Scholarly Works, Geosciences

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Research articles, presentations, and other scholarship


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  • A Machine Learning Approach to Flood Depth and Extent Detection Using Sentinel 1A/B Synthetic Aperture Radar
    Tiampo, K.; Woods, C.; Huang, L.; Sharma, P.; Chen, Z.; Kar, B.; Bausch, D.; Simmons, C.; Estrada, R.; Willis, Michael J.; Glasscoe, M. (IEEE, 2021-01-01)
    The rising number of flooding events combined with increased urbanization is contributing to significant economic losses due to damages to structures and infrastructures. Here we present a method for producing all weather maps of flood inundation using a combination of synthetic aperture radar (SAR) remote sensing data and machine learning methods that can be used to provide information on the evolution of flood hazards to DisasterAware©, a global alerting system, that is used to disseminate flood risk information to stakeholders across the globe. While these efforts are still in development, a case study is presented for the major flood event associated with Hurricane Harvey and associated floods that impacted Houston, TX in August of 2017.
  • 'Boundary': mapping and visualizing climatically changed landscapes at Kaskawulsh Glacier and Kluane Lake, Yukon
    Shugar, D. H.; Colorado, K. A.; Clague, J. J.; Willis, Michael J.; Best, J. L. (Taylor & Francis, 2018-06-04)
    This paper describes a collaboration between a visual artist and geoscientists, who together viewed the same rugged, high mountain landscape through different, yet complementary, lenses. We pair scientific mapping and historic comparative photography with a series of site-specific sculptural installations to interpret the dramatic geological changes that occurred at Kaskawulsh Glacier, Yukon, in the spring of 2016. In the summer of that year, artist K.A. Colorado accompanied geoscientists D.H. Shugar, J.J. Clague, and J.L. Best to the terminus of Kaskawulsh Glacier, as well as Kluane Lake downstream of the glacier, to document the landscape changes that occurred earlier in the year. The Boundary images were created as on-site, three-dimensional, artistic interpretations of the markedly changed boundaries that occurred as a result of climate-induced glacier retreat and the sudden subcontinental-scale reorganization of drainage. Both the scientific study conducted by the geomorphologists and the art installations created by the artist were performed simultaneously. The Boundary installation art project, together with satellite imagery and historical photographs, conveys the death of Slims River as a result of climate change.
  • Ordovician origin and subsequent diversification of the brown algae
    Choi, Seok-Wan; Graf, Louis; Choi, Ji Won; Jo, Jihoon; Boo, Ga Hun; Kawai, Hiroshi; Choi, Chang Geun; Xiao, Shuhai; Knoll, Andrew H.; Andersen, Robert A.; Yoon, Hwan Su (Elsevier, 2024-01-19)
    Brown algae are the only group of heterokont protists exhibiting complex multicellularity. Since their origin, brown algae have adapted to various marine habitats, evolving diverse thallus morphologies and gamete types. However, the evolutionary processes behind these transitions remain unclear due to a lack of a robust phylogenetic framework and problems with time estimation. To address these issues, we employed plastid genome data from 138 species, including heterokont algae, red algae, and other red-derived algae. Based on a robust phylogeny and new interpretations of algal fossils, we estimated the geological times for brown algal origin and diversification. The results reveal that brown algae first evolved true multicellularity, with plasmodesmata and reproductive cell differentiation, during the late Ordovician Period (ca. 450 Ma), coinciding with a major diversification of marine fauna (the Great Ordovician Biodiversification Event) and a proliferation of multicellular green algae. Despite its early Paleozoic origin, the diversification of major orders within this brown algal clade accelerated only during the Mesozoic Era, coincident with both Pangea rifting and the diversification of other heterokont algae (e.g., diatoms), coccolithophores, and dinoflagellates, with their red algal-derived plastids. The transition from ancestral isogamy to oogamy was followed by three simultaneous reappearances of isogamy during the Cretaceous Period. These are concordant with a positive character correlation between parthenogenesis and isogamy. Our new brown algal timeline, combined with a knowledge of past environmental conditions, shed new light on brown algal diversification and the intertwined evolution of multicellularity and sexual reproduction.
  • Phylotranscriptomic insights into a Mesoproterozoic-Neoproterozoic origin and early radiation of green seaweeds (Ulvophyceae)
    Hou, Zheng; Ma, Xiaoya; Shi, Xuan; Li, Xi; Yang, Lingxiao; Xiao, Shuhai; De Clerck, Olivier; Leliaert, Frederik; Zhong, Bojian (Nature Portfolio, 2022-03-22)
    The Ulvophyceae, a major group of green algae, is of particular evolutionary interest because of its remarkable morphological and ecological diversity. Its phylogenetic relationships and diversification timeline, however, are still not fully resolved. In this study, using an extensive nuclear gene dataset, we apply coalescent- and concatenation-based approaches to reconstruct the phylogeny of the Ulvophyceae and to explore the sources of conflict in previous phylogenomic studies. The Ulvophyceae is recovered as a paraphyletic group, with the Bryopsidales being a sister group to the Chlorophyceae, and the remaining taxa forming a clade (Ulvophyceae sensu stricto). Molecular clock analyses with different calibration strategies emphasize the large impact of fossil calibrations, and indicate a Meso-Neoproterozoic origin of the Ulvophyceae (sensu stricto), earlier than previous estimates. The results imply that ulvophyceans may have had a profound influence on oceanic redox structures and global biogeochemical cycles at the Mesoproterozoic-Neoproterozoic transition.
  • Monte Carlo Simulation of Barrier-Island Systems and Tsunami Hazards
    Irish, Jennifer L.; Weiss, Robert; Dura, Tina (Coastal Engineering Research Council, 2023-09-01)
    Robust characterization of the future tsunami hazard is critically important for resilient planning and engineering in coastal communities prone to tsunami inundation. The hazard from earthquake-generated tsunami waves is not only determined by the earthquake's characteristics and distance to the earthquake area, but also by the geomorphology of the nearshore and onshore areas, which can change over time. In coastal hazard assessments, a changing coastal environment is commonly taken into account by increasing the sea-level to projected values (static). However, sea-level changes and other climate-change impacts influence the entire coastal system causing morphological change (dynamic). Here, we present the modeling framework and results initially published in Weiss et al. (2022), which employs within a Monte Carlo framework the barrier island-marsh, lagoon- marsh evolution model of Lorenzo-Trueba and Mariotti (2017) and the tsunami model Geoclaw (e.g., LeVeque et al. 2011). We compare the runup of the same suite of earthquake-generated tsunamis to a barrier system for statically adjusted and dynamically adjusted sea level and bathymetry over the period from 2000 to 2100. We employ Representative Concentration Pathways 2.6 and 8.5 without and with treatment of Antarctic ice-sheet processes (e.g., Kopp et al. 2017) as different sea-level projections.
  • Real-Time Prediction of Alongshore Near-Field Tsunami Runup Distribution From Heterogeneous Earthquake Slip Distribution
    Lee, Jun-Whan; Irish, Jennifer L.; Weiss, Robert (American Geophysical Union, 2023-01-05)
    Real-time tsunami prediction is necessary for tsunami forecasting. Although tsunami forecasting based on a precomputed tsunami simulation database is fast, it is difficult to respond to earthquakes that are not in the database. As the computation speed increases, various alternatives based on physics-based models have been proposed. However, physics-based models still require several minutes to simulate tsunamis and can have numerical stability issues that potentially make them unreliable for use in forecasting—particularly in the case of near-field tsunamis. This paper presents a data-driven model called the tsunami runup response function for finite faults (TRRF-FF) model that can predict alongshore near-field tsunami runup distribution from heterogeneous earthquake slip distribution in less than a second. Once the TRRF-FF model is trained and calibrated based on a discrete set of tsunami simulations, the TRRF-FF model can predict alongshore tsunami runup distribution from any combination of finite fault parameters. The TRRF-FF model treats the leading-order contribution and the residual part of the alongshore tsunami runup distribution separately. The interaction between finite faults is modeled based on the leading-order alongshore tsunami runup distribution. We validated the TRRF-FF modeling approach with more than 200 synthetic tsunami scenarios in eastern Japan. We further explored the performance of the TRRF-FF model by applying it to the 2011 Tohoku (Japan) tsunami event. The results show that the TRRF-FF model is more flexible, occupies much less storage space than a precomputed tsunami simulation database, and is more rapid and reliable than real-time physics-based numerical simulation.
  • Seismic Sources in the Aleutian Cradle of Tsunamis
    Witter, Rob; Briggs, Rich; Dura, Tina; Engelhart, Simon; Nelson, Alan (2022-10-01)
  • The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysis
    Reid, Rachel E. B.; Crowley, Brooke Erin; Haupt, Ryan J. (Wiley, 2023-12)
    What can the stable isotope values of human and animal faeces tell us? This often under-appreciated waste product is gaining recognition across a variety of disciplines. Faecal isotopes provide a means of monitoring diet, resource partitioning, landscape use, tracking nutrient inputs and cycling, and reconstructing past climate and environment. Here, we review what faeces are composed of, their temporal resolution, and how these factors may be impacted by digestive physiology and efficiency. As faeces are often used to explore diet, we clarify how isotopic offsets between diet and faeces can be calculated, as well as some differences among commonly used calculations that can lead to confusion. Generally, faecal carbon isotope (δ13C) values are lower than those of the diet, while faecal nitrogen isotope values (δ15N) values are higher than in the diet. However, there is considerable variability both within and among species. We explore the role of study design and how limitations stemming from a variety of factors can affect both the reliability and interpretability of faecal isotope data sets. Finally, we summarise the various ways in which faecal isotopes have been applied to date and provide some suggestions for future research. Despite remaining challenges, faecal isotope data are poised to continue to contribute meaningfully to a variety of fields.
  • The osteology of Shuvosaurus inexpectatus, a shuvosaurid pseudosuchian from the Upper Triassic Post Quarry, Dockum Group of Texas, USA
    Nesbitt, Sterling J.; Chatterjee, Sankar (Wiley, 2024-01-23)
    A vast array of pseudosuchian body plans evolved during the diversification of the group in the Triassic Period, but few can compare to the toothless, long-necked, and bipedal shuvosaurids. Members of this clade possess theropod-like character states mapped on top of more plesiomorphic pseudosuchian character states, complicating our understanding of the evolutionary history of the skeleton. One taxon in this clade, Shuvosaurus inexpectatus has been assigned to various theropod dinosaur groups based on a partial skull and referred material and its postcranium was assigned to a different taxon in Pseudosuchia. After the discovery of a skeleton of a shuvosaurid with a Shuvosaurus-like skull and a pseudosuchian postcranial skeleton, it became clear Shuvosaurus inexpectatus was a pseudosuchian. Nevertheless, a number of questions have arisen about what skeletal elements belonged to Shuvosaurus inexpectatus, the identification of skull bones, and the resulting implication for pseudosuchian evolution. Here, we detail the anatomy of the skeleton Shuvosaurus inexpectatus through a critical lens, parse out the bones that belong to the taxon or those that clearly do not or may not belong to the taxon, rediagnose the taxon based on these revisions, and compare the taxon to other archosaurs. We find that Shuvosaurus inexpectatus possesses similar anatomy to other shuvosaurids but parts of the skeleton of the taxon clarifies the anatomy of the group given that they are preserved in Shuvosaurus inexpectatus but not in others. Shuvosaurus inexpectatus is represented by at least 14 individuals from the West Texas Post Quarry (Adamanian holochronozone) and all Shuvosaurus inexpectatus skeletal material from the locality pertains to skeletally immature individuals. All of the skeletons are missing most of the neural arches, ribs, and most of the forelimb. We only recognize Shuvosaurus inexpectatus from the Post Quarry and all other material assigned to the taxon previously is better assigned to the broader group Shuvosauridae.
  • Geometrically frustrated interactions drive structural complexity in amorphous calcium carbonate
    Nicholas, Thomas C.; Stones, Adam Edward; Patel, Adam; Michel, F. Marc; Reeder, Richard J.; Aarts, Dirk G. A. L.; Deringer, Volker L.; Goodwin, Andrew L. (Nature Portfolio, 2023-09-25)
    Amorphous calcium carbonate is an important precursor for biomineralization in marine organisms. Key outstanding problems include understanding the structure of amorphous calcium carbonate and rationalizing its metastability as an amorphous phase. Here we report high-quality atomistic models of amorphous calcium carbonate generated using state-of-the-art interatomic potentials to help guide fits to X-ray total scattering data. Exploiting a recently developed inversion approach, we extract from these models the effective Ca⋯Ca interaction potential governing the structure. This potential contains minima at two competing distances, corresponding to the two different ways that carbonate ions bridge Ca2+-ion pairs. We reveal an unexpected mapping to the Lennard-Jones–Gauss model normally studied in the context of computational soft matter. The empirical model parameters for amorphous calcium carbonate take values known to promote structural complexity. We thus show that both the complex structure and its resilience to crystallization are actually encoded in the geometrically frustrated effective interactions between Ca2+ ions. [Figure not available: see fulltext.]
  • Room-Temperature Intrinsic and Extrinsic Damping in Polycrystalline Fe Thin Films
    Wu, Shuang; Smith, David A.; Nakarmi, Prabandha; Rai, Anish; Clavel, Michael; Hudait, Mantu K.; Zhao, Jing; Michel, F. Marc; Mewes, Claudia; Mewes, Tim; Emori, Satoru (2021-09-08)
    We examine room-temperature magnetic relaxation in polycrystalline Fe films. Out-of-plane ferromagnetic resonance (FMR) measurements reveal Gilbert damping parameters of $\approx$ 0.0024 for Fe films with thicknesses of 4-25 nm, regardless of their microstructural properties. The remarkable invariance with film microstructure strongly suggests that intrinsic Gilbert damping in polycrystalline metals at room temperature is a local property of nanoscale crystal grains, with limited impact from grain boundaries and film roughness. By contrast, the in-plane FMR linewidths of the Fe films exhibit distinct nonlinear frequency dependences, indicating the presence of strong extrinsic damping. To fit our in-plane FMR data, we have used a grain-to-grain two-magnon scattering model with two types of correlation functions aimed at describing the spatial distribution of inhomogeneities in the film. However, neither of the two correlation functions is able to reproduce the experimental data quantitatively with physically reasonable parameters. Our findings advance the fundamental understanding of intrinsic Gilbert damping in structurally disordered films, while demonstrating the need for a deeper examination of how microstructural disorder governs extrinsic damping.
  • Operando characterization and regulation of metal dissolution and redeposition dynamics near battery electrode surface
    Zhang, Yuxin; Hu, Anyang; Xia, Dawei; Hwang, Sooyeon; Sainio, Sami; Nordlund, Dennis; Michel, F. Marc; Moore, Robert B.; Li, Luxi; Lin, Feng (Nature Portfolio, 2023-07)
    Mn dissolution has been a long-standing, ubiquitous issue that negatively impacts the performance of Mn-based battery materials. Mn dissolution involves complex chemical and structural transformations at the electrode–electrolyte interface. The continuously evolving electrode–electrolyte interface has posed great challenges for characterizing the dynamic interfacial process and quantitatively establishing the correlation with battery performance. In this study, we visualize and quantify the temporally and spatially resolved Mn dissolution/redeposition (D/R) dynamics of electrochemically operating Mn-containing cathodes. The particle-level and electrode-level analyses reveal that the D/R dynamics is associated with distinct interfacial degradation mechanisms at different states of charge. Our results statistically differentiate the contributions of surface reconstruction and Jahn–Teller distortion to the Mn dissolution at different operating voltages. Introducing sulfonated polymers (Nafion) into composite electrodes can modulate the D/R dynamics by trapping the dissolved Mn species and rapidly establishing local Mn D/R equilibrium. This work represents an inaugural effort to pinpoint the chemical and structural transformations responsible for Mn dissolution via an operando synchrotron study and develops an effective method to regulate Mn interfacial dynamics for improving battery performance.
  • Effects of Oxyanion Surface Loading on the Rate and Pathway of Ferrihydrite Transformation
    Namayandeh, Alireza; Borkiewicz, Olaf J.; Bompoti, Nefeli M.; Watson, Steven K.; Kubicki, James D.; Chrysochoou, Maria; Michel, F. Marc (American Chemical Society, 2023-10-19)
    In natural environments, ferrihydrite (Fh) reacts readily with the contaminant and nutrient oxyanions through surface complexation. While previous experiments showed that the transformation of Fh to Gt and Hm under oxic conditions at 70 °C is controlled by the type and strength of oxyanion surface complexes, the impact of surface loading on this process is only partly understood. Synchrotron scattering methods and chemical analysis were used to develop a kinetic model that describes the impact of oxyanion surface loading on the rate and pathway of Fh transformation by using arsenate (AsO43-) and phosphate (PO43-). Kinetic modeling showed that AsO43- and PO43- adsorption decreased the rate of transformation and favored Hm formation over Gt. Higher surface loadings increasingly inhibited Fh transformation with a greater effect for PO43- compared with AsO43-. This information has implications for understanding the impacts of oxyanions on the transformation of natural Fe to Gt and Hm in environmental systems.
  • Thermal Conductivity of the Martian Soil at the InSight Landing Site From HP3 Active Heating Experiments
    Grott, M.; Spohn, T.; Knollenberg, J.; Krause, C.; Hudson, T. L.; Piqueux, S.; Mueller, N.; Golombek, M.; Vrettos, C.; Marteau, E.; Nagihara, S.; Morgan, P.; Murphy, J. P.; Siegler, M.; King, Scott D.; Smrekar, S. E.; Banerdt, W. B. (American Geophysical Union, 2021-07-14)
    The heat flow and physical properties package (HP3) of the InSight Mars mission is an instrument package designed to determine the martian planetary heat flow. To this end, the package was designed to emplace sensors into the martian subsurface and measure the thermal conductivity as well as the geothermal gradient in the 0–5 m depth range. After emplacing the probe to a tip depth of 0.37 m, a first reliable measurement of the average soil thermal conductivity in the 0.03–0.37 m depth range was performed. Using the HP3 mole as a modified line heat source, we determined a soil thermal conductivity of 0.039 ± 0.002 W m−1 K−1, consistent with the results of orbital and in-situ thermal inertia estimates. This low thermal conductivity implies that 85%–95% of all particles are smaller than 104–173 μm and suggests that soil cementation is minimal, contrary to the considerable degree of cementation suggested by image data. Rather, cementing agents like salts could be distributed in the form of grain coatings instead. Soil densities compatible with the measurements are (Formula presented.) kg m−3, indicating soil porosities of (Formula presented.) %.
  • Volcanic Activity on Venus: How Long Must We Look to Find a Smoking Gun?
    King, Scott D. (American Geophysical Union, 2022-04-04)
    While volcanic landforms attest to the numerous and varied volcanic processes on Venus, estimates of the frequency of volcanic eruptions are lacking. Constraints from volcanic resurfacing volumes can be equally satisfied by infrequent large eruptions or numerous smaller events. Recently, Byrne and Krishnamoorthy (2022),, used the 40-year period from 1980 to 2020 from the Smithsonian Global Volcanism Program (GVP) database (Global Volcanism Program, 2013) to extrapolate the frequency of volcanic events on Earth to Venus. They evaluated the tectonic settings from the GVP database and provided estimates that consider the differences in those settings between Earth and Venus. Byrne and Krishnamoorthy extrapolated the rate of volcanism between Earth and Venus using the mass/volume ratios, freeing their results from the uncertain tectonic evolution of Venus. The assumption that Venus is in a stagnant-lid tectonic regime with a straight-forward geodynamic evolution has been challenged by Weller and Kiefer (2020),, who showed that a planetary surface may reflect different styles of convection with highly active and sluggish and inactive regions occurring at the same time. The straight-forward scaling allowed Byrne and Krishnamoorthy to estimate that as many as 120 eruptions might take place on Venus every year, a frequency that should be detectable by upcoming Venus missions.
  • Machine learning and marsquakes: a tool to predict atmospheric-seismic noise for the NASA InSight mission
    Stott, A. E.; Garcia, R. F.; Chedozeau, A.; Spiga, A.; Murdoch, N.; Pinot, B.; Mimoun, D.; Charalambous, C.; Horleston, A.; King, Scott D.; Kawamura, T.; Dahmen, N.; Barkaoui, S.; Lognonne, P.; Banerdt, W. B. (Oxford University Press, 2023-01-04)
    The SEIS (seismic experiment for the interior structure of Mars) experiment on the NASA InSight mission has catalogued hundreds of marsquakes so far. However, the detectability of these events is controlled by the weather which generates noise on the seismometer. This affects the catalogue on both diurnal and seasonal scales. We propose to use machine learning methods to fit the wind, pressure and temperature data to the seismic energy recorded in the 0.4–1 and 2.2–2.6 Hz bandwidths to examine low- (LF) and high-frequency (HF) seismic event categories respectively. We implement Gaussian process regression and neural network models for this task. This approach provides the relationship between the atmospheric state and seismic energy. The obtained seismic energy estimate is used to calculate signal-to-noise ratios (SNR) of marsquakes for multiple bandwidths. We can then demonstrate the presence of LF energy above the noise level during several events predominantly categorized as HF, suggesting a continuum in event spectra distribution across the marsquake types. We introduce an algorithm to detect marsquakes based on the subtraction of the predicted noise from the observed data. This algorithm finds 39 previously undetected marsquakes, with another 40 possible candidates. Furthermore, an analysis of the detection algorithm’s variable threshold provides an empirical estimate of marsquake detectivity. This suggests that events producing the largest signal on the seismometer would be seen almost all the time, the median size signal event 45–50 per cent of the time and smallest signal events 5−20 per cent of the time.
  • Surface waves and crustal structure on Mars
    Kim, D.; Banerdt, W. B.; Ceylan, S.; Giardini, D.; Lekic, V.; Lognonne, P.; Beghein, C.; Beucler, E.; Carrasco, S.; Charalambous, C.; Clinton, J.; Drilleau, M.; Duran, C.; Golombek, M.; Joshi, R.; Khan, A.; Knapmeyer-Endrun, B.; Li, J.; Maguire, R.; Pike, W. T.; Samuel, H.; Schimmel, M.; Schmerr, N. C.; Stahler, S. C.; Stutzmann, E.; Wieczorek, M.; Xu, Z.; Batov, A.; Bozdag, E.; Dahmen, N.; Davis, P.; Gudkova, T.; Horleston, A.; Huang, Q.; Kawamura, T.; King, Scott D.; McLennan, S. M.; Nimmo, F.; Plasman, M.; Plesa, A. C.; Stepanova, I. E.; Weidner, E.; Zenhausern, G.; Daubar, I. J.; Fernando, B.; Garcia, R. F.; Posiolova, L.; Panning, M. P. (AAAS, 2022-10-28)
    We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.
  • Elucidating the magma plumbing system of Ol Doinyo Lengai (Natron Rift, Tanzania) Using satellite geodesy and numerical modeling
    Daud, Ntambila; Stamps, D. Sarah; Battaglia, Maurizio; Huang, Mong-Han; Saria, Elifuraha; Ji, Kang-Hyeun (Elsevier, 2023-06)
    Ol Doinyo Lengai, located in the southern Eastern Branch of the East African Rift had several eruptive episodes with ash falls and lava flows (VEI 3) that caused damage to the nearby communities between 2007 and 2010. The volcano is remote and access is difficult. Although this volcano has been studied for decades, its plumbing system is still poorly understood, in part, because of the lack of precise observations of surface deformation during periods of quiet and unrest. This study investigates the volcanic plumbing system of Ol Doinyo Lengai and its surroundings using data from the network of permanent Global Navigation Satellite System (GNSS) sites monitoring the volcano (the TZVOLCANO network) around the flanks of the volcano and Interferometric Synthetic Aperture Radar (InSAR) observations. We constrain surface motions using 6 GNSS sites distributed around Ol Doinyo Lengai, operating between 2016 and 2021, and InSAR data covering nearly the same time period. Because of the complex local tectonics, the interpretation of the deformation pattern is not straightforward. We first invert the GNSS deformation and InSAR observations independently to infer potential deformation sources. Then we perform a joint inversion of both GNSS and InSAR datasets to verify our findings. We compare the results from the joint inversion with the results from inverting each dataset independently. The GNSS, InSAR, and joint inversion results point to a deflating source, located east of Ol Doinyo Lengai and southwest of the dormant volcano Gelai at a depth of 3.49 ± 0.03 km (GNSS inversion), 5.2 ± 1.2 km (InSAR inversion) and 3.49 ± 0.06 km (joint inversion) relative to the summit (vent) and with a volume change ∆V of −0.04 ± 0.05 × 106 m3 (GNSS inversion), −0.39 ± 0.29 × 106 m3 (InSAR inversion), and − 0.04 ± 0.01 × 106 m3 (joint inversion). Although this is non-unique modeling of geodetic datasets with small signals, the inversion results suggest that Ol Doinyo Lengai could be fed by an offset multi-reservoir system that includes a shallow magma reservoir (<5 km) east of Ol Doinyo Lengai, possibly connected to a deeper magma reservoir.
  • Slowly but surely: Exposure of communities and infrastructure to subsidence on the US east coast
    Ohenhen, Leonard; Shirzaei, Manoochehr; Barnard, Patrick L. (Oxford University Press, 2024-01-02)
    Coastal communities are vulnerable to multihazards, which are exacerbated by land subsidence. On the US east coast, the high density of population and assets amplifies the region's exposure to coastal hazards. We utilized measurements of vertical land motion rates obtained from analysis of radar datasets to evaluate the subsidence-hazard exposure to population, assets, and infrastructure systems/facilities along the US east coast. Here, we show that 2,000 to 74,000 km² land area, 1.2 to 14 million people, 476,000 to 6.3 million properties, and >50% of infrastructures in major cities such as New York, Baltimore, and Norfolk are exposed to subsidence rates between 1 and 2 mm per year. Additionally, our analysis indicates a notable trend: as subsidence rates increase, the extent of area exposed to these hazards correspondingly decreases. Our analysis has far-reaching implications for community and infrastructure resilience planning, emphasizing the need for a targeted approach in transitioning from reactive to proactive hazard mitigation strategies in the era of climate change.
  • Development of a lateral topographic weathering gradient in temperate forested podzols
    Bower, Jennifer A.; Ross, Donald S.; Bailey, Scott W.; Pennino, Amanda M.; Jercinovic, Michael J.; McGuire, Kevin J.; Strahm, Brian D.; Schreiber, Madeline E. (Elsevier, 2023-11)
    Mineral weathering is an important soil-forming process driven by the interplay of water, organisms, solution chemistry, and mineralogy. The influence of hillslope-scale patterns of water flux on mineral weathering in soils is still not well understood, particularly in humid postglacial soils, which commonly harbor abundant weatherable primary minerals. Previous work in these settings showed the importance of lateral hydrologic patterns to hillslope-scale pedogenesis. In this study, we hypothesized that there is a corresponding relationship between hydrologically driven pedogenesis and chemical weathering in podzols in the White Mountains of New Hampshire, USA. We tested this hypothesis by quantifying the depletion of plagioclase in the fine fraction (≤2 mm) of closely spaced, similar-age podzols along a gradient in topography and depth to bedrock that controls lateral water flow. Along this gradient, laterally developed podzols formed through frequent, episodic flushing by upslope groundwater, and vertically developed podzols formed through characteristic vertical infiltration. We estimated the depletion of plagioclase-bound elements within the upper mineral horizons of podzols using mass transfer coefficients (τ) and quantified plagioclase losses directly through electron microscopy and microprobe analysis. Elemental depletion was significantly more pronounced in the upslope lateral eluvial (E horizon-dominant) podzols relative to lateral illuvial (B horizon-dominant) and vertical (containing both E and B horizons) podzols downslope, with median Na losses of ∼74 %, ∼56 %, and ∼40 %, respectively. When comparing genetic E horizons, Na and Al were significantly more depleted in laterally developed podzols relative to vertically developed podzols. Microprobe analysis revealed that ∼74 % of the plagioclase was weathered from the mineral pool of lateral eluvial podzols, compared to ∼39 % and ∼23 % for lateral illuvial podzols and vertically developed podzols, respectively. Despite this intense weathering, plagioclase remains the second most abundant mineral in soil thin sections. These findings confirm that the concept of soil development as occurring vertically does not accurately characterize soils in topographically complex regions. Our work improves the current understanding of pedogenesis by identifying distinct, short-scale gradients in mineral weathering shaped by local patterns of hydrology and topography.