Scholarly Works, Geosciences

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Micro-CT data reveal new information on the craniomandibular and neuroanatomy of the dicynodont Gordonia (Therapsida: Anomodontia) from the late Permian of Scotland
George, Hady; Kammerer, Christian F.; Foffa, Davide; Clark, Neil D. L.; Brusatte, Stephen L. (Oxford University Press, 2025-03-01)
Dicynodontia was an abundant, globally widespread clade of Permo-Triassic synapsids on the stem lineage of mammals. Although there is an extensive body of literature on dicynodont craniomandibular anatomy, only recently has the power of computed tomographic (CT) scanning been applied to this system. CT-assisted research on dicynodonts has focused on the smallest members of the clade, while larger dicynodonts (particularly the members of the diverse, long-ranging subclade Bidentalia) have received comparatively little attention. Here, we work towards filling that gap by presenting a mu CT-assisted reconstruction of 'The Elgin Marvel', a bidentalian specimen consisting of a complete cranium and mandible from late Permian deposits near Elgin, Scotland, which historically has been difficult to study because of its unusual preservation as void space in sandstone. This specimen can be referred to Gordonia, which is solely represented by moulds of void specimens. The mu CT data reveal new information on the palate and endocranium of this taxon that could not previously be gleaned from physical moulds made from the void specimens. A phylogenetic analysis indicates that Gordonia and the Chinese Jimusaria form a clade of bidentalians characterized by narrow pterygoid medial plates, expanding our understanding of late Permian biogeography. The endocast of Gordonia is similar to that of other non-cynodont therapsids, and has a remarkably enlarged pineal body, probably related to exaggeration of the sagittal crest. Comparisons of encephalization quotients (EQ), a measure of brain size relative to body size, reveal Gordonia has a similar EQ to most other non-cynodont therapsids.
A novel hybrid GNSS, GRACE, and InSAR joint inversion approach to constrain water loss during a record-setting drought in California
Carlson, Grace; Werth, Susanna; Shirzaei, Manoochehr (Elsevier, 2024-09-01)
Water years 2020 and 2021 in California were two of the driest on record and the most recent series of dry years during a two-decade-long mega-drought. The 2020-2021 drought period, characterized by low precipitation and high temperatures, had devastating effects, including an increase in ongoing groundwater overdraft, manifesting in rapid subsidence in California's Central Valley. Here, we present a unified hybrid physics-based stochastic model incorporating measurements from three geodetic sensors to produce a high-resolution map of terrestrial water storage change (Delta TWS) across California during the 2020-2021 dry years. The novel joint inversion framework combines Global Navigation Satellite System (GNSS) elastic vertical displacements, Delta TWS from the Gravity Recovery and Climate Experiment Satellites (GRACE and the follow-on mission, GRACE-FO) and Interferometric Synthetic Aperture Radar (InSAR) measurements of poroelastic deformation through a model comprising elastic loading and poroelastic Green's functions. This framework yields a high-resolution and more realistic estimate of Delta TWS within the Central Valley and the surrounding mountain ranges by accounting for poroelastic aquifer deformation. Besides the total Delta TWS, our novel inversion framework simultaneously solves the change in groundwater storage and is used to produce a high-resolution map of groundwater storage loss across the Central Valley. We calculate a groundwater volume loss of 20.4+/- 2.6 km3 in the semi-confined to confined portion of the aquifer-system, with the largest groundwater volume loss in the southern Central Valley over the two dry years. We show that groundwater loss estimates found using our joint inversion framework agree with results from a conventional approach for GRACE-FO-derived groundwater loss estimates when considering underlying processes and uncertainties. Finally, we compare shallow groundwater storage change estimates with those derived from in-situ groundwater level measurements in the Sacramento Valley.
Sustained increases in atmospheric oxygen and marine productivity in the Neoproterozoic and Palaeozoic eras
Stockey, Richard G.; Cole, Devon B.; Farrell, Una C.; Agic, Heda; Boag, Thomas H.; Brocks, Jochen J.; Canfield, Don E.; Cheng, Meng; Crockford, Peter W.; Cui, Huan; Dahl, Tais W.; Del Mouro, Lucas; Dewing, Keith; Dornbos, Stephen Q.; Emmings, Joseph F.; Gaines, Robert R.; Gibson, Timothy M.; Gill, Benjamin C.; Gilleaudeau, Geoffrey J.; Goldberg, Karin; Guilbaud, Romain; Halverson, Galen; Hammarlund, Emma U.; Hantsoo, Kalev; Henderson, Miles A.; Henderson, Charles M.; Hodgskiss, Malcolm S. W.; Jarrett, Amber J. M.; Johnston, David T.; Kabanov, Pavel; Kimmig, Julien; Knoll, Andrew H.; Kunzmann, Marcus; LeRoy, Matthew A.; Li, Chao; Loydell, David K.; Macdonald, Francis A.; Magnall, Joseph M.; Mills, N. Tanner; Och, Lawrence M.; O'Connell, Brennan; Pages, Anais; Peters, Shanan E.; Porter, Susannah M.; Poulton, Simon W.; Ritzer, Samantha R.; Rooney, Alan D.; Schoepfer, Shane; Smith, Emily F.; Strauss, Justin V.; Uhlein, Gabriel Jube; White, Tristan; Wood, Rachel A.; Woltz, Christina R.; Yurchenko, Inessa; Planavsky, Noah J.; Sperling, Erik A. (Nature Portfolio, 2024-07-01)
A geologically rapid Neoproterozoic oxygenation event is commonly linked to the appearance of marine animal groups in the fossil record. However, there is still debate about what evidence from the sedimentary geochemical record-if any-provides strong support for a persistent shift in surface oxygen immediately preceding the rise of animals. We present statistical learning analyses of a large dataset of geochemical data and associated geological context from the Neoproterozoic and Palaeozoic sedimentary record and then use Earth system modelling to link trends in redox-sensitive trace metal and organic carbon concentrations to the oxygenation of Earth's oceans and atmosphere. We do not find evidence for the wholesale oxygenation of Earth's oceans in the late Neoproterozoic era. We do, however, reconstruct a moderate long-term increase in atmospheric oxygen and marine productivity. These changes to the Earth system would have increased dissolved oxygen and food supply in shallow-water habitats during the broad interval of geologic time in which the major animal groups first radiated. This approach provides some of the most direct evidence for potential physiological drivers of the Cambrian radiation, while highlighting the importance of later Palaeozoic oxygenation in the evolution of the modern Earth system.
Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water-Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts
Knight, Brenna M.; Mondal, Ronnie; Han, Nizhou; Pietra, Nicholas F.; Hall, Brady A.; Edgar, Kevin J.; Welborn, Valerie Vaissier; Madsen, Louis A.; De Yoreo, James J.; Dove, Patricia M. (American Chemical Society, 2024-07-11)
Anionic macromolecules are found at sites of CaCO3 biomineralization in diverse organisms, but their roles in crystallization are not well-understood. We prepared a series of sulfated chitosan derivatives with varied positions and degrees of sulfation, DS(SO3-), and measured calcite nucleation rate onto these materials. Fitting the classical nucleation theory model to the kinetic data reveals the interfacial free energy of the calcite-polysaccharide-solution system, gamma(net), is lowest for nonsulfated controls and increases with DS(SO3-). The kinetic prefactor also increases with DS(SO3-). Simulations of Ca2+-H2O-chitosan systems show greater water structuring around sulfate groups compared to uncharged substituents, independent of sulfate location. Ca2+-SO3- interactions are solvent-separated by distances that are inversely correlated with DS(SO3-) of the polysaccharide. The simulations also predict SO3- and NH3+ groups affect the solvation waters and HCO3- ions associated with Ca2+. Integrating the experimental and computational evidence suggests sulfate groups influence nucleation by increasing the difficulty of displacing near-surface water, thereby increasing gamma(net). By correlating gamma(net) and net charge per monosaccharide for diverse polysaccharides, we suggest the solvent-separated interactions of functional groups with Ca2+ influence thermodynamic and kinetic components to crystallization by similar solvent-dominated processes. The findings reiterate the importance of establishing water structure and properties at macromolecule-solution interfaces.
Induced seismicity and surface deformation associated with long-term and abrupt geothermal operations in Blue Mountain, Nevada
Koirala, Roshan; Kwiatek, Grzegorz; Shirzaei, Manoochehr; Brodsky, Emily; Cladouhos, Trenton; Swyer, Michael; Goebel, Thomas (Elsevier, 2024-10-01)
Geothermal reservoir operations can lead to seismic activity, for instance, due to increased pore pressure, but some observations are difficult to explain by pressure changes alone. Such observations include unexpected, induced events after injection well shut-in when pore pressures are thought to decrease. Here, we analyze induced seismicity up to ML 1.5 and surface deformation in Blue Mountain, Nevada using seismic, geodetic, and hydraulic data between 2016 and 2020. This period is characterized by long-term surface subsidence of up to 1 cm/yr above the reservoir. The long-term deformation is associated with modest seismic activity but also shortlived seismicity spikes during rapid maintenance shutdowns in 2017 and 2018. The seismicity is concentrated within the geothermal reservoir at 0.5 - 2.5 km depth, similar to injection operations. We present a numerical model of abrupt seismicity rate changes during the two shutdowns that explains the observation through short-term poroelastic effects leading to increased Coulomb stressing rates. In contrast, the long-term surface subsidence can be modeled statically by superimposing localized fault slip, and thermal contraction of the reservoir. Our findings demonstrate that poroelastic coupling drives the abrupt increase in seismic activity following well shutdown, while aseismic fault slip and thermal contraction dictate the long-term static deformation.
Ore mineralization in the Mofete and San Vito geothermal fields, Campi Flegrei volcanic complex, Naples, Italy
Belkin, Harvey E.; McAleer, Ryan J.; De Vivo, Benedetto (Elsevier, 2024-10-01)
The Mofete and San Vito geothermal fields, located west of Naples, Italy, are part of the Campi Flegrei volcanic complex. In the 1970s, exploratory wells were drilled to a depth of similar to 3000 m in an attempt to locate highenthalpy fluids for potential power production. Drill core samples from Mofete wells (MF1, MF2, and MF5) and from San Vito wells (SV1 and SV3) contain authigenic ore mineralization. Pyrite, pyrrhotite, and galena are abundant. Less common are chalcopyrite, sphalerite, arsenopyrite, and scheelite; rare are millerite, violarite, native bismuth, tellurobismuthite, cassiterite, molybdenite, and acanthite. Mineral chemistry was determined by electron microprobe wavelength dispersive spectroscopy aided by a scanning electron microscope equipped with energy-dispersive spectroscopy. The mineral assemblage suggests a low sulfidation environment and the absence of pyrrhotite in the MF1 well and upper part of the SV1 well indicates variable sulfur activity. Both molybdenite and scheelite were identified in samples SV1-2860 and SV3-2353 and scheelite in the SV3 well is zoned with variable Mo6+ content; low Mo6+ zones show blue cathodoluminescence, whereas, zones with high Mo6+ content are yellow to brown. Zoned scheelite and the occurrence of both Mo-bearing minerals attest to the variability of fO(2) and fS(2) in the geothermal fluid.
Building damage risk in sinking Indian megacities
Sadhasivam, Nitheshnirmal; Ohenhen, Leonard O.; Khorrami, Mohammad; Werth, Susanna; Shirzaei, Manoochehr (Nature Portfolio, 2025-10-28)
Building damage poses serious safety risks, causing substantial financial losses worldwide. Engineering shortcomings are commonly cited as the cause of long-term structural failures, often neglecting the exacerbating role of land subsidence. Here we used satellite radar observations during 2015–2023 to estimate differential settlements at 5 fast-growing Indian megacities, including more than 13 million buildings and 80 million people. Our analysis reveals 878 km² of land subsiding, exposing ~1.9 million people to subsidence rates of more than 4 mm yr−1. An estimated 2,406 buildings across Delhi, Mumbai and Chennai are at high risk of structural damage from ongoing land subsidence. Sustained over 50 years, current subsidence rates could place as many as 23,529 buildings at very high risk of structural damage in Chennai, Delhi, Mumbai, Kolkata and Bengaluru. Our results highlight the compounding risk of infrastructure damage from subsidence, assisting policymakers to develop resilience plans and adaptation strategies that prioritize mitigation and maintenance spending.
On the role of inherited rock fabric in critical zone porosity development: Insights from seismic anisotropy measurements using surface waves
Eppinger, Benjamin J.; Holbrook, W. Steven; Flinchum, Brady A.; Grana, Dario; Richter, Daniel de B.; Hayes, Jorden L.; Riebe, Clifford S.; Harman, Ciaran J.; Carr, Bradley J. (Wiley, 2025-07)
Within Earth's critical zone, weathering processes influence landscape evolution and hillslope hydrology by creating porosity in bedrock, transforming it into saprolite and eventually soil. In situ weathering processes drive much of this transformation while preserving the rock fabric of the parent material. Inherited rock fabric in regolith makes the critical zone anisotropic, affecting its mechanical and hydrological properties. Therefore, quantifying and studying anisotropy is an important part of characterising the critical zone, yet doing so remains challenging. Seismic methods can be used to detect rock fabric and infer mechanical and hydrologic conductivity anisotropy across landscapes. We present a novel way of measuring seismic anisotropy in the critical zone using Rayleigh and Love surface waves. This method leverages multi-component surface seismic data to create a high-resolution model of seismic anisotropy, which we compare with a nuclear magnetic resonance log measured in a nearby borehole. The two geophysical data sets show that seismic anisotropy and porosity develop at similar depths in weathered bedrock and both reach their maximum values in saprolite, implying that in situ weathering enhances anisotropy while concurrently generating porosity in the critical zone. We bolster our findings with in situ measurements of seismic and hydrologic conductivity anisotropy made in a 3 m deep soil excavation. Our study offers a fresh perspective on the importance of rock fabric in the development and function of the critical zone and sheds new insights into how weathering processes operate.
Seismicity zoning at Coso geothermal field and stress changes from fluid production and migration
Tung, Sui; Kaven, Ole; Shirzaei, Manoochehr; Masterlark, Timothy; Wang, Herbert F.; Huang, Wei-Chuang; Feigl, Kurt L. (Elsevier, 2024-11-15)
The Coso geothermal field is a major geothermal power production site in the western United States. It has been observed that low-magnitude seismic events (M < 3.71) are unevenly distributed in three distinct zones, namely, nearfield (<3 km), midfield (3-6 km), and farfield (> 6 km) from the Coso geothermal plant. These zones exhibit distinct changes in earthquake location before and during geothermal production episodes that began in 1986. After 1986, the midfield region of the main flank experiences a significantly lower seismicity rate than the surrounding areas before production episodes. During 2014-2019, the farfield earthquakes cluster in the eastern and western parts of the greater Coso area, which is discernably different from how those pre-production earthquake events were distributed along the conjugate NW-SE and SW-NW trending structures across the main flank. Here, we analyze the stage of stress with finite-element-based poroelastic simulations to illustrate how the spatiotemporal evolution of the seismicity is associated with the pattern of stress perturbations caused by fluid migration amid the operations of geothermal power plants. Generally, similar to 70% of co-production seismicity is found in zones of increased Coulomb stress between 2014 and 2019 at >99% confidence. Meanwhile, the midfield zone of seismic paucity overlaps with the zone of decreasing pore-fluid pressure. Overall, the results provide a physical explanation of how decadal geothermal operations at Coso have perturbed stress-field changes and contributed to the evolving characteristic seismic pattern, shedding insights into assessing the seismic hazard in other geothermal settings.
A Cnidarian affinity for Salterella and Volborthella: implications for the evolution of shells
Vayda, Prescott J.; Xiao, Shuhai; Keller, Noah D.; Hagen, Amy P. I.; Strauss, Justin V.; Hagadorn, James W.; Lonsdale, Mary C.; Selly, Tara; Schiffbauer, James D. (Cambridge University Press, 2025-10-13)
The Cambrian Explosion saw the widespread development of mineralized skeletons. At this time, nearly every major animal phylum independently evolved strategies to build skeletons through either agglutination or biomineralization. Although most organisms settled on a single strategy, Salterella Billings, 1865 employed both strategies by secreting a biocalcitic exterior shell that is lined with layers of agglutinated sediments surrounding a central hollow tube. The slightly older fossil, Volborthella Schmidt, 1888, shares a similar construction with agglutinated grains encompassing a central tube but lacks a biomineralized exterior shell. Together these fossils have been grouped in the phylum Agmata Yochelson, 1977, although no phylogenetic relationship has been suggested to link them with the broader metazoan tree, which limits their contribution to our understanding of the evolution of shells in early animals. To understand their ecology and place them in a phylogenetic context, we investigated Salterella and Volborthella fossils from the Wood Canyon and Harkless formations of Nevada, USA, the Illtyd Formation of Yukon, Canada, and the Shady Formation of Virginia, USA.Thin-section petrography, acid maceration, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray tomographic microscopy were used to provide new insights into these enigmatic faunas. First, morphological similarities in the aperture divergence angle and ratio of central tube diameter to agglutinated layer thickness suggest Salterella and Volborthella are related. Second, both fossils exhibit agglutinated grain compositions that are distinctive from their surrounding environments and demonstrate selectivity on the part of their producers. Finally, the calcitic shell composition and simple layers of blocky prismatic shell microstructure in Salterella suggest a possible cnidarian affinity. Together these data point to these organisms being sessile, semi-infaunal filter or deposit feeders and an early experimentation in cnidarian biomineralization chronicling a hypothesized transition from an organic sheath in Volborthella to a biomineralized shell in Salterella.
Tapping into the success of Science on Tap New River Valley: Lessons learned from eight years of a community-centered science outreach program
Hagen, Amy P. I.; DeNunzio, Maria; Kroehler, Carolyn J.; Chen, S.; Goh, Ying-Xian; Burke, K. L.; Oyedele, E.; Hockman, C.; Vayda, P.; Bracci, Nicole R.; Pagani, M.; Good, Deborah J.; Pfeiffer, Douglas G.; Allen, E.; Raun, Patricia (2025-10)
Communicating scientific research to the public through outreach programs is beneficial but faces many challenges. These include impediments to designing and implementing sustainable outreach programming as well as communication challenges between scientists and audience. Here we present Science on Tap New River Valley (NRV), a community-centered monthly science outreach program designed to reduce barriers to effective science outreach and share research with residents of the New River Valley in Virginia. The program places special emphasis on interactivity with community members and provides support for speakers to ensure that this goal is met. With a relatively small budget and a primarily graduate student-led volunteer organizing team, Science on Tap NRV serves as a model of a sustainable outreach program that provides opportunities for community members to engage with scientists, researchers to build and practice their science communication skills, and graduate students to learn to coordinate and implement effective outreach events. We share the details of the factors that have contributed to the success of Science on Tap NRV since 2017.
Precambrian Earth: Co-evolution of life and geodynamics
Westall, Frances; Xiao, Shuhai (Elsevier, 2024-11-01)
The Precambrian covers 80% of the history the Earth. In this timespan, the Earth developed from an anaerobic planet to the oxygenic planet dominated by Wilson-style plate tectonics that we know today. Concomitant with geological evolution, life emerged and evolved, gradually colonising all known aqueous habitats. Until the Palaeoarchaean, life was largely dominated by its geological environment. However, as of the Mesoarchaean, when there were major changes in geodynamics leading to continental erosion and runoff of essential nutrients, the effects of life started to impinge on the geological environment. The interaction of life and Earth was and is reciprocal, hence the term biogeodynamics. In this review, we trace the evolution of geology and life in parallel, thus highlighting the gradual buildup of the importance of life on terrestrial processes, and the importance of changes in the geological environment on the evolution of life. We do not attempt to make an exhaustive review of all the occurrences of life in the Precambrian but use selected examples to illustrate key events and changes. We conclude by addressing certain aspects of the evolution of life that require more in-depth study and show how the finding of extra-terrestrial life would advance our understanding of life on Earth.
Osteohistological signal from the smallest known phytosaur femur reveals slow growth and new insights into the evolution of growth in Archosauria
Goldsmith, Erika R.; Barta, Daniel E.; Kligman, Ben T.; Nesbitt, Sterling J.; Marsh, Adam D.; Parker, William G.; Stocker, Michelle R. (Wiley, 2024-12-03)
Fossils of embryonic and hatchling individuals can provide invaluable insight into the evolution of prenatal morphologies, heterochronies, and allometric trajectories within Archosauria but are exceptionally rare in the Triassic fossil record, obscuring a critical aspect of archosaurian biology during their evolutionary origins. Microvertebrate sampling at a single bonebed in the Upper Triassic Chinle Formation within Petrified Forest National Park has yielded diminutive archosauriform femora (PEFO 45274, PEFO 45199) with estimated and measured femoral lengths of similar to 31 mm and similar to 37 mm, respectively. These new specimens provide the unique opportunity to assess the preservation, body size, and growth dynamics of skeletally immature archosauriforms in North America and compare the growth dynamics of archosauromorphs within an evolutionary and ontogenetic context. We assign PEFO 45199 and PEFO 45274 to Phytosauria (Archosauriformes) based on their strongly sigmoidal shape in lateral view, the presence of proximal anterolateral and posteromedial tubera, the absence of an anteromedial tuber of the proximal end, a teardrop-shaped proximal outline, and a fourth trochanter that is not confluent with the proximal head. Osteohistological analyses of PEFO 45274 reveal a cortex comprising low vascularity, parallel-fibered bone composed of primary osteons that lacks a hatching line and any lines of arrested growth. We interpret PEFO 45274 as a slow-growing, post-hatching individual of less than 1 year of age. Surprisingly, osteohistology of some larger phytosaur femora implies faster growth rates in comparison to PEFO 45274 based on the occasional presence of woven bone and overall higher degrees of vascular density, suggesting the ontogenetic shift from rapid-to-slow growth rates might not occur simply or uniformly as expected in Phytosauria and that non-archosaurian archosauriforms may exhibit size-dependent histological characteristics. This study highlights the importance of including osteohistology from multiple body sizes to investigate non-archosaurian archosauriform ancestral growth rates given the phylogenetic position of phytosaurs near the divergence of Archosauria.
Thermodynamics of calcium binding to heparin: Implications of solvation and water structuring for polysaccharide biofunctions
Knight, Brenna M.; Gallagher, Connor M. B.; Schulz, Michael D.; Edgar, Kevin J.; McNaul, Caylyn D.; McCutchin, Christina A.; Dove, Patricia M. (National Academy of Sciences, 2025-08-26)
Heparin sulfates are found in all animal tissues and have essential roles in living systems. This family of biomacromolecules modulates binding to calcium ions (Ca²⁺) in low free energy reactions that influence biochemical processes from cell signaling and anticoagulant efficacy to biomineralization. Despite their ubiquity, the thermodynamic basis for how heparans and similarly functionalized biomolecules regulate Ca²⁺ interactions is not yet established. Using heparosan (Control) and heparins with different positions of sulfate groups, we quantify how SO₃⁻ and COO⁻ content and SO₃⁻ position modulate Ca²⁺ binding by isothermal titration calorimetry. The free energy of all heparin-Ca²⁺ interactions (ΔGrxn) is dominated by entropic contributions due to favorable water release from polar, hydrophilic groups. Heparin with both sulfate esters (O-SO₃⁻) and sulfamides (N-SO₃⁻) has the strongest binding to Ca²⁺ compared to heparosan and to heparin with only O-SO₃⁻ groups (~3X). By linking Ca²⁺ binding thermodynamics to measurements of the interfacial energy for calcite (CaCO₃) crystallization onto polysaccharides, we show molecule-specific differences in nucleation rate can be explained by differences in water structuring during Ca²⁺ interactions. A large entropic term (-TΔSrxn) upon Ca²⁺–polysaccharide binding correlates with high interfacial energy to CaCO₃ nucleation. Combining our measurements with literature values indicates many Ca²⁺–polysaccharide interactions have a shared thermodynamic signature. The resulting enthalpy–entropy compensation relationship suggests these interactions are generally dominated by water restructuring involving few conformational changes, distinct from Ca²⁺–protein binding. Our findings quantify the thermodynamic origins of heparin-specific interactions with Ca²⁺ and demonstrate the contributions of solvation and functional group position during biomacromolecule-mediated ion regulation.
Sinking Airports: A Glance at the State of US Transport Infrastructure
Dasho, Oluwaseyi; Shirzaei, Manoochehr (American Geophysical Union, 2025-07-28)
Land subsidence poses a growing challenge to the operational safety and structural integrity of global air transport infrastructure. This study assesses the impact of differential land subsidence on airport runways using cutting‐edge Interferometric Synthetic Aperture Radar (InSAR) data across 15 major U.S. airports, providing an estimate of potential foundational damage caused by settlement due to natural and anthropogenic factors. Our findings show San Francisco International Airport experiences the fastest subsidence rate of 9.2 ± 0.2 mm/year, while Los Angeles International Airport has the slowest subsidence rate of 2.0 ± 0.2 mm/year. While 96.1% of runway areas fall under low damage risk, 3.9% are at medium to veryhigh (VH) risk, with 3.5 million m2 exposed to subsidence rates exceeding 5 mm/year and 13,950 m2 classified as being at high to VH damage risk. Although no accidents have been directly linked to subsidence, increasing maintenance costs underscore the need for proactive monitoring. InSAR provides a near real‐time, costeffective solution for detecting infrastructure vulnerabilities, offering a non‐intrusive approach to enhancing airport resilience and operational safety.
Insights into the in-situ degradation and fragmentation of macroplastics in a low-order riverine system
Gray, Austin D.; Gore, Beija; Gaesser, Megan; Sequeira, Luisana Rodriguez; Thibodeau, Tessa; Montgomery, Allison; Purvis, Sam; Ouimet, Kathryn; Dura, Tina; Mayer, Kathleen (Oxford University Press, 2025-05)
Inland riverine systems are major conduits of microplastics to coastal environments. Plastic materials that pass through riverine systems are subjected to various degradation processes that facilitate their fragmentation into microplastics (MPs). Low-order streams, a critical yet understudied part of river networks, significantly influence the fate and transport of MPs. Here, we investigate the in situ degradation of common macroplastic polymers (e.g., low-density polyethylene, polyethylene terephthalate, and polystyrene) and their fragmentation into MPs in urban and forested streams. We deployed macroplastic items and a natural biodegradable polymer (cellulose) into a stream habitat for 52 weeks. We found that regardless of stream type (forested or urban), macroplastic polymers produced MPs in two weeks, with polystyrene having the highest fragmentation rate (8 particles/week). We explored several degradation indices (carboxyl index, hydroxyl index, and vinyl index), which revealed that photooxidation played a role in macroplastic degradation over time. Another driver of degradation was biofilm formation observed on the surface of all items, mainly composed of diatoms. Lastly, we found that field-aged macroplastics can leach plastic-derived dissolved organic. Our study narrows the knowledge gap regarding MP degradation and fragmentation in freshwater by providing real-time in situ data on the rate of polymer fragmentation in a low-order riverine system.
Land subsidence risk to infrastructure in US metropolises
Ohenhen, Leonard O.; Zhai, Guang; Lucy, Jonathan; Werth, Susanna; Carlson, Grace; Khorrami, Mohammad; Onyike, Florence; Sadhasivam, Nitheshnirmal; Tiwari, Ashutosh; Ghobadi-Far, Khosro; Sherpa, Sonam F.; Lee, Jui-Chi; Zehsaz, Sonia; Shirzaei, Manoochehr (Springer Nature, 2025-05-08)
Land subsidence is a slow-moving hazard with adverse environmental and socioeconomic consequences worldwide. While often considered solely a coastal hazard due to relative sea-level rise, subsidence also threatens inland urban areas, causing increased flood risks, structural damage and transportation disruptions. However, spatially dense subsidence rates that capture granular variations at high spatial density are often lacking, hindering assessment of associated infrastructure risks. Here we use space geodetic measurements from 2015 to 2021 to create high-resolution maps of subsidence rates for the 28 most populous US cities. We estimate that at least 20% of the urban area is sinking in all cities, mainly due to groundwater extraction, affecting ~34 million people. Additionally, more than 29,000 buildings are located in high and very high damage risk areas, indicating a greater likelihood of infrastructure damage. These datasets and information are crucial for developing ad hoc policies to adapt urban centers to these complex environmental challenges.
Increased flood exposure in the Pacific Northwest following earthquake-driven subsidence and sea-level rise
Dura, Tina; Chilton, William; Small, David; Garner, Andra J.; Hawkes, Andrea; Melgar, Diego; Engelhart, Simon E.; Staisch, Lydia M.; Witter, Robert C.; Nelson, Alan R.; Kelsey, Harvey M.; Allan, Jonathan C.; Bruce, David; DePaolis, Jessica; Priddy, Michael; Briggs, Richard W.; Weiss, Robert; La Selle, SeanPaul; Willis, Michael; Horton, Benjamin P. (2025-05)
Climate-driven sea-level rise is increasing the frequency of coastal flooding worldwide, exacerbated locally by factors like land subsidence from groundwater and resource extraction. However, a process rarely considered in future sea-level rise scenarios is sudden (over minutes) land subsidence associated with great (>M8) earthquakes, which can exceed 1 m. Along the Washington, Oregon, and northern California coasts, the next great Cascadia subduction zone earthquake could cause up to 2 m of sudden coastal subsidence, dramatically raising sea level, expanding floodplains, and increasing the flood risk to local communities. Here, we quantify the potential expansion of the 1% floodplain (i.e., the area with an annual flood risk of 1%) under low (~0.5 m), medium (~1 m), and high (~2 m) earthquake-driven subsidence scenarios at 24 Cascadia estuaries. If a great earthquake occurred today, floodplains could expand by 90 km² (low), 160 km² (medium), or 300 km² (high subsidence), more than doubling the flooding exposure of residents, structures, and roads under the high subsidence scenario. By 2100, when climate-driven sea-level rise will compound the hazard, a great earthquake could expand floodplains by 170 km² (low), 240 km² (medium), or 370 km² (high subsidence), more than tripling the flooding exposure of residents, structures, and roads under the high subsidence scenario compared to the 2023 floodplain. Our findings can support decision-makers and coastal communities along the Cascadia subduction zone as they prepare for compound hazards from the earthquake cycle and climate-driven sea-level rise and provide critical insights for tectonically active coastlines globally.
Estimating Wind Direction and Wind Speed Over Lakes With Surface Water Ocean Topography and Sentinel‐1 Satellite Observations
McQuillan, Katie A.; Allen, George H.; Fayne, Jessica; Gao, Huilin; Wang, Jida (American Geophysical Union, 2025-03-25)
Wind at the water‐air interface is an important driver of hydrologic and biogeochemical processes in lakes. Satellite synthetic aperture radar (SAR) is commonly used over the ocean to retrieve wind fields using backscatter coefficients which are sensitive to wind‐driven surface water roughness; however, its application to lakes has been largely unexplored. Here we assess the utility of SAR to retrieve wind fields specifically for lakes. We estimated wind direction from SAR backscatter using the Modified Local Gradient method for Surface Water Ocean Topography (SWOT) and Sentinel‐1 data. The estimated wind direction was then used as an input into a C‐band geophysical modeling function (GMF) to invert wind speed from Sentinel‐1 data. Comparisons between SWOT backscatter and in situ wind speeds were used to provide a foundation for understanding how SWOT could be used to study wind speeds. Using buoy data for validation, we found wind direction (1 km) mean absolute error (MAE) ranged from 31° to 40° for Sentinel‐1 and 28° to 38° for SWOT. Sentinel‐1 wind speed (100 m) MAE ranged from 1.05 to 2.09 m/s. These retrievals were more accurate and at higher resolution compared to global reanalysis dataset ERA5 (0.25°), with wind direction MAE from 23° to 50° and wind speed MAE from 1.49 to 2.35 m/s. SWOT backscatter sensitivity to wind speed depended on incidence angle, and demonstrated utility for developing a GMF for lakes. These methods could be used to better understand wind dynamics globally, especially over small lakes and in data poor regions.
Elucidating the role of InGaAs and InAlAs buffers on carrier dynamics of tensile strained Ge double heterostructures
Bhattacharya, Shuvodip; Johnston, Steven W.; Bodnar, Robert J.; Hudait, Mantu K. (ACS, 2024-06-06)
Extensive research efforts of strained germanium (Ge) are currently underway due to its unique properties, namely, (i) possibility of band gap and strain engineering to achieve a direct band gap, thus exhibiting superior radiative properties, and (ii) higher electron and hole mobilities than Si for upcoming technology nodes. Realizing lasing structures is vital to leveraging the benefits of tensile-strained Ge (ε-Ge). Here, we use a combination of different analytical tools to elucidate the effect of the underlying InGaAs/InAlAs and InGaAs overlaying heterostructures on the material quality and strain state of ε-Ge grown by molecular beam epitaxy. Using X-ray analysis, we show the constancy of tensile strain in sub-50 nm ε-Ge in a quantum-well (QW) heterostructure. Further, effective carrier lifetime using photoconductive decay as a function of buffer type exhibited a high (low) defect-limited carrier lifetime of ∼68 ns (∼13 ns) in 0.61% (0.66%) ε-Ge grown on an InGaAs (InAlAs) buffer. These results correspond well with the measured surface roughness of 1.289 nm (6.303 nm), consistent with the surface effect of the ε-Ge/III–V heterointerface. Furthermore, a reasonably high effective lifetime of ∼78 ns is demonstrated in a QW of ∼30 nm 1.6% ε-Ge, a moderate reduction from ∼99 ns in uncapped ε-Ge, alluding to the surface effect of the overlying heterointerface. Thus, the above results highlight the prime quality of ε-Ge that can be achieved via III–V heteroepitaxy and paves a path for integrated Ge photonics.

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