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USGS2026

Understanding the resource potential of natural hydrogen on Earth: Scientific gaps, uncertainties and recommendations

A comprehensive scientific research roadmap is essential to bridge knowledge gaps and deepen the understanding of key geological, geochemical, and geophysical aspects of natural hydrogen (H 2 ) as a potential new energy resource. This paper reviews major scientific uncertainties on natural H 2 , suggesting research priorities, as a guide for defining exploration strategies, techniques, and data interpretation. The uncertainties concern all phases of the natural H 2 cycle, from generation (source rocks) through migration (advection and diffusion) and accumulation (reservoir and cap rocks) to the application and interpretation of subsurface and surface geochemical and geophysical exploration techniques. Understanding H 2 sources and generation rates (the amount of H 2 generated by a given volume of rock over time) is crucial for determining whether a geological H 2 system operates as a short-term dynamic system with rapid H 2 production and release, or as a conventional gas system with long-term accumulations, analogous to petroleum reservoirs. Preliminary estimates for serpentinisation, radiolysis, and organic matter degradation suggest that H 2 generation is not inherently fast, especially for non-hydrothermal continental systems (crystalline basement of shields, ophiolites, peridotite massifs, sedimentary basins), and long-term accumulations, like those of fossil natural gas systems, represent the most likely scenario. The mechanisms of H 2 migration through geological formations require application of fundamental principles of fluid-flow physics, distinguishing advection and diffusion, as well as their forms (from gas-phase, bubble flows to aqueous solutions). Additional studies of H 2 accumulation and retention in subsurface reservoirs could improve understanding of mechanisms of H 2 migration by focusing on the rock fluid-bearing properties and the factors affecting H 2 preservation, such as the presence of cap rocks impermeable to H 2 , pressure conditions, residence times, and microbial or abiotic consumption. Advanced techniques, including reservoir modelling, flow simulations, 3D imaging (micro-CT) of H 2 -bearing rocks, and extraction and analysis of gas occluded in rocks, can provide insights into the stability and potential recoverability of H 2 accumulations. The interpretation of surface exploration techniques, including gas geochemistry, geophysics, and remote sensing, long employed in mineral and energy resource exploration, is now being adapted for natural H 2 studies, but challenges remain in the data interpretation. Distinguishing H 2 seepage due to geological degassing from H 2 produced near the surface by modern microbial processes or artificial sources, such as hammering or drilling for soil-gas sampling, drilling into aquifers, and corrosion in boreholes, is an essential step in exploration. The simple detection of H 2 in soils, even in morphological structures like sub-circular depressions or “fairy circles”, cannot be cursorily interpreted as a signal of natural H 2 seepage from a deep source. A holistic geochemical approach, including isotopic analyses of gases associated with H 2 , is recommended to distinguish among the variety of possible H 2 origins. Observations of H 2 in wells should be interrogated to rule out possible artifacts such as corrosion and drill bit metamorphism. The integration of multiple geophysical methods, including seismic, gravimetric, magnetic, and electro-magnetic surveys, is recommended to mitigate interpretation ambiguities regarding the structure of a subsurface H 2 system (source and reservoir rocks, including fluid and gas storage), due to the non-uniqueness of rock-specific physical properties.

Earth-Science Reviews↗

USGS2021

Effects of sample gear on estuarine nekton assemblage assessments and food web model simulations

Long-term fisheries-independent sampling data inform population status and trends of species-specific biomass and are often used to drive biomass-based food web models such as the Comprehensive Aquatic Systems Model (CASM). Indicators such as total biomass and mean trophic level derived from these data and from CASM outputs inform management and facilitate assessments of on-going and predicted coastal change and restoration activities on fisheries, but rely on consistent sampling to enable comparisons across space and time. Changes in coastal estuarine gradients, combined with the availability of new sampling technologies, highlight a need to assess the potential consequences of changing sampling technologies on fisheries data and the cascading impact on model outputs. In Louisiana, USA, CASM models are used to inform coastal restoration projects, relying on 40 years of fisheries-independent data derived from 50′ seine sampling. However, alternative use of electrofishers as a sampling method has been proposed to replace the seine sampling. In this study, we examine data from concurrent seine and electrofisher sampling in Barataria Basin, Louisiana, and compare biomass, assemblage data and CASM outputs related to species biomass, food web structure and energy cycling. In a paired comparison of data in 2018–2019, the electrofisher captured higher total catch and diversity compared to the seine. The electrofisher samples were dominated by shrimp (grass, white, brown) and larger bodied fish, while seine samples were dominated by smaller-bodied fish (i.e., anchovy, menhaden). Ecosystem indicators derived from running the CASM using biomass data from seine and electrofisher sampling separately in two different simulation exercises provide contrasting results. In Simulation Exercise 1, the use of different datasets (long-term CASM calibration, 2018–2019 seine, 2018–2019 electrofisher) to initialize the CASM biomasses did not result in large or long-running changes in the simulated biomasses over time. In contrast, in Simulation Exercise 2, CASM model outputs using adjusted gear ratios indicated changes in biomass structure when using electrofisher data, with a doubling of total food web biomass due to the increased shrimp count, and a 13% increase in total energy flow through the food web. Conversions based on area and gear efficiency for overall catch may be useful in maintaining the continuity of historical data. However, differences in species-specific catch due to gear selectivity could have large consequences for constructing and calibrating fish and ecosystem models and remain difficult to reconcile. These differences in assemblages, and estimated biomasses for key food web species, suggest careful consideration in changing gears.

Louisiana↗

USGS2022

Stochastic agent-based model for predicting turbine-scale raptor movements during updraft-subsidized directional flights

Rapid expansion of wind energy development across the world has highlighted the need to better understand turbine-caused avian mortality. The risk to golden eagles ( Aquila chrysaetos ) is of particular concern due to their small population size and conservation status. Golden eagles subsidize their flight in part by soaring in orographic updrafts, which can place them in conflict with wind turbines utilizing the same low-altitude wind resource. Understanding the behavior of soaring raptors in varying atmospheric conditions can therefore be relevant to predicting and mitigating their risk of collision. We present a predictive movement model that simulates individual paths of golden eagles during directional flight (such as migration) that is subsidized by orographic updraft. We modeled eagles in a 50 km by 50 km study area in Wyoming containing three wind power plants with documented golden eagle collisions with turbines. The movement model is applicable to any region where ground elevation is known at turbine scale ( < "> < 50 m) and wind conditions are known at facility scale ( < "> < 3 km). For a given set of atmospheric conditions, the model simulates movements of thousands of orographic soaring eagles to produce a density map quantifying the relative probability of eagle presence. We validated the simulated tracks with GPS telemetry data showing four directional tracks made by golden eagles transiting through the area in 2019 and 2020. For each eagle track, validation was performed using the ratio of the model-simulated eagle presence likelihood with uniform eagle presence and the presence computed using directed random-walk movements. We found that the predictive performance of the model was significantly better (likelihood ratio > "> > 1) for low-altitude movements than high-altitude movements that can involve thermal-soaring. We employed the model to produce seasonal presence maps for migrating golden eagles. We found significant turbine-level variations in eagle presence between northerly and southerly migration routes through the study area. Overall, the proposed model offers a generalizable, probabilistic, and predictive tool to assist wind energy developers, ecologists, wildlife managers, and industry consultants in estimating the potential for conflict between soaring birds and wind turbines, thereby reducing the need for site-specific data on golden eagle movements.

Wyoming↗

USGS2023

An agent-based model to quantify energetics, movement and habitat selection of mid-continent mallards in the Mississippi Alluvial Valley

The dynamics of wintering waterfowl populations at the landscape scale are the result of complex interactions of environmental, behavioral and energetic drivers. Agent-based models provide a method to directly link these factors in a spatially explicit framework and allow the emergence of patterns from the aggregation of individual agent actions. We adapted the Spatially-explicit Waterbird Agent-based Model Program (SWAMP), originally developed for waterfowl in central California, to simulate a basin-scale population of mallards ( A. platyrhynchos ) wintering in the Mississippi Alluvial Valley over a four-month period (November–February). Simulated agents move within the landscape, foraging on areas made available based on a probabilistic inundation status, and converting food resources to endogenous energy. The model uses a high-resolution map of eastern Arkansas waterfowl habitats and incorporates a hierarchical habitat selection system that enables mallards to relocate at increasing scales in response to changing food availability. We validated the performance of modeled mallard body condition and behavioral metrics under a range of environmental conditions against expected outcomes derived from empirical data and found that the simulation produced realistic representations of changes in flight distances, energy expenditure, lipid storage, and foraging habitat use in response to depleting food resources over time. We discuss the model's applicability as a tool to quantify waterfowl response to a range of environmental conditions and to evaluate scenarios of landscape composition and configuration in the context of waterfowl population management.

Ecological Modelling↗

USGS2013

The significance of ultra-refracted surface gravity waves on sheltered coasts, with application to San Francisco Bay

Ocean surface gravity waves propagating over shallow bathymetry undergo spatial modification of propagation direction and energy density, commonly due to refraction and shoaling. If the bathymetric variations are significant the waves can undergo changes in their direction of propagation (relative to deepwater) greater than 90° over relatively short spatial scales. We refer to this phenomenon as ultra-refraction. Ultra-refracted swell waves can have a powerful influence on coastal areas that otherwise appear to be sheltered from ocean waves. Through a numerical modeling investigation it is shown that San Francisco Bay, one of the earth's largest and most protected natural harbors, is vulnerable to ultra-refracted ocean waves, particularly southwest incident swell. The flux of wave energy into San Francisco Bay results from wave transformation due to the bathymetry and orientation of the large ebb tidal delta, and deep, narrow channel through the Golden Gate. For example, ultra-refracted swell waves play a critical role in the intermittent closure of the entrance to Crissy Field Marsh, a small restored tidal wetland located on the sheltered north-facing coast approximately 1.5 km east of the Golden Gate Bridge.

California↗

USGS2020

Large-scale erosion driven by intertidal eelgrass loss in an estuarine environment

Seagrasses influence local hydrodynamics by inducing drag on the flow and dampening near-bed velocities and wave energy. When seagrasses are lost, near-bed currents and wave energy can increase, which enhances bottom shear stresses, destabilizes sediment, and promotes suspension and erosion. Though seagrasses are being lost rapidly globally, the magnitude of change in sediment stabilization following ecosystem-wide eelgrass loss has rarely been measured. In this study, we explored the geomorphological changes associated with an unprecedented estuary-wide collapse of a seagrass (eelgrass, Zostera marina ) in Morro Bay, CA, USA. Morro Bay has historically suffered from accelerated sedimentation and accretion. However, following massive eelgrass loss since 2010, over 90% of locations that previously had eelgrass experienced erosion. Elevation losses (erosion) reached 0.50 m in some places (mean loss of 0.10 m) with as much as a 50% decrease (median decrease of 13.6%) in elevation (i.e., increase in depth) compared to pre-decline levels. In comparison, the mouth of the estuary, where eelgrass was largely retained, had only 27.7% of the locations with prior eelgrass experiencing erosion and underwent a mean elevation increase (accretion) of 0.32 m. Thus, the loss of eelgrass appears to have altered dynamics at the seabed and transitioned large regions of the estuary from an environment that promotes deposition and accretion to one that promotes suspension and erosion. Large-scale erosion following seagrass loss may be predictive of future shoreline and coastal habitat changes and is likely to be exacerbated by increased storm surge and sea level rise expected with climate change.

California↗

USGS2011

Risk management in a large-scale CO2 geosequestration pilot project, Illinois, USA

Like most large-scale infrastructure projects, carbon dioxide (CO 2) geological sequestration (GS) projects have multiple success criteria and multiple stakeholders. In this context "risk evaluation" encompasses multiple scales. Yet a risk management program aims to maximize the chance of project success by assessing, monitoring, minimizing all risks in a consistent framework. The 150,000-km2 Illinois Basin underlies much of the state of Illinois, USA, and parts of adjacent Kentucky and Indiana. Its potential for CO2 storage is first-rate among basins in North America, an impression that has been strengthened by early testing of the injection well of the Midwest Geological Sequestration Consortium's (MGSC's) Phase III large scale demonstration project, the Illinois Basin - Decatur Project (IBDP). The IBDP, funded by the U.S. Department of Energy's National Energy Technology Laboratory (NETL), represents a key trial of GS technologies and project-management techniques. Though risks are specific to each site and project, IBDP risk management methodologies provide valuable experience for future GS projects. IBDP views risk as the potential for negative impact to any of these five values: health and safety, environment, financial, advancing the viability and public acceptability of a GS industry, and research. Research goals include monitoring one million metric tonnes of injected CO2 in the subsurface. Risk management responds to the ways in which any values are at risk: for example, monitoring is designed to reduce uncertainties in parameter values that are important for research and system control, and is also designed to provide public assurance. Identified risks are the primary basis for risk-reduction measures: risks linked to uncertainty in geologic parameters guide further characterization work and guide simulations applied to performance evaluation. Formally, industry defines risk (more precisely risk criticality) as the product L*S, the Likelihood multiplied by the Severity of negative impact. L and S are each evaluated on five-point scales, yielding a theoretical spread in risk values of 1 through 25. So defined, these judgment-based values are categorical and ordinal - they do not represent physically measurable quantities, but are nonetheless useful for comparison and therefore decision support. The "risk entities" first evaluated are FEPs - conceptual Features, Events, and Processes based on the list published by Quintessa Ltd. After concrete scenarios are generated based on selected FEPs, scenarios become the critical entities whose associated risks are evaluated and tracked. In IBDP workshops, L and S values for 123 FEPs were generated through expert elicitation. About 30 experts in the project or in GS in general were assigned among six facilitated working groups, and each group was charged to envision risks within a sphere of project operations. Working groups covered FEPs with strong spatial characteristics - such as those related to the injection wellbore and simulated plume footprint - and "nonspatial" FEPs related to finance, regulations, legal, and stakeholder issues. Within these working groups, experts shared information, examined assumptions, refined and extended the FEP list, calibrated responses, and provided initial L and S values by consensus. Individual rankings were collected in a follow-up process via emailed spreadsheets. For each of L and S, three values were collected: Lower Bound, Best Guess, and Upper Bound. The Lower-Upper Bound ranges and the spreads among experts can be interpreted to yield rough confidence measures. Based on experts' responses, FEPs were ranked in terms of their L*S risk levels. FEP rankings were determined from individual (not consensus or averaged) results, thus no high-risk responses were damped out. The higher-risk FEPs were used to generate one or more concrete, well defined risk-bearing scenarios for each FEP. Any FEP scored by any expert as having associated risk of

Conference Paper↗

USGS2011

The path to a successful one-million tonne demonstration of geological sequestration: Characterization, cooperation, and collaboration

The development of the Illinois Basin-Decatur USA test site for a 1 million tonne injection of CO 2 into the Mount Simon Sandstone saline reservoir beginning in 2011 has been a multiphase process requiring a wide array of personnel and resources that began in 2003. The process of regional characterization took two years as part of a Phase I effort focused on the entire Illinois Basin, located in Illinois, Indiana, and Kentucky, USA. Seeking the cooperation of an industrial source of CO 2 and site selection within the Basin took place during Phase II while most of the concurrent research emphasis was on a set of small-scale tests of Enhanced Oil Recovery (EOR) and CO 2 injection into a coal seam. Phase III began the commitment to the 1 million-tonne test site development through the collaboration of the Archer Daniels Midland Company (ADM) who is providing a site, the CO 2 , and developing a compression facility, of Schlumberger Carbon Services who is providing expertise for operations, drilling, geophysics, risk assessment, and reservoir modelling, and of the Illinois State Geological Survey (ISGS) whose geologists and engineers lead the Midwest Geological Sequestration Consortium (MGSC). Communications and outreach has been a collaborative effort of ADM, ISGS and Schlumberger Carbon Services. The Consortium is one of the seven Regional Carbon Sequestration Partnerships, a carbon sequestration research program supported by the National Energy Technology Laboratory of the U.S. Department of Energy.

Illinois↗

USGS2011

Meeting CCS communication challenges head-on: Integrating communications, planning, risk assessment, and project management

The Midwest Geological Sequestration Consortium, Schlumberger Carbon Services, and Archer Daniels Midland has implemented a comprehensive communications plan at the Illinois Basin–Decatur Project (IBDP), a one million metric tonne Carbon Capture and Storage project in Decatur, IL, USA funded by the U.S. Department of Energy’s National Energy Technology Laboratory. The IBDP Communication Plan includes consortium information, funding and disclaimer citations, description of target audiences, media communications guidelines, paper and presentations guidelines, site visit information, crisis communication, on-site photography regulations, and other components. The creation, development, and implementation processes for the IBDP Communication Plan (the Plan) are shared in this paper. New communications challenges, such as how to address add-on research requests, data sharing and management, scope increase, and contract agreements have arisen since the Plan was completed in January 2009, resulting in development of new policies and procedures by project management. Integrating communications planning, risk assessment, and project management ensured that consistent, factual information was developed and incorporated into project planning, and constitutes the basis of public communications. Successful integration has allowed the IBDP to benefit from early identification and mitigation of the potential project risks, which allows more time to effectively deal with unknown and unidentified risks that may arise. Project risks and risks associated with public perception can be managed through careful planning and integration of communication strategies into project management and risk mitigation.

Illinois↗

USGS2026

VegET evapotranspiration for Africa: Continental-scale simulation, multi-product evaluation, and drought assessment

Study region Continental Africa, encompassing diverse climatic zones—tropical, arid, and temperate—and spanning major transboundary river basins such as the Nile, Niger, Congo, Volta, and Zambezi River Basins. The region exhibits pronounced hydroclimatic gradients and heterogeneous land use systems ranging from rainfed croplands and rangelands to dense tropical forests and irrigated schemes. Study focus Actual evapotranspiration (ETa) is a central component of the terrestrial water balance, governing the redistribution of water and energy between the land surface and the atmosphere. Accurate estimation of ETa at continental scale is critical for hydrological monitoring, water resource management, and climate adaptation, as well as for quantifying water, energy, and carbon fluxes that underpin sustainable development. In this study, we applied the agro-hydrologic VegET v2 model to simulate a new, high-resolution, continental-scale ETa dataset for Africa (2000–2021). The model results were benchmarked against four widely used remote sensing-based products—MODIS16 v6.1, SSEBop v6.1, WaPOR v3, and GLEAM v4.1a—across major climate zones, land use types, and River Basins, providing a comprehensive multi-product evaluation of evapotranspiration dynamics across the continent. New hydrological insights for the region Validation against eddy covariance flux tower observations at eight representative sites confirmed that VegET v2 accurately reproduces the seasonal dynamics of observed ETa, achieving a correlation (r) of 0.8 and an RMSE of 25 mm month⁻¹ —accuracy that is comparable to or higher than accuracies of satellite-based products MODIS16, SSEBop, and GLEAM. This study represents one of the first Africa-wide hydrological simulations of ETa, extending the VegET model beyond basin-scale applications. Intercomparisons reveal that VegET aligns closely with MODIS16, SSEBop, and GLEAM in humid and tropical regions (r = 0.80–0.90; RMSE < 20 mm month⁻¹), while greater discrepancies appear in arid and semi-arid zones, where WaPOR tends to overestimate ETa (RMSE ≥ 28 mm month⁻¹). Despite these differences, VegET effectively captures spatial and temporal ETa variability across rainfed croplands, forests, and savannas, supporting its utility in regional water balance assessments, water accounting, and drought monitoring. A key application of VegET v2 is the Evapotranspiration Deficit Index (ETDI), derived by integrating VegET-based ETa with potential evapotranspiration (PET) to quantify water stress. ETDI successfully captured major drought episodes across Africa, including persistent Sahelian and southern African dry spells, the 2020–2021 winter drought in the Maghreb, and the 2018–2019 austral summer drought in southern Africa, while identifying positive anomalies over central Africa indicative of recurrent wetness. These results underscore VegET’s capability as a hydrologically consistent, operational tool for continental ETa monitoring and drought assessment, offering support for basin-scale water balance studies, food security planning, and climate resilience across Africa’s diverse hydrological environments.

Journal of Hydrology: Regional Studies↗

USGS2017

Widespread legacy brine contamination from oil production reduces survival of chorus frog larvae

Advances in drilling techniques have facilitated a rapid increase in hydrocarbon extraction from energy shales, including the Williston Basin in central North America. This area overlaps with the Prairie Pothole Region, a region densely populated with wetlands that provide numerous ecosystem services. Historical (legacy) disposal practices often released saline co-produced waters (brines) with high chloride concentrations, affecting wetland water quality directly or persisting in sediments. Despite the potential threat of brine contamination to aquatic habitats, there has been little research into its ecological effects. We capitalized on a gradient of legacy brine-contaminated wetlands in northeast Montana to conduct laboratory experiments to assess variation in survival of larval Boreal Chorus Frogs ( Pseudacris maculata ) reared on sediments from 3 local wetlands and a control source. To help provide environmental context for the experiment, we also measured chloride concentrations in 6 brine-contaminated wetlands in our study area, including the 2 contaminated sites used for sediment exposures. Survival of frog larvae during 46- and 55-day experiments differed by up to 88% among sediment sources (Site Model) and was negatively correlated with potential chloride exposure (Chloride Model). Five of the 6 contaminated wetlands exceeded the U.S. EPA acute benchmark for chloride in freshwater (860 mg/L) and all exceeded the chronic benchmark (230 mg/L). However, the Wetland Site model explained more variation in survival than the Chloride Model, suggesting that chloride concentration alone does not fully reflect the threat of contamination to aquatic species. Because the profiles of brine-contaminated sediments are complex, further surveys and experiments are needed across a broad range of conditions, especially where restoration or remediation actions have reduced brine-contamination. Information provided by this study can help quantify potential ecological threats and help land managers prioritize conservation strategies as part of responsible and sustainable energy development.

Montana, North Dakota, South Dakota↗

USGS2023

Investigating effects of climate-induced changes in water temperature and diet on mercury concentrations in an Arctic freshwater forage fish

The amount of mercury (Hg) in Arctic lake food webs is, and will continue to be, affected by rapid, ongoing climate change. At warmer temperatures, fish require more energy to sustain growth; changes in their metabolic rates and consuming prey with potentially higher Hg concentrations could result in increased Hg accumulation. To examine the potential implications of climate warming on forage fish Hg accumulation in Arctic lakes, we quantified growth and Hg accumulation in Ninespine Stickleback Pungitius pungitius under different temperature and diet scenarios using bioenergetics models. Four scenarios were considered that examined the role of climate, diet, climate × diet, and climate × diet × elevated prey Hg. As expected, annual fish growth increased with warmer temperatures, but growth rates and Hg accumulation were largely diet dependent. Compared to current growth rates of 0.3 g⋅y −1 , fish growth increased at least 200% for fish consuming energy-dense benthic prey and decreased at least 40% for fish consuming pelagic prey. Compared to baseline levels, the Hg burden per kilocalorie of Ninespine Stickleback declined up to 43% with benthic consumption – indicating strong somatic growth dilution – but no more than 4% with pelagic consumption; elevated prey Hg concentrations led to moderate Hg declines in benthic-foraging fish and Hg increases in pelagic-foraging fish. Bioenergetics models demonstrated the complex interaction of water temperature, growth, prey proportions, and prey Hg concentrations that respond to climate change. Further work is needed to resolve mechanisms and rates linking climate change to Hg availability and uptake in Arctic freshwater systems.

Alaska↗

USGS2014

Fine-grained linings of leveed channels facilitate runout of granular flows

Catastrophic dense granular flows, such as occur in rock avalanches, debris flows and pyroclastic flows, move as fully shearing mixtures that have approximately 60 vol.% solids and tend to segregate to form coarse-grained fronts and leveed channels. Levees restrict spreading of unconfined flows and form as coarse particles that become concentrated in the top of the flow are transported to the front and then advect to the sides in the flow head. Channels from which most material has drained away down slope are commonly lined with fine-grained deposit, widely thought to remain from the tail of the waning flow. We show how segregation in experimental dense flows of carborundum or sand (300–425 μm) mixed with spherical fine ballotini (150–250 μm), on rough slopes of 27–29°, produces fine-grained channel linings that are deposited with the levees, into which they grade laterally. Maximum runout distance is attained with mixtures containing 30–40% sand, just sufficient to segregate and form levees that are adequately robust to restrict the spreading attributable to the low-friction fines. Resin impregnation and serial sectioning of deliberately arrested experimental flows shows how fines-lined levees form from the flow head; the flows create their own stable ‘conduit’ entirely from the front, which in a geophysical context can play an important mechanistic role in facilitating runout. The flow self-organization ensures that low-friction fines at the base of the segregated channel flow shear over fine-grained substrate in the channel, thus reducing frictional energy losses. We propose that in pyroclastic flows and debris flows, which have considerable mobility attributable to pore-fluid pressures, such fine-grained flow-contact zones form similarly and not only reduce frictional energy losses but also reduce flow–substrate permeability so as to enhance pore-fluid pressure retention. Thus the granular flow self-organization that produces fine-grained channel linings can be an important factor in facilitating long runout of catastrophic geophysical flows on the low slopes (few degrees) of depositional fans and aprons around mountains and volcanoes.

Earth and Planetary Science Letters↗

USGS2018

Testing for the ‘predictability’ of dynamically triggered earthquakes in Geysers Geothermal Field

The Geysers geothermal field is well known for being susceptible to dynamic triggering of earthquakes by large distant earthquakes, owing to the introduction of fluids for energy production. Yet, it is unknown if dynamic triggering of earthquakes is ‘predictable’ or whether dynamic triggering could lead to a potential hazard for energy production. In this paper, our goal is to investigate the characteristics of triggering and the physical conditions that promote triggering to determine whether or not triggering is in anyway foreseeable. We find that, at present, triggering in The Geysers is not easily ‘predictable’ in terms of when and where based on observable physical conditions. However, triggered earthquake magnitude positively correlates with peak imparted dynamic stress, and larger dynamic stresses tend to trigger sequences similar to mainshock–aftershock sequences. Thus, we may be able to ‘predict’ what size earthquakes to expect at The Geysers following a large distant earthquake.

California↗

USGS2020

Investigating the effects of broad ion beam milling to sedimentary organic matter: Surface flattening or heat-induced aromatization and condensation?

Previous work has proposed transfer of kinetic heat energy from low-energy broad ion beam (BIB) milling causes thermal alteration of sedimentary organic matter, resulting in increases of organic matter reflectance. Whereas, other studies have suggested the organic matter reflectance increase from BIB milling is due to decreased surface roughness. To test if reflectance increases to sedimentary organic matter (vitrinite) caused by BIB milling were related to molecular aromatization and condensation, Raman and Fourier transform infrared (FTIR) spectroscopies were used to evaluate potential compositional changes in the same vitrinite locations pre- and post-BIB milling. The same locations also were examined by atomic force microscopy (AFM) to determine topographic changes caused by BIB milling (as quantified by the areal root-mean-square roughness parameter S q ). Samples consisted of four medium volatile bituminous coals. A non-aggressive BIB milling approach was used with conditions of 5 min, 4 keV, 15°incline, 360° rotation at 25 rpm and 100% focus (1.5 kV discharge; ∼100 μA). This gentle BIB milling caused vitrinite reflectance (VR o ) increases of 12 to 36% of the original values determined optically before milling (average 26% increase). When molecular proxies from FTIR (A- and C-factor, branching ratio) were plotted against each other for the same vitrinite locations pre- and post-milling, mean data points for each sample generally lie within error of a 1:1 line. Likewise, mean Raman thermal proxy [full-width half maximum of G-band (G-FWHM), Raman band separation (RBS) and D1/G band intensity ratio] values were similar for pre- and post-milled locations, also plotting within error of a 1:1 line. AFM confirms the majority (24 of 36) of pre- and post-ion milled surface pairs were smoother (lower S q values) after BIB milling. These results are interpreted to indicate VR o increase induced by the gentle BIB milling conditions used in this study is an effect of decreased diffuse reflectance due to flatter surfaces, causing more photons to reflect directly back to the detector. Little evidence was observed for molecular aromatization and condensation of vitrinite molecules following BIB milling (with the conditions used). The presence of milling-induced artifacts, including differential milling effects dependent on location and the development of self-organized patterned structures, indicate much work remains in standardization of BIB milling before its promulgation as a routine sample preparation technique for organic petrography. These results provide better understanding of anthropogenic-induced changes to geological samples caused by the now widespread adoption of BIB milling as a disruptive innovation in sample preparation.

Fuel↗

USGS2019

Kinetics of elemental sulfur reduction by petroleum hydrocarbons and the implications for hydrocarbon thermal chemical alteration

Although sulfur-containing compounds are known to play a significant role in the diagenic and catagenic processes that generate oil and gas, relatively little is known about the kinetics of reactions between elemental S and petroleum hydrocarbons. To investigate this subject, a series of closed-system pyrolysis experiments using paraffin, a low-sulfur oil, and a high-sulfur oil with and without elemental S were conducted, and first-order chemical kinetics were fit to the experimental results. The average value for the activation energy required to reduce elemental S to H 2 S and to thermochemically alter higher molecular weight hydrocarbons to methane was calculated to be 193 kJ mol -1 (46 kcal mol -1 ). The results of this study demonstrate that under typical geologic conditions the rate of reduction of elemental S to H 2 S by petroleum hydrocarbons is quite rapid. The maximum time for substantial amounts of elemental S to persist in contact with petroleum hydrocarbons is estimated to be no more than a few million years in cool reservoirs (e.g., <80 °C), and in hotter reservoirs (e.g., >120 °C) the half-life of elemental S may be as short as hundreds of years. Additionally, the presence of elemental S substantially lowers the onset temperature of hydrocarbon thermal chemical alteration (TCA). The activation energy for TCA of a low-sulfur oil to generate methane is estimated to be lowered by 92 kJ mol -1 (22 kcal mol -1 ) due to the presence of elemental sulfur. Consequently, the presence of elemental S in petroleum reservoirs is expected to lower the thermal stability of oil and decrease the maximum depth at which oil occurs within a basin (thermal deadline). The observed acceleration of hydrocarbon TCA is possibly due to organic sulfur compounds (e.g., thiols and sulfides) that form through the reaction of H 2 S or polysulfides with hydrocarbons and subsequently thermally degrade leading to the formation of sulfur radicals that in turn enhance TCA reactions.

Geochimica et Cosmochimica Acta↗

USGS2019

Temperature-dependent variations in mineralogy, major element chemistry and the stable isotopes of boron, lithium and chlorine resulting from hydration of rhyolite glass: Constraints from hydrothermal experiments at 150 to 350°C and 25 MPa

Rhyolite-hosted hydrothermal systems in the continental crust contain valuable energy and mineral resources that make them of special interest across several scientific disciplines. Despite extensive research on these systems, the temperature-dependence of chemical reactions between host rocks and aqueous-rich fluids and the mineralogical transformations resulting from these reactions are not well quantified. To expand our understanding of the controlling processes operating in these systems, we carried out seven laboratory experiments in which rhyolite was reacted with deionized water at 150 °C to 350 °C and 25 MPa. An additional experiment at 200 °C was carried out to examine the effect of dissolved CO 2 on the reactions. The overarching goal of this experimental study was to provide new insights on the temperature-dependence of water-rock interaction in continental hydrothermal systems. We applied a wide range of chemical, isotopic and mineralogical methods to analyze the reacted rhyolite and waters, and the major observations are: (1) the rhyolite progressively hydrates with increasing temperature between 150 °C to a maximum of 8.2 wt% H 2 O at 275 °C; hydration then decreases until 350 °C in conjunction with the destruction of the rhyolite glass and crystallization of secondary mineral phases; (2) the ratio of molecular water (H 2 O m ) to hydroxyl (OH − ) of the water that is dissolved in the reacted rhyolite decreases from ∼7 at 150 °C to ∼4 at 250 °C; (3) the main secondary minerals formed are the zeolite ferrierite (T ≥ 275 °C); biotite, albite and cristobalite mainly form at higher experimental temperatures (T ≥ 300 °C); (4) the reacted waters are nearly saturated with respect to amorphous silica; (5) at temperatures ≥ 275 °C nearly all the chlorine is leached into solution; (6) fluorine leaching from the rhyolite gradually increases between 150 °C and 250 °C, but then gradually decreases at higher temperatures and is incorporated into a secondary mineral phase; (7) dissolved CO 2 in the water enhances alkali metal cation leaching from the rhyolite; and (8) calculated Na-K and silica geothermometer temperatures differ from the experimental temperatures by varying amounts. In addition, apart from some small lithium isotope fractionation at temperatures ≤ 250 °C, the stable isotopes of boron, lithium and chlorine do not fractionate during rhyolite-water reactions, and the stable isotope compositions of these species in the reacted water are similar to those in the reactant rhyolite. These results provide new insights for a broad range of applications, including quantifying processes involving rhyolite glass hydration (obsidian hydration dating, perlite formation and discriminating secondary from magmatic water in rhyolitic matrix-glass of volcanic pyroclasts), for geothermal energy and mineral deposit exploration and for monitoring volcanoes.

Geochimica et Cosmochimica Acta↗

USGS2017

Projected atoll shoreline and run-up changes in response to sea-level rise and varying large wave conditions at Wake and Midway Atolls, Northwestern Hawaiian Islands

Atoll islands are dynamic features that respond to seasonal alterations in wave conditions and sea level. It is unclear how shoreline wave run-up and erosion patterns along these low elevation islands will respond to projected sea-level rise (SLR) and changes in wave climate over the next century, hindering communities' preparation for the future. To elucidate how these processes may respond to climate change, extreme boreal winter and summer wave conditions under future sea-level rise (SLR) and wave climate scenarios were simulated at two atolls, Wake and Midway, using a shallow-water hydrodynamic model. Nearshore wave conditions were used to compute the potential longshore sediment flux along island shorelines via the CERC empirical formula and wave-driven erosion was calculated as the divergence of the longshore drift; run-up and the locations where the run-up exceed the berm elevation were also determined. SLR is projected to predominantly drive future island morphological change and flooding. Seaward shorelines (i.e., ocean fronted shorelines directly facing incident wave energy) were projected to experience greater erosion and flooding with SLR and in hypothetical scenarios where changes to deep water wave directions were altered, as informed by previous climate change forced Pacific wave modeling efforts. These changes caused nearshore waves to become more shore-normal, increasing wave attack along previously protected shorelines. With SLR, leeward shorelines (i.e., an ocean facing shoreline but sheltered from incident wave energy) became more accretive on windward islands and marginally more erosive along leeward islands. These shorelines became more accretionary and subject to more flooding with nearshore waves becoming more shore-normal. Lagoon shorelines demonstrated the greatest SLR-driven increase in erosion and run-up. They exhibited the greatest relative change with increasing wave heights where both erosion and run-up magnitudes increased. Wider reef flat-fronted seaward shorelines became more accretive as all oceanographic forcing parameters increased in magnitude and exhibited large run-up increases following increasing wave heights. Island end shorelines became subject to increased flooding, erosion at Wake, and accretion at Midway with SLR. Under future conditions, windward and leeward islands are projected to become thinner as ocean facing and lagoonal shorelines erode, with leeward islands becoming more elongate. Island shorelines will change dramatically over the next century as SLR and altered wave climates drive new erosional regimes. It is vital to the sustainability of island communities that the relative magnitudes of these effects are addressed when planning for projected future climates.

Midway Atoll, Wake Atoll↗