstruction of the Miocene Bidahochi Formation and implications for southwestern Colorado Plateau uplift
Understanding the causes and consequences of topographic change is important for understanding tectonic processes and the co-evolution of earth’s surface, climate, and life. An important question about paleotopography is the origin and elevation-history of orogenic plateaus, which are a product of tectonic and geodynamic forces and influence global climate, landscape evolution, and ecosystems. The Colorado Plateau region is an interesting place to investigate this question because scientists have long debated both the causes and consequences of uplift. This region resides at an average elevation of ~2 km above sea level, but ~90 Ma marine deposits show that the region was once near or below sea-level. Several mechanisms have been proposed to elevate the region without significant upper-crustal deformation of the plateau, each with testable predictions of surface elevation gain and timing. Thus, accurate paleoelevation constraints can have implications for illuminating tectonic or geodynamic drivers of uplift, as well as how uplift influenced the landscape, ecosystems, and climate. Here, we aim to constrain the uplift history of the Colorado Plateau by studying the Bidahochi formation, a lacustrine and fluvial system that deposited sediment from ~16 to 6Ma on the plateau. To do this, we plan to reconstruct surface temperature using carbonate-clumped-isotope thermometry throughout the Bidahochi formation, and then evaluate the data within the context of climate models. Surface temperature is influenced by altitude, seasonality, and climate. I have made predictions of what surface temperature you expect, controlling for the prior variables (elevation change, climate change, and seasonal bias of proxy record). I test for different hypotheses: 1) there was no change in elevation during deposition of the Bidahochi formation, and the depositional elevation is comparable to modern; 2) elevation increased during deposition of the Bidahochi formation, and 3) elevation did not change during deposition, and depositional elevation is lower than modern. These results provide a possible range of expected temperatures that will be crucial for evaluating my dataset.
Geophysics (10:45am - 11:45am)
Manuela Köpfli
Random Forest at an Alpine Torrent unveils how Debris Flows are fed
Debris flows are potentially hazardous. Therefore it is important to understand how and when they occur. By studying much smaller but more frequent slope failures in a debris flow catchment we gain insights into the supply of material that is needed to form larger debris flows. Understanding relations between the local weather and such small slope failures is the first step towards forecasting debris flows.
To take this first step, we choose one of the most active torrents in Europe, Illgraben in Switzerland. With steep slopes (40 degree) consisting of porous Dolomite and a 10km2 catchment area reaching from 600 m.a.s.l up to more than 2700 m.a.s.l, Illgraben is an ideal natural laboratory for studying slope failures.
We use seismometers as a sensitive tool to detect small slope failures. Continuous weather data, temporal ground moisture data and optical imagery complete our dataset. We run machine learning algorithms on our continuous seismic data for slope failure detection. These algorithms outperform conventional automatic event detection methods such as RMS or STA/LTA which have difficulties in distinguishing slope failures from various other seismogenic events. We train a binary random forest classification algorithm with 23 labeled slope failure events and 202 noise windows. Tested on 17 events and 101 noise windows including thunder, earthquakes and continuous noise, the algorithm reaches an accuracy of 94% for slope failures and 91 % for noise.
We find an annually repeating decrease of slope failure activity at Illgraben towards the end of summer. In turn, the highest activity occurs when snowmelt and strong precipitation events fall together. These observations suggest that a feeding limit is reached over the summer and an additional frost cracking during winter is required to provide new loose material for consecutive slope failures that may result in potentially hazardous debris flows.
Veronica Elgueta
Earthquakes with DAS in the Pacific Northwest
Distributed acoustic sensing (DAS) has recently become a powerful tool for seismologists to study complex systems providing both high spatial and temporal resolution with low deployment and maintenance costs. Exploratory research conducted at the University of Washington is using DAS in the Puget Lowlands, Washington, to monitor local, regional, and global earthquakes, as well as tectonic tremors, and related phenomena.
This work explores the DAS dataset coming from both cables deployed in the Puget Lowlands. We will call one cable Whidbey (from Camano Island to Whidbey Island), and the second one SeaDAS (runs from the UW Seattle Campus to the UW Bothell Campus). About one year of data has been collected. We have cataloged local and regional earthquakes with a minimum magnitude of 3.0w and within an epicentral distance of 600 km using the Whidbey cable. As a result, we have found that the channels of the cable that are on the seafloor are more sensitive to earthquake signals than the channels of the cable that are located on the surface. Also, we have been working on cataloging global earthquakes with a minimum magnitude of 7.0w using SeaDAS and Whidbey cables. Both cables are able to capture the waveform from these high-magnitude earthquakes. For local and regional earthquakes, which have smaller magnitudes, we can also visualize and get the waveforms from these lower magnitude earthquakes and are working on streamlining the characterization of these signals using the Whidbey and SeaDas cables jointly.
Jensen DeGrande
Evaluating Long Short-Term Memory (LSTM) network for real-time high-rate GNSS displacement predictions
We present a neural network optimized for producing GNSS displacements to explore machine learning capabilities in forecasting ground motions for earthquake early warning and to improve our understanding of ground motion in real-time. For earthquake early warning, displacements at GNSS receivers are currently being incorporated into the ShakeAlert system, but displacements in real-time are problematic due to issues with phase ambiguity fixing, cycle slips, and loss of satellite lock as well as dilution of precision from satellite network geometry. These errors can lead to anomalous motions of up to a meter. Raw GNSS observations for velocities can utilize orbits (relative positions) and remove uncertainties caused by path errors, leading to a higher precision observation than the displacements. In general, peak ground velocity is diagnostic of earthquake damage and displacement is diagnostic of total moment release, so obtaining these observations at the highest fidelity is crucial for rapid earthquake source estimation. Since processing raw GNSS velocities gives a higher precision observation, we aim to derive displacements from velocities using a machine learning approach. We use a Long Short-Term Memory (LSTM) network, a recurrent neural network (RNN) with the ability to remember values for an arbitrary amount of time, for time series prediction of the GNSS displacements. The input variables for the model are three-component GNSS velocities derived from the SNIVEL software package, with the possibility of including signal to noise and phase observables, and the output variable is the GNSS displacement time series. The GNSS displacement is validated against the displacements computed with the precise point positioning code GipsyX. With over 2250 1-Hz observations from 82 different events ranging from M4.9 to M9, we have ample data to train, validate, and test the network on. We train several neural network instances on random selection of train/validation/test split for redundancy and shuffle data input order for each instance. By computing the GNSS displacement from GNSS velocities, we produce a higher precision observation, a low-cost method for monitoring deformation without the traditionally high overhead associated with real-time GNSS processing, and the possibility of direct onboard receiver transmission of displacements.
Jess Ghent
Monitoring Tonga Eruption Plume Using GNSS-Derived Atmospheric Wet Delay
The climactic January 2022 eruption of Hunga Tonga-Hunga Ha’apai (HTHH) produced a plume that was unprecedented in its size and rate of expansion. Although there are a number of tools by which to monitor plumes during an eruption, this task remains a challenge in remote or poorly equipped areas. As the contents of volcanic plumes pose a significant hazard to both local communities and proximal/distal aviation, it is worth pursuing a holistic approach to tracking plume development. Using Global Navigation Satellite Systems (GNSS), eruption columns can be detected via atmospheric wet delay, or the time delay caused by precipitable water along the satellite-to-receiver path. With this method, we measure a large departure from background wet delay levels during the first two hours of the HTHH eruption, on the order of several meters of signal delay. Comparison to the prior three days highlights the significance of atmospheric perturbations on January 15 and features a smaller deviation on the previous day, which may be attributed to an earlier eruption sequence. Future work will include utilizing the wet delay to explore temperature dynamics within the plume, which are poorly understood at this time and which play a role in the rate of plume expansion.
Geochemistry (2:00pm - 2:30pm)
Jinqi Wu
Investigation of Magnesium isotope behavior during metamorphic dehydration of subducting oceanic crust
Recycling of oceanic crust driven by plate tectonics has long been suggested to play one of the most important roles in producing compositional heterogeneity in the Earth's mantle. Previous understandings of this process mostly relied on trace element and radiogenic isotope geochemistry, which can sometimes be difficult to distinguish from the influence of sediment recycling into the mantle. Magnesium (Mg) occurs as a major element in both oceanic crust and the mantle. Recent studies have revealed that Mg isotope exchange between oceanic crust and seawater during seafloor alteration can lead to large Mg isotope fractionation in the altered oceanic crust. Therefore, once the seawater-altered oceanic crust is subducted, the Mg isotopic compositions of local mantle domains may be modified by this process, which may help to explain the variable Mg isotopic compositions observed in some mantle-derived lavas. Nevertheless, it is still not clear whether the characteristic Mg isotopic heterogeneity in altered oceanic crust can survive subduction-zone metamorphic processes. To address this issue, we investigated the Mg isotopic compositions of high- to ultrahigh-pressure eclogites that represent metamorphic equivalents of oceanic crust. We found that these eclogites display larger Mg isotopic variations than fresh MORB, but their isotopic compositions show no systematic trend with metamorphic grade and proxies for metamorphic dehydration. Such Mg isotopic signatures are most likely inherited from isotopic heterogeneity produced by seafloor alteration of their oceanic crust protoliths. Therefore, subduction-zone metamorphism has a limited influence on Mg isotopic compositions of subducted oceanic crust, suggesting that Mg isotopes could be used as a tracer of recycled altered oceanic crust in the mantle.
Autum Downey
Microbial Velcro: Quantifying how ‘sticky’ the cell surface of deep-sea methanogen Methanocaldococcus sp. FS406-22 is under various aqueous conditions
Microbial life source essential nutrients from the surrounding environment. However, prokaryotes lack the physiological ability to ‘reach out’ and grab the required compounds. Instead, microbes acquire essential compounds through passive electrostatic interactions between their outermost surface layer and the surrounding environment. As such, it would be advantageous for microbial cells to exhibit some mechanism in which the passive interactions between the cell surface and essential nutrients are thermodynamically favored over other non-essential compound interactions, especially within extreme or nutrient limited environments. Deep sea hydrothermal fields represent one such environment. At these 'extremes', methanogens represent the foundation for ecosystems supported by geochemical energy, rather than photosynthetic productivity. This suggests an enhanced 'sensitivity' to changes environmental conditions. This work was aimed at quantifying the abundance of cell surface sites able to participate in passive electrostatic interactions with the surrounding environment of a deep-sea methanogen, Methanocaldococcus sp. FS406-22. These data are an essential first step in understanding how deep sea methanogens are able to mitigate such a sensitivity to chemical changes within the surrounding environment and thrive in low nutrient conditions. Here we characterized the cell surface reactivity in terms of thermodynamics in order to elucidate the driving force behind these electrostatic interactions (enthalpy or entropy driven). Surface reactivity was quantified within a 0.4 M NaCl solution (simple electrolyte solution) and a 0.56 M ‘mock’ seawater solution to explore thermodynamic changes to the cell surface in response to changing conditions. These data represent some of the only thermodynamic characterization of cell surface reactivity within a near ‘natural’ aqueous seawater solution.
Petrology/Volcanology (9:30am - 10:15am)
Peter Lindquist
Deformation and dehydration in subducted metabasalts of the Catalina Schist
Subduction zones are loci of major geohazards, and fluids produced by the loss of mineral-bound water in subducting rocks play an important role in both seismic and volcanic processes. Basalts in subducting oceanic crust in particular can carry significant quantities of water into subduction zones, but how these fluids are released at depth, move through the subducting slab and plate interface, and affect the chemistry and deformation of rocks is not well understood from the geological perspective. Metabasalts from blueschist to amphibolite facies conditions (ca. 400–550°C and 0.9–1.3 GPa) in the Catalina Schist from California provide an opportunity to study metamorphic and deformation processes in rocks that experienced the pressure-temperature conditions at which slow slip events and tectonic tremor occur in modern subduction zones. In the Catalina Schist, metabasalts from similar pressure-temperature conditions exhibit a broad diversity of deformation fabrics and vein morphologies. This work is starting to explore how variations in metabasalt chemical composition may contribute to variations in the strength, metamorphic dehydration histories, and fluid pathways of metabasalts.
William Hoover
Forming a slow slipping subduction interface: P-T-t-X history of metasomatic rocks
The interface between subducting and overriding plates is fluid-rich, chemically dynamic, and seismogenic. Constitutive relationships and microstructural evidence indicate that talc-rich rocks produced by metasomatism at this interface host episodic tremor and slow slip (ETS), but the chemical pathways producing talc and other metasomatic minerals remain unclear. Constraining the pressure-temperature-time-chemical evolution of such metasomatic rocks can reveal the full extent of their rheologic impact. We combine field mapping, geochemistry, geochronology, and thermometry to determine the P-T-t-X history for a suite of slow slip-hosting talc-, chlorite-, and amphibole-rich metasomatic rocks from the Catalina Schist (California). These rocks compose the matrix of an exhumed subduction interface shear zone where metasedimentary protoliths were converted to chlorite and actinolite schists and mantle wedge ultramafic rocks were converted to talc and actinolite schists. Local exchange of Na and LILE from metasedimentary to ultramafic rocks, and Mg, Fe, Cr, and Ni from ultramafic to metasedimentary rocks was complemented by addition of Ca from infiltrating fluid. Epidote veins in underlying metabasalts suggest dehydration of these rocks released the infiltrating Ca-bearing fluid. Zr-in-rutile and Raman spectroscopy of carbonaceous material thermometry of the metasomatic rocks indicate syn-kinematic metasomatism began during prograde subduction and continued through peak conditions comparable to those of modern ETS. Petrochronology of rutile and titanite overgrowths suggests the rutile-to-titanite reaction was catalyzed by metasomatism and constrains the timing of metasomatism to ~100 Ma consistent with subduction of this portion of the Catalina Schist. Both local exchange between juxtaposed lithologies and external fluid infiltration were key in driving metasomatism of the subduction interface and this work suggests Mg loss as a new pathway for talc formation in ultramafic rocks. Metasomatism spanned prograde through peak subduction and the source region of ETS representing a dynamic and evolving system impacting interface rheology across a broad range of depths.
Nicole Aikin
Monazite petrochronology reveals the lifecycle of orogen: example from the upper granite gorge, Grand Canyon
The timescales, durations, and 4-D evolution of metamorphism and ductile deformation throughout continental collision control orogenic expression and influence dynamics. Yet the evolution of these processes often remain relatively unconstrained due to incomplete exposures or lack of detailed in-situ petrochronology to quantify P-T-d-t. The Grand Canyon’s Upper Granite Gorge (Arizona, USA) preserves a 68 km (42-mi) long 100% exposure of Paleoproterozoic crystalline basement that formed within a long-lived convergent boundary along southern Laurentia. We investigate timescales of orogenic evolution using in-situ monazite Electron Microprobe chemical age data from Vishnu Schist metapelites in two adjacent tectonometamorphic blocks. Both blocks experienced prograde metamorphism and deformation (D1) but were variably overprinted and transposed during a second phase of deformation (D2). We contrast new monazite petrochronology from the Clear Creek block (CCb), which preserves D1 structures and reached peak conditions of 500°C and 6 kbar during D2, with new and previously published dates from the Mineral Canyon block (MCb), which is pervasively deformed during D2 and reached peak conditions of 700°C and 6 kbar during pegmatite emplacement. Across both blocks, metamorphic and magmatic monazite and xenotime yield U-Pb ages spanning deposition (ca. 1745 Ma), prograde (ca. 1727-1704 Ma), peak and retrograde thermotectonism (ca. 1702-1690 Ma), and rapid decompression to mid-crustal residence (ca. 1690-1674 Ma), reflecting the entire duration of crustal accretion during the Yavapai orogeny. Monazite rims yield U-Pb ages that are interpreted to reflect reactivation of Yavapai structures during Mazatzal orogenesis (ca.1660-1647 Ma), mesoproterozoic tectonism (ca. 1560-1522 Ma), and Picarus orogenesis (ca. 1497-1413 Ma), although the latter are exclusive to MCb. Monazite rims yielding U-Pb These temporal patterns are consistent with previous geochronological studies in the region suggesting the Yavapai juvenile island arc accreted to the proto-North American continent over a 60 My interval. Additionally, results raise new questions regarding how subsequent deformation is accommodated in pre-existing zones of weakness in the middle crust throughout the lifespan of a collisional boundary.
Geobiology (2:00pm - 2:30pm)
Ben Lloyd
An automated method for morphological analysis of leaf cuticle with implications for paleoecology and paleoclimatology
Fossilized leaf cuticle - the waxy surface of leaves common to geologic sediments from the last 400 million years - remains an underutilized data source for reconstructing paleoclimate and paleovegetation assemblages. The morphology of a leaf’s epidermal pavement cells reflects the environmental conditions of its growth. Traditionally, cell morphology was determined by hand-tracing cell walls using digital tools. This is a slow and tedious process, with cell-outline quality highly dependent upon the setup used, and the person tracing the image. To avoid the issues associated with hand-tracing cell outlines, we developed a user-friendly automated image analysis workflow using ImageJ and R. Our code allows for the automated generation of large cell-shape datasets from images of leaf epidermis. Use of this method results in a higher degree of cell-tracing consistency, while allowing for increased sample sizes by drastically decreasing the time required to generate these data. We apply this method to an image set of 130 vouchered herbarium specimens extracted from The Cuticle Database (cuticledb.eesi.psu.edu), representing 127 species in 87 genera from 36 families. Images were chosen to maximize taxonomic breadth and span the range of cell shapes and sizes, utilizing the specimens with the highest quality image of the upper cuticle. For each image, our workflow produces a set of vectorized cell outlines, with associated shape parameters. Our initial results suggest that cell measurement ranges overlap between the hand-drawn and automated datasets for the same images, but they follow slightly different distributions, which might be expected given our increased sample size and different sampling strategy. This workflow can now be used to reconstruct parameters such as Leaf Area Index, and thus the canopy structure of forests in deep time, more effectively utilizing the vast repository of leaf cuticle in the fossil record.
Vigash Ravi
Provenance of Illicitly Traded Pangolin Species From Stable Isotope Analysis of Scale Samples
Pangolins are the most widely trafficked mammal in the world. Pangolin scales are smuggled for use in traditional medicine and this is a concern due to all eight species of pangolins; four in Africa and Asia, respectively, currently being in the vulnerable to critically endangered category. My research provides insight into the practices and routes of smugglers using stable isotope analysis to obtain information on locality of origin from scale samples of Smutsia gigantea, Smutsia temminckii, Phataginus tetradactyla, and Phataginus tricuspis, the four species of pangolins native to the African continent. I collected powdered scale samples from the four pangolin species and analyzed the samples using an elemental analyzer attached to an isotope ratio mass spectrometer (EA-IRMS). Scale samples were sourced from recent seizures in multiple ports. Data from the EA-IRMS provide Sulfur, Carbon, Nitrogen and stable isotope composition estimates. Data from the multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) provide Strontium stable isotope composition estimates. This information was then used to place individuals into groups and then predict where those groups lived prior to being poached. Better understanding of smuggling routes and poaching habits is an aim of this project. Stable isotope analysis may also help our collaborators identify the pangolin species when scale samples contain insufficient or otherwise poor quality DNA. This project has valuable implications in future forensic studies of organic materials and will lead to better policing and policy making with regards to pangolin conservation.
Poster Session (3:00pm - 5:00pm)
Hannah Greaney geomorphology
Analyzing travertine deposits from Dixie Valley
This research is exploratory of Dixie Valley, possibly relating fluids and faulting, using a sample rock from an area with travertine, calcite veins, and calcite cemented gravels along or offset by a Quaternary fault. Some specific questions addressed will be the isotope chemistry and trace elements recorded in the rock. The methods used in this project will include qualitative and quantitative measurements like X-ray fluorescence, thin section analysis, oxygen and carbon isotope measurements, UV lights, and Cathode Luminance. Anticipated findings include an element map and transect variation of the layers across the rock and a map to understand more with thickness, cross cutting, variations in layers with crystal form, color, and geochemistry. This exploratory research has an ongoing hypothesis: the rock records the history of variations in fluid flow along this fault zone; we can interpret these variations in context with other data from the region that might help us connect back to the bigger questions of past climate, earthquakes, etc.
Heather Maran geomorphology
Elliott Bay bathymetric evolution since 1875 based on historic mapping
Elliott Bay, an embayment within the inland estuary of Puget Sound, has undergone extensive geologic and anthropogenic influence. Processes which have modified Elliott Bay include glacial scour and sediment deposition, tectonic activity, volcanic sediment input, and anthropogenic dredging and disposal of sediment. This study compares bathymetry in Elliott Bay from 1875 hydrologic depth surveys to modern-day bathymetric data from NOAA. A georeferenced 1875 survey map of Elliott Bay containing over 2,000 depth points was interpolated using natural neighbor to produce a raster dataset of bathymetry. The 1875 bathymetry is compared to modern bathymetry and isopach maps were created in ArcGIS Pro to evaluate areas of depth difference, some of which we interpret as areas of sediment accumulation and removal. Shallow seismic reflection profiles were compared with areas of apparent accumulation to ground-truth the interpolation methods. Elliott Bay is shallower in regions of anthropogenic sediment input, such as near the Denny Regrade spoil bank and modern disposal sites, as well as near regions of past landslide history. Areas of sediment removal are prominent along the shoreline of Elliott Bay, off the slopes of the Duwamish Head, and within channelization for ports including the Duwamish waterway. This study is a part of a broader investigation to better understand the history of geologic and anthropogenic processes influencing sedimentation in Elliott Bay.
Akash Kharita geomorphology
Characterizing slope failures using regional seismograms
Surface event parameters are typically estimated using field surveys or satellite imagery. These methods have poor temporal resolution, and potentially poor spatial resolution depending on the data and have uncertainties in the measurements that may be challenging for hazard characterization. The seismic waves generated by these surface events carry information about their source. Therefore, seismic monitoring provides an excellent opportunity to monitor surface events. By understanding the relationships between the time-frequency representation of the seismograms and the surface event dynamics, one can estimate event parameters for the small to moderate sized slope movements for which event parameters cannot be estimated using traditional methods. We explore the relationship between over 300 features extracted from seismograms and three surface event parameters - volume, runout distance and drop height - for the events in IRIS Exotic Seismic Event Catalog (ESEC). Our primary motivation is to find features that show high correlation with rockfall event parameters. We use correlations and a random forest algorithm. Our preliminary results indicate that certain features characterizing the spectral content of the seismograms show high correlation with all the event parameters. Some of these features show even better correlation compared to some of the features previously chosen by other studies (Dammeier et al. 2014, Manconi et al. 2016, Hibert et al. (2017a, b)).
Marquis Richardson geomorphology
Glaciers or Subduction: Identifying the Provenance of Garnet in Beach Sand on the Olympic Peninsula of Washington
Garnet-bearing sand has been identified along the coast of Washington at Ruby and Rialto
Beach. There is currently no identified local source rock and no conclusion about the provenance of the garnet minerals: are they sourced from glacial sediments or subduction zone rocks? When garnets form, they can contain small inclusions of other minerals that provide constraints on the pressure and temperature of mineral growth. I am investigating the inclusion mineral assemblages found within the garnet to determine their metamorphic facies and match this with possible source rocks in the region. There are two possible locations of provenance for the garnet: the Cascadia Subduction Zone or the North Cascades/British Columbia (BC). I collected samples of the garnet sand from both Ruby and Rialto Beach and used a Frantz Magnetic Separator to isolate the garnet for grain mounts polished to expose the interior of crystals. A scanning electron microscope (SEM) and energy dispersive spectroscopy were used to identify the composition of the index minerals within the garnet to locate their metamorphic facies and provenance region. The results of the SEM analysis will potentially show high-pressure mineral inclusions (lawsonite, glaucophane, omphacite) and provenance from the Cascadia Subduction Zone or higher temperature metamorphic minerals (staurolite, sillimanite, biotite) and provenance from the North Cascades/BC. If subduction zone provenance is determined, this garnet could represent material brought to the surface from an active subduction zone, which can be used to directly compare with active processes in the Cascadia Subduction Zone today. If
North Cascades/BC regional metamorphism provenance is determined, a better understanding of glacial ice transport during the last global cooling event can be developed.
Julia Macray geomorphology
Assessing the Effects of Regenerative Agriculture in the Puget Sound Region on Topsoil Depth and Soil Organic Carbon Content
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.
Ian McLennan geomorpholgy
Mapping the Kyle and Sou Hot Springs, Dixie Valley, Nevada
The greater Dixie Valley region of Nevada is located in a zone of continental extension that has allowed for the formation of hot springs along active normal faults. The hot springs are associated with travertine mounds, carbonate deposits precipitated from hot-spring water. I am working to determine the relative age of these mounds compared to other features that are seen on the landscape including alluvial fans, paleolake shorelines, and fault scarps. I use ArcGIS Pro with topographic data and aerial imagery to map these features and describe the spatial relationships between them. Using Landsat 8 imagery, I am creating false color images for mineral indexes to highlight the presence of mineral materials based on their reflectance and absorption wavelengths, These indexes will both aid in mapping alluvial fan surfaces and may help in determining the approximate age of the mapped features based on the presence of chemical weathering products. Combining observations of the cross-cutting relationships of the mapped features and their minimal composition will aid in determining their relative age. Providing relative ages for the features in the Dixie Valley and surrounding region will help create a geological history of the area which will provide context for further interpretation of the hot spring deposits.
Elizabeth Davis structure and tectonics
Recurrence interval of large Seattle Fault earthquakes inferred from submerged terraces in Puget Sound
The Seattle Fault Zone, which crosses the city of Seattle, produced a M~7.5 earthquake about 1100 years ago, resulting in cascading hazards across the region that would be devastating if they occurred today. Mitigating the hazard of a future earthquake depends in part on producing earthquake recurrence intervals grounded in geologic evidence. Current hazard estimates allow for a 5000-year recurrence interval for such events, though hypotheses proposed based on geomorphology (by Thorson, doi: and Haugerud, doi: 10.1130/2017.0049) suggest the recurrence interval could be twice that long. This study digs into the recurrence question by evaluating the proposed hypotheses based on submarine geomorphology. Submerged benches in Puget Sound have been attributed to shorelines produced by a sea-level lowstand at least 11,000 years ago. Shorelines on land were uplifted ~6 m in the earthquake 1100 years ago; shorelines 11,000 years old might be expected to record an amount of uplift consistent with however many earthquakes have happened in that time. I paired existing NOAA bathymetry with new and legacy seismic reflection data to map the submarine terraces, measure their depths, and estimate the amount of sediment cover. Hundreds of profiles drawn across these submerged terraces show that they are offset by as many as 10-15 m within the fault zone – almost twice the amount of onshore deformation from the earthquake 1100 years ago – and that the pattern of deformation is different on the east and west margins of Puget Sound.
Anna Pearson structure and tectonics
Exploring the Range of Possible Coupling Patterns on the Cascadia Subduction Zone
Locking models identify areas that are accumulating interseismic strain, highlighting the potential hazard due to a higher chance of rupture during the next coseismic period. Current locking models in Cascadia suffer from significant ambiguity, with many non-unique solutions that fit the available GNSS data. Additional uncertainty remains with regards to estimates of the updip and downdip limits of locking, along-strike variability, and to what extent different regions are fully locked. This also means that modeling a single output locking ratio is generally misleading, as it fails to communicate the uncertainty inherent within the model. This work uses a GNSS velocity field from the Pacific Northwest to calculate the interseismic slip deficit rate on the Cascadia Subduction Zone interface with an inverse problem, based on a set of algorithms defining the relationship between angular dislocations on a fault and associated surface deformation. Geodetic coupling is then calculated based on the ratio between the slip deficit and the velocity of plate convergence. We assess a variety of possible improvements to the basic locking model, including a Laplacian smoothing matrix with an associated regularization parameter and additional data used to improve the resolution of coupling patterns. We also consider the implementation of a method to define and communicate the range of solutions that fit the GNSS data, using a statistical sampling process to create a probability distribution of coupling coefficients for each element along the subduction zone interface. Here, we present preliminary results of our current locking model as well as future proposed refinements.
Madeleine Lucas structure and tectonics
Geometry of active Cascadia splay faults from CASIE21 seismic reflection imaging
Recent marine seismic reflection imaging of the Cascadia Subduction Zone shows evidence for recently active splay faults in the accretionary wedge that could slip during future megathrust earthquakes. Slip on splay faults during megathrust earthquakes increases vertical seafloor displacement and consequently tsunami size compared to slip on the megathrust fault due to the steeper dip angle of splay faults. Therefore, the potential for slip on splay faults in Cascadia poses an increased tsunami hazard to those living along the Cascadia coast. In this study, we use new CAscadia Seismic Imaging Experiment 2021 (CASIE21) multi-channel seismic (MCS) depth profiles to determine the three-dimensional geometries and locations of active splay faults in the Cascadia accretionary wedge. Splay fault geometries and locations determined from this study will be incorporated into earthquake and tsunami simulations of the Cascadia Subduction Zone as part of the Cascadia Coastlines and Peoples (CoPes) Hazards Research Hub in a broader effort to increase the resilience of coastal communities to Cascadia geohazards.
Jacqueline Silviria paleontology
Preliminary notes on mammalian diversity at the Constenius Locality (Paleocene, earliest Danian; Tullock Fm.), Williston Basin, Garfield County, Montana
The aftermath of the Cretaceous/Paleogene (K/Pg) mass extinction 66.051 Ma was characterized by the radiation of several mammal clades, particularly placentals, following the demise of non-avian dinosaurs. The lower Tullock Formation (Paleocene, earliest Danian) in the Williston Basin, northeastern Montana, harbors one of the highest-resolution records of post-K/Pg mammalian evolution globally. However, many historically and contextually important local faunas remain poorly described.
Here we highlight preliminary observations of mammal fossils from the Constenius Locality in eastern Garfield County, a Tullock sandstone channel cutting into underlying Hell Creek Formation mudstones. We have examined 130 specimens uncovered 2012-2021 by the Burke Museum of Natural History & Culture’s (UWBM) Hell Creek Project, through either surface collection in field or laboratory screen-washing and sorting of anthills and in situ sediment.
We provisionally allocate craniodental and mandibulodental specimens to species of multituberculate (Mesodma thompsoni = “M. garfieldensis”, Stygimys kuszmauli) and "archaic ungulate" placental (Oxyprimus erikseni, Mimatuta morgoth, Paleoungulatum hooleyi, Protungulatum donnae). Most species were previously identified from Constenius during expeditions by the University of California Museum of Paleontology (UCMP). Interestingly, we have yet to find some small taxa from penecontemporaneous localities (e.g., Procerberus, Prodiacodon, Thylacodon) among the UWBM screen-washed material.
The presence of P. donnae at Constenius reaffirms prior biochronological assignment to the Pu1 interval-zone of the Puercan North American Land Mammal Age (~66.05-65.80 Ma). This interval-zone is well known for its “disaster faunas” from the immediate aftermath of the K/Pg extinction.
Future fieldwork will focus on 1) further constraining the age of Constenius through paleomagnetic and radiometric dating and 2) expanding the sample size of mammalian fossils through collection of more anthills and sediment for screen-washing.
Tin-Yan (Jessie) So paleobiology
A Possible Earliest Occurrence of the Stem Primate Subfamily Microsyopinae at the middle Paleocene Mehling Site, Montana
In comparison to the abundance of research focusing on early Paleocene mammalian recovery from the K-Pg mass extinction, the mid-Paleocene (63-58 Ma) is an understudied period of mammalian evolution, particularly at the Mehling Site near Ekalaka, Montana. Previous work suggests this site dates to the mid-Paleocene, but its absolute age is not well established due to limited ash beds for radiometric dating. An isolated mammalian molar tooth specimen from the Mehling Site had been tentatively identified as Microsyopinae, a subfamily of an extinct clade of stem primates called Microsyopidae. However, the first appearance of Microsyopidae in the fossil record is during the late Paleocene (58-55 Ma). The purpose of this study is to investigate the incongruity between the taxonomic identification of this specimen and the age of the locality it was found in. I conducted a comparative analysis of the molar tooth specimen using fossil specimens, casts, and digital 3D models of the dentition of microsyopid mammals and their relatives in order to identify the specimen down to the finest taxonomic level possible. My preliminary results show that this specimen shares some features with Navajovius and Arctodontomys, two of the earliest possible genera of the Microsyopidae. The findings of this study will enhance our understanding of the origin of Microsyopidae and of this stage of mammalian evolution during the mid-Paleocene. If the specimen is confirmed to belong to the Microsyopidae and the geological age of the site is correct, then this fossil would push back the earliest occurrence of Microsyopidae in the fossil record to the mid-Paleocene, extending the temporal range of this clade by several million years. Ultimately, this knowledge informs our understanding of the origin and evolutionary history of stem primates.
Shay Rice geochemistry
Silicate Dissolution in Glacial Bedrock: Effects of Bacterial Spores and Geomicrobiological Implications
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.
Siti Rahayu Mat geochemistry
Discerning Fault vs Liquefaction Features Through Geomorphic and Isotopic Analysis in a Geothermal Setting, Dixie Valley, Nevada
Large-magnitude earthquakes commonly produce surface deformation, including meter-scale fault and liquefaction scarps. The size of a fault scarp is related to the magnitude of coseismic slip, but liquefaction scarps produced by near-surface slumping can vary in size regardless of magnitude. This study focuses on two subparallel scarps in Dixie Valley, Nevada. We hypothesize (1) liquefaction-related scarps are generated on sub-horizontal layers of loosely consolidated material, accompanied by evidence of lateral spread, subsidence, and low-temperature discharge, and (2) faults can produce scarps that transect topography and access high-temperature fluids. We used remote sensing and field data to describe the distribution of lateral spreading, subsidence, scarp profiles, travertine, and cemented alluvium. We constructed elevation profiles and cross-sections of the subsurface geology across the scarps. We collected travertine samples from calcite-cemented sands and hot springs and ran stable isotope analyses. We found the scarps to be about 9-15 m tall. Moderate flow rates (2-120 L/min) and hot spring temperature (23-49 °C) indicate a deep transect of the subsurface that reaches the heat reservoir (>1 km). Liquefaction features like compression zones and sand boils were not observed in the area. The range of δ13C of travertine is -1.73 to 3.10 ‰ VPDB and δ18O of travertine is -20.27 to -11.49 ‰ VPDB which falls in the ranges associated with thermogenic travertines. The decrease in δ18O composition corresponds to the sampling site with respect to hot spring surface temperature. The findings support the earthquake-related origin of these scarps. We interpreted the cemented sands to form from geothermally recharged water that flowed through the fault, mixed with meteoric water, explaining the presence of mollusk skeletal remains. The lack of geomorphic features related to liquefaction further supports faulting as the scarp origin. Mapping these features in geothermal settings provides a geological perspective for energy exploitation.
Katie Park geochemistry
Exploring Variability in S-Layer Protein Concentration in Response to Changes in Growth Conditions of a Deep Sea Hyperthermophilic Methanogen
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.
Eirini Poulaki volcanology/petrology
Apatite from the subduction seismogenic zone records a range of chemical and mechanical processes
Subduction zone deformation is intimately linked to dehydration reactions, fluid circulation, and chemical transformations. Apatite U-Pb petrochronology can resolve the timing of fluid infiltration and resultant deformation in the seismogenic zone because it readily deforms and recrystallizes under a specific range of P/T conditions, it has a closure temperature for Pb consistent with temperatures at the base of the subduction seismogenic zone, and it records chemical processes in its trace element geochemistry. We leveraged these characteristics for apatite and conducted microstructural analyses from blueschist and greenschist samples from an exhumed subduction complex on Andros Island, Greece. Both samples show several discrete deformation events and multiple styles of recrystallization. Preliminary results show the blueschist contains elongated apatite grains aligned parallel to the main foliation regardless of the textural setting. However, apatite grains within the mica-rich matrix are elongated with the c-axis parallel to foliation and preserve minimal internal lattice bending that we interpret as evidence of dissolution-reprecipitation creep. In contrast, apatite grains surrounded by radial chlorite and glaucophane deform through dislocation-accommodated deformation with lattice bending and low-angle subgrain boundaries and have random crystallographic orientations that might indicate micro-faulting, which could be related to strain hardening and localization of deformation. In the greenschist, syn-kinematic apatite grains within the chlorite matrix display no internal deformation, deforming by dislocation/precipitation creep, suggesting that chlorite facilitated increased fluid flow. Apatite grains between stronger minerals phases preserve multiple deformation mechanisms, with evidence of dislocation creep in portions of the grains in contact with the harder phases and strain-free euhedral potions of the grains in contact with the matrix. This work highlights that apatite may record different phases of fluid flow and deformation during subduction and we may be able to get chronologic and petrogenic constraints on the timing of fluid pulses and deformation from the subduction interface.
Yiyu Ni seismology
The Prototype of an Object Storage for Distributed Acoustic Sensing Data
Distributed Acoustic Sensing (DAS) is a new seismic observation method. It utilizes repeated laser pulses along optical fibers up to 100 km in length to measure changes in phase changes of backscattered light that occur due to rapid straining rate of the fiber. DAS dramatically expands the ability of dense seismic observation and has been used for detecting new tectonic faults and near-surface imaging. However, the huge amount of data generated by the DAS challenges the data I/O from both local computing clusters and data centers and limits the further processing. Commercial cloud environments are becoming more promising for such large-scale data processing, yet the current DAS data formats are not optimized for such tasks.
In this study, we propose a prototype of a data platform to host DAS data that employs an object storage service with cloud-optimized data formats. Specifically, we introduce MinIO to provide S3-compatible object storage and host DAS data in the Zarr and TileDB format. This framework is able to provide data to users across a research group or institutions, and has the potential to be used on the commercial cloud service (e.g., AWS S3). With container technique, little cost is required to deploy this platform on local machines.
Nicole Aikin dei
Boots on the Ground: Going Beyond Land Acknowledgements
Reshaping geoscience research requires a cultural shift away from extractive practices rooted in pervasive and self-perpetuating colonial and capitalist values and toward contextualizing place-based research and placing greater value on alternative ways of knowing. This shift cannot happen until individuals evaluate their role in histories of dispossession and settler-colonialism in regions where they work and live and how their institutions have harmed and continue to harm Indigenous people. Over the last decade, more universities, institutions, and individuals have adopted the practice of offering land acknowledgements. While this is an important and necessary step towards a vision of racial justice in the geosciences, land acknowledgements are not often backed up by concrete strategies for supporting Indigenous communities now and into the future. This presentation offers a road map and a successful example of how geoscientists can begin looking beyond land acknowledgements through facilitating strategic partnerships with in-network experts, Indigenous communities, community organizations and non-profits, and industry connections. As such, this presentation aims to encourage the geoscience community to reflect on their positionality, research the historical context that their institutions have had on local and Indigenous communities, and advocate for Indigenous peoples, their sovereignty and equitable research on their lands while working to build accountable and reciprocal relationships with current tribal members.
Jon Maurer glaciology
Upscaling of Existing Ground Penetrating Radar Surveys With Neural Networks in Temperate Glacial Environments
High elevation mountain glaciers are referred to as the “water towers of the world” due to their ability to store water internally and release it later through melt and runoff. Much of the work to understand these complex environments has focused on cold based polar glaciers in high latitude regions, neglecting temperate glaciers and associated snowpack which are more responsive than polar systems to minor climatic changes. Advancements in the availability of open source data, deep learning theory, and computational efficiency has opened up new methods of “data hungry” modeling that may be well suited to the type of complex terrain-climate interactions common in these environments. Through the use of regression based neural networks (NNs), this study explores the applicability of this method on a 400 MHz ground penetrating radar dataset collected on the Juneau Icefield between 2012 and 2021. The primary task of these networks is to find the statistical relationship between englacial layer thickness and a collection of topographic and climatological data with the goal of upscaling measurements from radar transects to the entire region. This task is approached using two different data structures, one that uses only a single year of data, and one that uses all available years of data. Models are validated using the standard “leave on glacier out (LOGO) and “leave one year out” (LOYO) holdout methods depending on the data structure. Through this method, realistic simulations of icefield scale snowpack distributions are generated and can be paired with existing models to output estimations of snow water equivalence.
Liam Kirkpatrick paleoclimate
Sensitivity of Denali Ice Core δ18O Record to Precipitation-Weighted Temperature
The climate of the North Pacific is highly sensitive to decadal scale climate oscillations with significant implications for global climate. Stable water isotope records in North Pacific ice cores present a promising method to constrain the history of regional climate variability through the holocene, given their sensitivity to temperature and regional weather patterns. However, existing interpretations of North Pacific ice core stable water isotope records are varied and contradictory. Here, we examine the stable water isotope record from the Denali Ice Cores. The high temporal resolution and accurate timescale of this ice core allows for an unprecedented seasonal examination of the water isotope record. We employ comparison with reanalysis datasets and HYSPLIT back trajectory modeling to demonstrate the importance of seasonality in driving the North Pacific water isotope record. We find that the δ18O record is highly correlated with precipitation-weighed temperature on annual timescales. In the summer, this correlation is dominated by a simple temperature relationship, as precipitation-weighted temperature is not meaningfully different to average temperature. However, in winter months, Aleutian Low-driven storm systems result in seasonal precipitation weighted temperature being significantly warmer than average temperature. Therefore, the Denali Ice Core water isotope record cannot be viewed as a simple temperature proxy. These results reconcile prior North Pacific stable water isotope interpretations, and highlight the need for consideration of seasonal changes in the interpretation of these records.
Glaciology 1 (9:00am - 10:00am)
Benjamin Hills
Radar-inferred crystal fabric at Hercules Dome supports divide stability since the last glacial maximum
Hercules Dome is a prospective ice-core drilling site due to its location at the bottleneck between East and West Antarctica. If ice from the last interglacial period, ~120 thousand years ago, has been preserved in the deep ice sheet at Hercules Dome, it could provide critical insight on the history of the West Antarctic ice sheet during that time in which the global climate was most recently similar to today. The likelihood of interglacial ice preservation depends on the ice-flow stability at Hercules Dome and its persistence as a divide between the Ross and Ronne Ice Shelves. Ice-sheet models show Hercules Dome divide migration by 10’s of kilometers, even since the last glacial maximum, ~14 thousand years ago. Here, we constrain ice-flow history at Hercules Dome using radar measurements of crystal orientation fabric (COF). COF develops over time as a result of cumulative strain, so it depends on both the nature of ice flow and the time over which that flow has been consistent. We also use a physical model to simulate COF development for both constant strain (stable divide) and variable strain (divide migration) scenarios. We find that Hercules Dome has been stable in its current ice-flow configuration, at least since the last glacial maximum. Divide stability has likely been due to a prominent bedrock ridge which had not been surveyed until now and was therefore not represented in the modeled bed geometry.
Daniel Otto
Assessing the attribution of alpine glacier mass loss to anthropogenic warming over the last millennium using ensemble paleoclimate reconstructions and GCM simulations
The central estimate of the Intergovernmental Panel on Climate Change is that the magnitude of anthropogenic warming since 1850 is equal to 100% of the observed warming. However, the IPCC is notably much more timid in attributing glacier mass loss to anthropogenic warming over the same period. Disagreements have arisen in previous research, primarily stemming from ambiguity in the dynamic disequilibrium of preindustrial glaciers and its lingering effects. Accounting for variability in glacier disequilibrium entering the industrial era, Roe et al., (2021) used simple glacier models and synthetic climate scenarios to estimate a mass-loss attribution of ˜100% [90-130%, likely range] over the full industrial era. Our work further assesses this claim for a case study of glaciers in North America and the Alps using: i) realistic ice dynamics, ii) observed glacier geometries, iii) ensembles of last-millennium reconstructions (LMR) and GCM simulations, and iv) a comprehensive sensitivity and uncertainty analysis. In addition to CMIP6 past1000 simulations, we use recently developed LMR paleoclimate reconstructions, specifically adapted for melt-season temperatures. By using millennial-scale climate time series, we avoid the need for an accurate initial condition. We simulate glacier mass-balance and length fluctuations over the last millennium for a variety of potential climate histories to produce an uncertainty envelope for each glacier’s preindustrial state. For our case-study of glaciers, we find that all: i) exhibited slow growth over the last millennium, ii) have lost mass over the industrial era, and that iii) the magnitude of industrial-era mass loss for each glacier greatly exceeds natural variability over the last millennium. Given that 100% of industrial-era temperature change is attributable to anthropogenic activity, these results imply that mass loss for these glaciers can be confidently attributed to anthropogenic warming since the beginning of the industrial era (1850 vs. the IPCC’s 1990). Work is ongoing to expand the analysis scope to a larger network of well-observed glaciers, with potential for a global assessment in the future.
John-Morgan Manos
Using Optical Fiber for Ice Borehole Thermometry
Measuring temperature profiles of glacial ice is critical in determining ice rheology, understanding basal ice conditions, and inferring paleoclimate. However, glacier and ice sheet temperature profiles are often limited by low spatial or temporal resolution limited by the spacing between thermistors and their relatively high thermal mass. In this study, we deployed a multimode optical fiber in the CMC1 borehole at Allan Hills, Antarctica and sampled it with a Distributed Temperature Sensing (DTS) interrogator. DTS sends laser pulses through the optical fiber and utilizes the intensity ratio between the Raman backscattered Stokes and anti-Stokes photons to measure temperature spatially resolved along the optical fiber. We collected temperature profiles in the 155m deep borehole from the ice surface to the bed with 25.6 cm vertical resolution - orders of magnitude better than conventional borehole temperature profiling methods. Due to its low thermal mass, the fiber equilibrated fast to ice temperatures, allowing for relative temperature resolutions better than 0.05K. We found a clear seasonal temperature signal within the top 15-20 m of the ice column and a linear warming trend to the bed consistent with the geothermal flux. On top of that the high spatial and temperature resolution of DTS reveals localized temperature anomalies and second order deviations from the linear warming trend towards the bed that are not captured by thermistor measurements in the identical borehole. With this, our study demonstrates the feasibility of DTS in Antarctic environments and the potential for use in deep ice boreholes in the future.
Marguerite Shaya
Preliminary polarimetric radar results from the Allan Hills, Antarctica
At the Allan Hills blue ice area in Antarctica, wind scour and sublimation drive surface mass loss, while steep bedrock topography cause the uplifting of ancient ice towards the surface. Shallow ice-coring expeditions in the region have discovered discontinuous outcroppings of ice that range in age from 1 Ma (million years ago) to around 4 Ma. Because this ice has the potential to transform our understanding of greenhouse gas concentrations during critical periods of Earth’s climate history, the Center for Oldest Ice Exploration (COLDEX) is committed to drilling more shallow ice cores and, if logistically possible, an intermediate depth ice core at the Allan Hills. Interpreting these ice cores, however, presents a challenge because of the folding and discontinuities present in the ice. Furthermore, flowlines may have changed over the past several million years, making it unclear whether ice from different cores originated in the same place. In order to gain as much knowledge as possible from the Allan Hills ice cores, an understanding of the past and present flow regime in the area is required. To this end, during the 22/23 Antarctic field season, a team of COLDEX researchers collected 26 polarimetric ApRES (autonomous phase-sensitive radar echo sounder) acquisitions from around the Allan Hills. Polarimetric radar is developing as a tool to measure the net orientation of anisotropic ice crystals, termed the ice fabric. Because ice crystals preferentially align based on the principal stresses they are subjected to, the ice fabric contains information about the past and current ice flow regimes. Here we present the 22/23 polarimetric ApRES data from the Allan Hills, and discuss the implications of this data towards ice fabric in the region and towards COLDEX ice coring efforts.
Glaciology 2 (10:15am - 11:15am)
Simon Hans Edasi
Estimating Non-Ice Sheet Glacier Volume Without Physics
Several estimates of global non-ice sheet glacier volume have been presented in the literature. These studies commonly rely on simplified physical models of ice flow. Here, we propose a completely data driven approach. We carry out a regression analysis to estimate the glacier thickness measurements from the Glacier Thickness Database (GlaThiDa; Gärtner-Roer et al., 2014) using the physical attributes from Randolph Glacier Inventory (RGI; Pfeffer et al. 2014) as independent variables. This regression analysis is carried out using a shallow neural network with dropout layers to avoid overfitting (Erichson et al. 2020). We use bootstrap aggregation to quantify uncertainties associated with the choice of training data set and the choice of model architecture. We then compare our global thickness distribution with previously published estimates in Farinotti et al. (2019) and Millan et al. (2022) using the Z-test. Although the 1-sigma uncertainty bars overlap for each of these estimates, the Z-test finds statistically significant differences between the various estimates because the underlying sample size is so large. We find that studies that involve physics-based assumptions estimate a greater global volume of glacier ice. We interpret this discrepancy as a reflection of the sparsity of detailed in-situ observations facing efforts to estimate global ice mass.
Dominik Graeff
Distributed Subsea Fiber-Optical Sensing along the Calving Front of a Greenlandic Tidewater Glacier
Calving fronts of Greenland’s tidewater outlet glaciers are the nexus where atmospheric and oceanic forcings on the cryosphere condense. Dynamic processes acting on these calving fronts not only impact future tidewater glacier evolution but control the stability of the Greenland Ice Sheet. Rapid changes in these processes caused by global warming potentially result in the partial disintegration of the ice sheet with imminent environmental and socio-economic consequences on regional and global scales.
To study these physical processes in their entirety, we use a never-before possible geophysical approach. In summer 2023, we will install a subsea fiber-optic cable across a Greenlandic fjord on the seafloor and parallel to the calving front of a tidewater outlet glacier. We will use the optical fiber itself as a sensor by measuring tiny changes of strain in the cable over time scales reaching from milli-seconds to years with Distributed Acoustic-, Temperature-, and Strain- Sensing (DTS, DAS, DSS). By doing so, we can utilize the 7km long cable as 1’500 seismometers, 30’000 thermometers and 7’000 strain-meters distributed along the calving front. With this immense data set, we aim to spatio-temporally resolve and quantify: 1) aerial and underwater iceberg calving, 2) warm oceanic water intrusions at the seafloor, 3) meltwater plume activity, 4) underwater ice melt, 4) fjord water stratification and 5) mixing as well as subglacial discharge, 6) sedimentation and 7) frictional resistance at the glacier bed. All together these measurements will create a yet unresolved picture of dynamic processes at calving fronts.
Stephanie Olinger
Ambient Noise Correlation of Glacier Borehole DAS Data
Interferometry of the ambient seismic wavefield can reveal the perturbations in wave speeds through time that arise within a dynamic subsurface. In the near surface solid earth, wave speeds change in response to fluctuations in a wide range of material properties including soil saturation, temperature, and compaction. In glaciers, ice fabric, crystal grain orientation, temperature, and flow rate may influence seismic wave speeds. Here, we perform ambient noise cross correlation using distributed acoustic sensing (DAS) data recorded over three days by the first glacier borehole DAS deployment, located at the Store Glacier in West Greenland. We use the resulting correlation functions to infer variation in glacier ice properties, which we relate to the glacier dynamics present at the Store Glacier.
An Li
An investigation of alcoves in the northern mid-latitudes of Mars as potential evidence of past glaciations
While glaciation on Mars is typically considered to be cold-based, recent work suggests more widespread wet-based glaciation than previously expected. On Earth, glacial cirque erosion requires liquid water at the base of the glacier. Cirques are typically characterized by a concave basin connected to a steep headwall and are expected to form from depressions in mountain sides that fill with snow/ice and over time support active glaciers that deepen the depressions by wet-based glacial erosion. While select alcoves have been interpreted as cirques in multiple locations on Mars, we assess a large-scale population of alcoves as potential cirques across Deuteronilus Mensae (40-48ºN, 16-35ºE), a region in the mid-latitudes of Mars characterized by mesas encompassed by glacial relicts from previous glaciations. Excluding alcoves filled with mapped icy glacier-like forms, we map a total of 1952 alcoves using Context Camera images and High Resolution Stereo Camera digital elevation models. We apply the Automated Cirque Metric Extraction tool (Spagnolo et al. 2017) in ArcMap to calculate 16 metrics such as length (L), width (W), elongation (L/W), depth (H), area, elevation, and aspect. To evaluate alcoves shaped by glacial versus non-glacial processes, we define seven classes of alcoves but focus on only the simple class, which are independent alcoves with a distinct headwall and sidewalls. We also use High Resolution Stereo Imaging Science Experiment imagery to examine ice-related features within the alcoves, such as moraines and paraglacial terrain. We refine our dataset to potential cirques by retaining only simple alcoves with a ratio of L/W between 0.5-4.25 and W/H and L/H ratios between 1.5-4.0, which correspond to cirques mostly eroded by ice-action on Earth. We find a preferential southeastward aspect and that ~18% of alcoves are within 10 km of a GLF. We differentiate the alcoves most likely influenced by glacial erosion, thus expanding previous knowledge on the extent and type of glaciation styles present in Deuteronilus Mensae.
DEI & Outreach and Education (11:30am - 12:15pm)
Brody Hovatter
The Discoveries in Geosciences (DIG) Field School: connecting teachers with researchers and museums to inspire students with real science in the classroom
The Discoveries in Geosciences (DIG) Field School is a non-profit, professional development program for K-12 teachers created by University of Washington Burke Museum paleontologists. The mission of the DIG is to connect K-12 STEM (Science, Technology, Engineering, and Math) teachers with scientific research, scientists, and museums through ongoing training in paleontology and geology and related curricula for their classrooms. The program began in 2010 with seven local Montana teachers and has since served over 250 teachers from 33 states, South Korea, and Canada and reached over 25,000 students.
Central to the DIG is a four-day, hands-on, immersive field experience for teachers at an active research site in the Hell Creek badlands of northeastern Montana. Teachers are instructed in and engage in paleontology and geology activities that directly contribute to our field research while simultaneously drawing connections between the ongoing research on the Cretaceous-Paleogene mass extinction and relevant cross-cutting concepts and scientific practices of the Next Generation Science Standards (NGSS). The field school is the capstone experience of the DIG, but the program extends beyond the time spent in the field by providing teachers ongoing educational support throughout the school year. We do this through a variety of methods including specialized curriculum development and education tools (e.g., our traveling “museum in a box”), online lesson plans that implement the current NGSS, and classroom and museum visits. Further, these educational resources provide authentic community science opportunities for classrooms whereby they help collect and analyze data that contribute to our active research and become permanent records in the Burke Museum of Natural History and Culture vertebrate paleontology collection. As such, the DIG has grown into an effective model for combining scientific research and museum resources to provide a powerful educational outreach program for promoting science as a process among teachers and their classrooms.
Madeleine Lucas
STEM Alternative Spring Break: Teaching geology at the Quileute Tribal School in La Push, WA
This spring break, I will be traveling to La Push, Washington on the Olympic Peninsula to teach to high schoolers at the Quileute Tribal School (QTS) for a week through the UW STEM Alternative Spring Break Program. During winter quarter, I have been leading a team of UW students (ESS grad Vero Elgueta and CS undergrad Mya Baker) to develop curriculum that focuses on applying culturally-sustaining and place-based pedagogy that will enable us to learn with Quileute students about the geology where they live. In our lessons, we emphasis the value of Quileute tribal knowledge in understanding the Earth and the coastal lands of the Pacific Northwest which the Quileute people have inhabited since time immemorial. We will teach the students how to make geologic observations through the lens of their identities as indigenous peoples and empower Quileute high schoolers to pursue STEAM pathways after graduation. I will highlight what we teach them in this talk, but more importantly, what they teach us.
Spotlight Poster
Nicole Aikin
Boots on the Ground: Going Beyond Land Acknowledgements
Reshaping geoscience research requires a cultural shift away from extractive practices rooted in pervasive and self-perpetuating colonial and capitalist values and toward contextualizing place-based research and placing greater value on alternative ways of knowing. This shift cannot happen until individuals evaluate their role in histories of dispossession and settler-colonialism in regions where they work and live and how their institutions have harmed and continue to harm Indigenous people. Over the last decade, more universities, institutions, and individuals have adopted the practice of offering land acknowledgements. While this is an important and necessary step towards a vision of racial justice in the geosciences, land acknowledgements are not often backed up by concrete strategies for supporting Indigenous communities now and into the future. This presentation offers a road map and a successful example of how geoscientists can begin looking beyond land acknowledgements through facilitating strategic partnerships with in-network experts, Indigenous communities, community organizations and non-profits, and industry connections. As such, this presentation aims to encourage the geoscience community to reflect on their positionality, research the historical context that their institutions have had on local and Indigenous communities, and advocate for Indigenous peoples, their sovereignty and equitable research on their lands while working to build accountable and reciprocal relationships with current tribal members.
Geomorphology (1:45pm - 3:00pm)
GeoClub Grand Canyon Spring Break Presentation
GeoClub takes the Grand Canyon
The students of GeoClub present their experiences and the value of fieldwork during the week long spring break trip to the Grand Canyon.
Susannah Morey withdrawn
The legacy of megaflood-deposited boulders on river processess and form
The role of high-magnitude, low-frequency floods in shaping landscapes on Earth and other solar system bodies is an outstanding question in geomorphology. On Earth, glacial lake outburst floods, including exceptionally large megafloods (discharge ≥106 m3/s), carve canyons, mobilize large boulders, and initiate landslides, but the legacy of megaflood deposits on subsequent river evolution remains underexplored. Here, we present a numerical model that tests the impact of outsized (those that exceed the expected stream competence), megaflood-deposited boulders on bedrock fluvial processes and form. We build on a previous 1D reach-scale model that uses a shear stress bedrock erosion rule to simulate the evolution of boulder-influenced bedrock rivers. This model accounts for two key effects of immobile boulders in the channel: bed armoring and hydraulic roughness/drag that reduces erosive stresses on the bed. We extend this model to simulate a full longitudinal river profile as it evolves after a megaflood-boulder depositional event. Model runs are inspired by the Yarlung-Siang River (YSR) in the eastern Himalaya, which hosts dozens of boulder bars that previous hydraulic simulations suggest were deposited during outburst floods. Simulated megaflood bed shear stresses can move boulders ≥4 meters in diameter that are immobile in subsequent, smaller discharge flows, and, thus, become semi-permanent fixtures in the modern landscape. We therefore modify the model to include large (≥4 m) megaflood-derived blocks, with sizes and longitudinal positions scaled to measurements of in-channel boulder bars along the YSR. The initial river profile is concave-up, has a constant channel width and uplift rate, and a monsoon influenced discharge distribution scaled to the YSR. We track bed elevation, erosion rate, and the number and size of boulders along the river profile. Results suggest that megaflood-deposited boulders impede bedrock erosion, creating knickpoints where they are deposited. This causes a decrease in erosion rates in the upstream reaches of the river. The spatial distribution of megaflood-deposited boulders likely influences average channel steepness in the river profile. These results suggest an important legacy of megaflood deposition on channel processes and form in highly erosive, steep mountain rivers.
Paul Morgan
Estimating landslide dam susceptibility along Oregon Coast Range rivers
Large earthquakes and significant storms can initiate a chain of cascading hazards by triggering of widespread hillslope mass failures, including the formation of landslide dams. Landslide dams pose a unique threat due to their potential to lead to more hazard through catastrophic outburst floods. To better prepare for these hazards, we need to anticipate where landslides are likely to dam rivers by identifying the most vulnerable river valleys and hillslopes. We target the Oregon Coast Range, where landslide dams have formed in the past and have great potential to form in the future. We use the Morphological Obstruction Index (MOI), which is the ratio of valley width to landslide volume, to estimate regions of high vulnerability for dam formation within our study area. First, we attempt to calibrate the MOI with a local landslide dam database. We then calculate the valley widths using a threshold-based metric. Finally, we estimate the probability that a landslide would be big enough to dam that section of the river using locally derived landslide volume frequency distributions for a range of sediment volume scenarios. The ultimate goal of this research combines this measure of “damability” of a river stretch with the likelihood of nearby slope failures to produce maps estimating where landslide dams will most likely form. We anticipate our results to be of use to communities planning for the management of and evacuation from widespread hazard events that trigger widespread landslides in coastal Cascadia, such as earthquakes and storms
Tamara Aranguiz
Role of sediment and climate variability in strike-slip fault arid landscapes
Strike-slip faults show some of the most ubiquitous evidence of activity in the geomorphic record. Field-based observations and numerical models of lateral faults indicate that preservation of offset geomarkers depends on fault slip rates and surface erosional activity. Desert environments, on the end of the climate spectrum, are sensitive to climate changes and tend to provide an excellent record of landscape modification. Despite the great record that deserts offer, the interaction between lateral faulting and surface processes has been poorly studied. Drainage patterns in the Salar Grande, a hyperarid intermountain basin in the Atacama Desert, Northern Chile, show perturbations resulting from dextral fault activity. Yet, the rates of tectonic processes and climate variability on the landscape are not well understood. Based on these observations, we use a landscape evolution model (LEM) to explore the influence of intermittent wet periods on the topographic response of a hyperarid landscape that is offset by a right-lateral strike-slip fault. We use a set of open-source tools from Landlab (a Python-based modeling environment) to create a synthetic landscape whose topography is formed by two layers, soil on top of bedrock. Model experiments are conducted with: 1) long periods of total absence of fluvial activity; 2) a constant rate of lateral slip, hillslope activity and regional uplift; 3) brief humid episodes represented by flow routing and channel erosion. A series of controlled experiments test the influence of the duration of fluvial activity episodes, fault slip rate, and surface process efficiency. Hyperarid intervals lasting up to several millennia allow for tectonic offset without fluvial modification of channels. When surface processes “re-awaken” during wetter periods, they inherit a tectonically altered topography with fault-generated depressions and scarps that will determine the sediment infill-incision cycle. Our findings shed light on the control that tectonics exert over erosional processes in arid regions in general and contribute to quantifying the impact of lateral faulting on Earth surface dynamics.
Keynote Address: 3:30 PM - 4:50 PM (JHN 102)
Guest Speaker : Bretwood Higman
Lessons of Cassandra: Geohazard Mitigation and Climate Uncertainty
Are geohazard scientists modern day Cassandras -- cursed to predict disasters but unable to mitigate them? Thousands of scientists have spent their careers surveying the grim aftermath of giant tsunamis, sending mud flows through giant flumes, and building computer models to predict how the next earthquake will unfold. Hundreds of millions of dollars and many decades later, our understanding is better than ever. However, despite this progress, recent disasters look more like tragic missed opportunities than scientific triumphs. In Alaska, we are grappling with the emergence of large paraglacial landslides that may be increasing dramatically with climate change. I lay out examples of real world hazard mitigation efforts from subduction zone earthquakes and the recent Tonga eruption. These include obscure clues with significance that was only recognized too late, huge public investments that failed to protect, as well as communities that responded quickly and effectively to disaster. I’ll lay out questions researchers and community stakeholders in Alaska are asking about paraglacial landslide hazards, and how we hope we can do better. What is needed to get ahead of the next climate disaster?
Astrobiology (9:00am - 10:30am)
Andrew Shumway
Don’t Be Salty: How Martian Regolith Suppresses Salt Crystallization, Allowing Liquid Water to Persist at Much Drier Conditions Than Previously Thought Possible
Brines affect the geochemistry and habitability of Mars’ surface and are central to astrobiological investigations of the planet. Despite extensive research on pure brines, realistic mixtures of brines in Martian regolith are relatively poorly studied. In this work, we predict the water content of ideal mixtures of brine + regolith at various conditions, then compare to measurements of actual brine-regolith mixtures in the lab. We find that real mixtures exhibit unique, non-ideal behavior, and so must be studied independently of the two endmembers. Most notably, we demonstrate that regolith suppresses salt crystallization over a wide range of Mars-relevant temperatures, relative humidities, and salt concentrations. This finding has significant implications for astrobiology, geochemistry, and geomorphology on Mars because it suggests that liquid water can persist in briny regolith at drier conditions than previously thought possible. By suppressing salt precipitation, regolith improves brine habitability by removing a hazard to life (crystallization) and preventing H2O from becoming locked away in a form that is inaccessible to life (hydrated salt). This informs planetary protection considerations and the search for life on Mars by expanding the physical and temporal extent of potentially-habitable liquid brines in the regolith. The results may also explain observations of high soil cohesivity and mobilized ions dispersed through the soil.
Kimberly Sinclair
Mineralogy of Evaporites and Sediments in the Alkaline Phosphate Rich Lakes of the Cariboo Plateau
Last Chance and Goodenough Lakes, located in the Cariboo Plateau of British Columbia, are potentially the most phosphate rich lakes in the world, with previous studies showing up to 40 mM PO43- [1]. Studying phosphate rich lakes is significant for origin of life research, as phosphate is essential for prebiotic synthesis of nucleic acids and other vital components. Prebiotic phosphorylation experiments require high concentrations (~1 M) of phosphate in order to incorporate phosphate into biomolecules, yet in most natural environments, phosphate concentrations are much smaller (~10^-6 M) due to phosphate precipitation with calcium as apatite minerals. As Toner & Catling [2] propose, carbonate rich lakes could be a solution to this ‘phosphorous problem’ [3], because in the presence of high concentrations of carbonate, calcium may instead precipitate with carbonate, leaving phosphate in solution. We tested this hypothesis by studying the evaporites found on the lakeshore of carbonate and phosphate rich Last Chance and Goodenough Lakes and looking for the presence of apatite minerals or calcium carbonate minerals. We collected evaporite and sediment samples over 3 field seasons at Last Chance and Goodenough Lakes in November 2021, June 2022, and September 2022. Samples were chosen at a variety of locations around both lakes, ranging from the spring water source to the middle of each lake. Samples were also collected that looked morphologically unique or had distinct pigmentation. The mineralogy of the precipitates in the lake sediments as well as the lakeshore evaporites were characterized by X-ray diffraction. We found an absence of phosphate minerals in any of the precipitates, but an abundance of sodium carbonates in the evaporites and sediments, as well as calcium carbonates in the form of dolomite in only the sediments. These results are consistent with the hypothesis that calcium carbonates precipitate early in the mineralization sequence, decreasing dissolved calcium concentrations and allowing phosphate to accumulate to high concentrations instead of precipitating out as apatite.
[1] Hirst, J.F. (1995) (Master’s Thesis, University of Saskatchewan, Saskatoon, Canada)
[2] Toner, J.D. and Catling, D.C. (2020), PNAS, 117 (2) 883-888.
[3] Schwartz, A.W. (2006), Phil. Trans. R. Soc. B 361:1743–1749
Ping-Chun Lin
The Rare Earth Element Distribution in Marine Carbonates as a Potential Proxy for Seawater pH on Early Earth: A Proof of Concept
Understanding the marine environment of early Earth is crucial for understanding the evolution of climate and early life. However, the master variable of Archean and Proterozoic seawater, the pH, is poorly constrained, and published ideas about the pH range encompass ~7 pH units from mildly acidic to hyperalkaline. To better infer ancient seawater pH, we examine the possibility of a seawater pH proxy using rare earth elements (REEs) in marine carbonates. The principle is based on an increased enrichment of heavy relative to light REEs with decreasing pH due to REE complexation and scavenging into carbonate. We calibrated such an REE pH proxy using pH variability in modern seawater in the Pacific and tested the proxy with REE measurements from multiple carbonate formations over time. We validated our REE-seawater pH proxy by comparing REE-pH estimates to published pH estimates of Cenozoic and Neoproterozoic seawater that use the established pH proxy of boron isotopes (δ11B). REE-pH estimates roughly agree with the Cenozoic and the Ediacaran δ11B-pH proxy. The uncertainty in our REE-pH proxy can be explained by noise from freshwater influence, siliciclastic input, and diagenesis. This proof-of-concept study demonstrates that the REE-pH method provides pH estimates with an accuracy of 1.5 in the range of pH=6.0-9.0, arguably sufficient to resolve the debate about acidic versus alkaline Precambrian seawater and better understand the coevolution of life and early Earth’s environment. Future work includes identifying diagenetic alteration in Proterozoic and Archean marine carbonate samples and developing a screening protocol for sample sets to produce a time series of seawater pH estimates.
Trent Thomas
The 4 Billion Year History of Mars’s Atmosphere Revealed by Isotopic Evolution Models
There is abundant mineralogical and morphological evidence that liquid water was present on the surface of ancient Mars. Considering that modern Mars is cold and dry, how did ancient Mars support this water? How and why did Mars evolve to the drastically different modern state?
We address these questions by analyzing the information recorded in the isotopic composition of Mars’s atmosphere. Processes that shape Mars’s atmosphere on long timescales (e.g., atmospheric escape, volcanic outgassing) have distinct impacts on the size and isotopic composition of the atmosphere. We model the evolution of Mars’s atmosphere over 4 billion years according to our theoretical and empirical understanding of these planetary processes, focusing on the three most abundant species in modern Mars’s atmosphere: CO2, N2, and Ar.
We identify a range of potential atmospheric evolution scenarios that simultaneously reproduce the modern pressure and isotopic composition of the modern atmosphere. With these scenarios, we place quantitative constraints on the ancient size and composition of the atmosphere, and how it evolved to the modern state. The results presented here provide important geologic context for investigating the surface conditions on ancient Mars: the only non-Earth environment in the history of the solar system with evidence for long-lived surface liquid water.
Nick Wogan
Rapid Timescale for an Oxic Transition During the Great Oxidation Event (GOE) and the Instability of Low Atmospheric O2
Understanding the ~2.4-2.1 Ga rise of atmospheric oxygen on Earth is important for assessing precursors to complex life and for evaluating potential future detections of oxygen on exoplanets as signs of extraterrestrial biospheres. However, it is unclear whether Earth's initial rise of O2 was monotonic or oscillatory, and geologic evidence poorly constrains O2 in the “boring billion” afterwards, 1.8 to 0.8 billion years ago. Here, we used a novel time-dependent photochemical model to simulate oxygen's rise and the stability of subsequent O2 levels to perturbations in supply and loss. When forced with stepwise changes in biogenic fluxes, transitions between anoxic and oxic atmospheres take between only 10^2 and 10^5 years. Results also suggest that O2 between ~ 10^-8 and ~ 10^-4 mixing ratio is unstable to plausible atmospheric perturbations. For example, when atmospheres with these O2 concentrations experience fractional variations in the surface CH4 flux comparable to those caused by modern Milankovitch cycling, oxygen fluctuates between anoxic (~10^-8) and oxic (~10^-4) mixing ratios. Overall, our simulations are consistent with possible geologic evidence of unstable atmospheric O2, after initial oxygenation, which could occasionally collapse from changes in biospheric or volcanic fluxes. Additionally, modeling favors mid-Proterozoic O2 exceeding 10^-4 - 10^-3 mixing ratio, otherwise O2 would periodically fall below 10^-7 mixing ratio, which would be inconsistent with post-GOE absence of sulfur isotope mass-independent fractionation.
Upgoer 5 (10:45am - 11:41am)
Trent Thomas
Big changes on the red space rock next door
Tamara Aranguiz
Side-Fault Dance.
Field-based observations and numerical models of strike-slip faults indicate that the regional footprint and preservation of the landscape response depends on fault slip rates, climatic conditions, and surface erosional activity. Arid desert environments, on one end of the climate spectrum, are especially sensitive to climate changes and tend to provide an excellent record of fault-slip histories and landscape modification in response to faulting. For example, the Salar Grande strike-slip fault slips at slow to moderate rates (~1 mm/yr) across the Atacama Desert of Chile and is characterized by long periods of hyper aridity with the absence of fluvial activity, but still preserves dextral offset geomarkers evidencing past humid periods and faulting. On the other extreme, wet environments are intensively affected by constant fluvial erosion and mass wasting. In New Zealand, for example, complex systems of parallel right-lateral faults in the Tararua Mountains, North Island, interact with each other with neighboring rivers flowing across and along fault branches that slip at different rates (< 1 mm/yr to > 10 mm/yr) and juxtapose different scale high-relief topography (shutter ridges). Inspired by the complexities of these real-world contrasting strike-slip fault settings, we create analog numerical simulations in Landlab to observe the role of climate variability, sediment, and the interaction between multiple structures affecting the topography. Model results are compared with field observations, focusing on channels, ridges, and mountain range scale observations.
Jess Ghent
I'm just a girl, standing in front of a boy, asking him to help her find the world's anger bursts so people don't die
The eruption of Hunga Tonga-Hunga Ha’apai (HTHH) on 15 January 2022 generated a series of tsunamis that crossed the Pacific basin. Given that ocean-spanning tsunami models are largely designed around earthquake source mechanisms, traditional warning systems were ill-equipped to accurately forecast the arrival times, showing the need for a holistic approach to tsunami monitoring. It is well established that the ionosphere, an electrically charged layer of Earth’s atmosphere, registers acoustic-gravity waves produced in natural events as perturbations to ions within this layer. These Traveling Ionospheric Disturbances (TIDs) offer valuable information about atmospheric and oceanic behavior during eruptions, earthquakes, and tsunamis in areas where conventional monitoring tools are not available. By performing spectral analyses on Global Navigation Satellite Systems (GNSS) data over the southwest Pacific during the Tonga event, we have shown that the tsunami’s gravity waves can be isolated from the eruption’s acoustic waves within the TIDs. This ionospheric phase separation provides the basis of continued work alongside NASA’s Jet Propulsion Laboratory, with whom we are working toward an operational, real-time, global geohazard monitoring network built upon GNSS-derived TIDs. Our future work within this project will see us exploring whether observations from Tonga hold true for other tsunami events and whether the isolated tsunami phase can act as a trigger to warn of incoming tsunamis.
Daniel Otto withdrawn
Considering how fast up-high ice blocks have disappeared and if it is the fault of human-caused warming over the last ten hundred years using pictures of how hot or cold the air could have been.
Amanda Syamsul
How can heavy things on the ground cause shaking around the world?
The ground we stand on is broken into parts that fit together. These parts of the ground moving up, down, or to the side, is the number one reason why ground shaking happens. But other things can also make shaking happen — like having heavy things on the ground. Things like having a lot or a little rain, ice pieces turning into water (or the other way around), or having water in empty ground spaces, can make the ground heavier or lighter. In this study, we looked at changes in the world's water, ice, and snow, to see how it might change the chance of the ground shaking happening. This has been studied by other people before, but only for a short time, or only in some parts of the world. What makes our study a little different is that we look at all the big ground shakes that happen through a long time. Since not all places in the world have a lot of ice pieces or get a lot of rain, this also means that the ground can be heavier or lighter for different reasons, so we also consider these different reasons. The two things we needed to know for this study were: 1) all the big ground shakes from the past 20 years, taken from people who keep track of where they happened and how much shaking there was and 2) something in space that tells us how much water is on the ground at different places on our World Ball, at different times. With these two things, we figured out the chance of shaking happening when the ground is heavier or lighter. We found that when heavy things are put on or taken off the ground, ground shaking has a higher chance of happening. This was true even when we took out some shakes that were too close to each other. We took out these shakes using two different ways, both made by people who have studied shakes for a long time. What we found is really cool because it helps us think about how one kind of change in our World Ball can lead to another change in our World Ball. Think about it this way: thanks to huge ground shakes in the past, we know that ground shaking can cause less strong parts of the land to slip. Since land slipping can change how heavy the ground is, our study suggests that land slipping could also cause ground shaking. Our study fills in a little space in the many things we now know about how the ground being heavy can tie into ground shaking.
Simon Hans Edasi
A new guess for how much ice is in the world
Nicole Aikin
What if you're a little bit of land that learned to stand tall and strong?