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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

At least 883 records · Page 49Linked to original sources

USGS2026

A mid-Holocene age for Monte Verde challenges the timeline of human colonization of South America

Our understanding of the timing of the human colonization of South America has been anchored by the Monte Verde II site in Chile, reported to date to ~14,500 years before the present (B.P.) and regarded as one of the most secure pre-Clovis archeological sites. We report the first independent investigation of Monte Verde in the nearly 50 years since initial excavations. We argue that radiocarbon and luminescence dates from alluvial exposures, in combination with the identification of a tephra dated to 11,000 years B.P. stratigraphically underlying the archaeological component, suggest that Monte Verde cannot be older than the Middle Holocene (8200 to 4200 years B.P.). With colonization no longer anchored by Monte Verde, our revised chronology supports a more recent date of human arrival to South America.

Monte Verde II↗

USGS2026

Bottom-up characterization of geologic methane emissions in the San Juan Basin in the southwestern USA

Methane is a potent greenhouse gas that plays an important role in atmospheric chemistry and global warming. The current global methane budget has large uncertainties, and a better understanding of the budget would help to guide strategies for reducing anthropogenic emissions to fight climate change. Natural geologic methane emissions are a particularly poorly constrained source, with top-down estimates from 14 C in ice cores suggesting much lower geologic emissions than bottom-up scaling of direct flux measurements. Our study aims to contribute to resolving this discrepancy through improved bottom-up characterization of geologic methane seepage in the San Juan Basin in southwestern Colorado and northwestern New Mexico, USA. We performed 983 new flux chamber measurements in this basin during summer 2022 and winter 2023 field campaigns. Our results, in combination with prior measurements, suggest that natural seepage in the San Juan Basin only occurs on or near the Fruitland coal outcrop. Specifically, our new measurements confirm previous measurements of seepage along the northwestern exposure of the Fruitland outcrop in Colorado (a known hydrodynamic overpressure region) and for the first time, identified seepage locations along the southernmost Fruitland outcrop exposure in New Mexico, in association with a coal cleat and a fault. Overall, seepage along the Fruitland coal outcrop is heterogeneously distributed, with both positive and negative (interpreted as microbial soil sink) methane fluxes. Features that are hypothesized to be predictive of seepage (e.g., faults) were not associated with positive methane fluxes in areas outside of the Fruitland outcrop. Our best estimate for total geologic methane seepage in the San Juan Basin from spatial interpolation and statistical upscaling is approximately 0.14 Tg CH 4 /yr, with a range from 0.029 to 0.48 Tg CH 4 /yr. This best-estimate value is lower than a previous bottom-up estimate from a gridded seepage inventory, but higher than a previous top-down estimate.

Colorado, New Mexico↗

USGS2026

Constraining source and path effects of large magnitude earthquakes using ground motion simulations

The purpose of this study is to use ground‐motion simulations to investigate ways in which source and path effects for large‐magnitude earthquakes can be represented in nonergodic ground‐motion models (GMMs). To achieve this, we designed a ground‐motion study in the San Francisco Bay Area that includes earthquakes with a broad range of magnitudes distributed uniformly on a fault plane, and sites covering a large range of rupture distances and azimuths. After running a large suite of kinematic simulations (magnitude 4–7), we then develop a nonergodic GMM with the simulated data. We find that trends in the within‐site residuals are affected significantly by the earthquake radiation pattern, rupture directivity, and slip patterns. Next, we modify an existing rupture directivity model to fit and remove the observed radiation pattern and rupture directivity from the residuals. We also minimize the contributions of slip patterns by averaging the within‐site residuals among multiple source realizations. Finally, after removing the source effects from the within‐site residuals, we compare the path effects computed with different magnitude groups using two approaches. The first approach only considers the small events that have the same shortest path to a site as the large events, whereas the second approach considers all small events on the fault plane. The results indicate that it is difficult to satisfactorily approximate the path effects of large events with those of small events using either approach, at least in the case of simulations.

California↗

USGS2026

Earthquake rupture arrest from depth‐dependent frictional stability on the Pütürge segment of the East Anatolian Fault Zone, Türkiye (Turkey)

Determining why earthquake ruptures stop is a central challenge in earthquake science and seismic hazard assessment. The Pütürge segment of the East Anatolian Fault Zone, Türkiye, exhibits shallow creep (<∼3 km depth) yet hosts M > 6.5 earthquake ruptures at greater depth. Here, we evaluate whether variations in frictional stability along this segment aided arrest of the 2020 M 6.7 Elaziğ and 2023 M 7.8 Pazarcık earthquake ruptures. Analysis of Sentinel‐1 Synthetic Aperture Radar imagery indicates the 2023 M 7.8 rupture propagated laterally into a metamorphic massif within the Pütürge segment, where slip rapidly decayed below detection limits. Creepmeters along this segment recorded no significant surface afterslip (<3 mm) in the following year. To investigate this fault‐slip behavior, we conducted triaxial friction experiments on Pütürge fault gouge sampled from an outcrop exposure. The gouge, composed primarily of muscovite, quartz, and calcite, is velocity strengthening at conditions approximating 0–2.5 km depth and velocity weakening at 4–5 km depth. This transition to velocity‐weakening friction is associated with enhanced comminution and shear localization observed microstructurally. Our results suggest that depth‐dependent frictional stability of the Pütürge fault segment facilitates rupture nucleation and propagation at depth while maintaining rupture‐arresting behavior near Earth’s surface.

Pütürge segment of the East Anatolian Fault Zone↗

USGS2026

Distribution and abundance of Least Bell’s Vireos ( Vireo bellii pusillus ), Southwestern Willow Flycatchers ( Empidonax traillii extimus ), and Coastal California Gnatcatchers ( Polioptila californica californica ) at the Carbon Canyon Dam, Orange County, California—2025 data summary

Executive Summary We surveyed for Least Bell’s Vireos ( Vireo bellii pusillus ; vireo), Southwestern Willow Flycatchers ( Empidonax traillii extimus ; flycatcher), and Coastal California Gnatcatchers ( Polioptila californica californica ; gnatcatcher) at the Carbon Canyon Dam study area near Brea, California, in 2025. Four gnatcatcher and vireo surveys were completed between April 22 and June 25, 2025, and three flycatcher surveys were completed between May 15 and June 25, 2025. We detected 14 territorial male vireos, 12 of which were paired. We also detected a transient vireo. Juvenile vireos were observed in two territories during surveys. Of the five vireo nests incidentally located during surveys, three were parasitized by Brown-headed Cowbirds ( Molothrus ater ). Vireos were reported in four habitat types: (1) mixed willow riparian, (2) riparian scrub, (3) upland, and (4) non-native vegetation. The dominant tree species in vireo territories was Goodding’s black willow ( Salix gooddingii ). Most vireo territories (12) were in habitat with greater than 50-percent native vegetation. The most common exotic species in vireo territories was poison hemlock ( Conium maculatum ). No flycatchers or gnatcatchers were observed during surveys.

California↗

USGS2026

Southwestern Willow Flycatcher ( Empidonax traillii extimus ) surveys at the city of Carlsbad Preserve, San Diego County, California—2025 data summary

Executive Summary We surveyed for Southwestern Willow Flycatchers ( Empidonax traillii extimus ; flycatcher) at five survey areas within the City of Carlsbad Preserve, Carlsbad, California, in 2025. Three flycatcher surveys were completed between May 16 and June 30, 2025. One transient flycatcher was observed at the Lake Calavera survey area in the City of Carlsbad Preserve in 2025.

California↗

USGS2026

Investigation of fish communities in natural channel sections of the Mohawk River, New York

Little is known about the natural resources in the natural channel sections of the Mohawk River between Rome and Frankfort, New York, where the river channel runs separately from and parallel to the Erie Canal. This river section runs through multiple locations that are listed as active remediation sites under New York’s Inactive Hazardous Waste Disposal Site Program and has negligible public or commercial access. As a result, there is minimal recreational usage of this river section, and efforts to conduct biological sampling have been limited. To better understand the composition of fish communities and contaminant concentrations in the natural channel of the Mohawk River, the U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, sampled resident fish in the 34-kilometer section from the mouth of Oriskany Creek downstream to Frankfort. Fish communities were sampled using boat electrofishing during 2021, 2023, and 2024 across multiple reaches within this section. These data were used to estimate species richness (number of species), relative abundance and biomass (catch rates), population size structure (distribution of lengths), and fish condition (a proxy for health). Some gamefish specimens were also analyzed to determine contaminant concentrations in fish tissue. A total of 1,531 individual fish and 38 fish species were captured across all surveys. Seventeen of the 38 (45 percent) species were classified as native to the Mohawk River watershed, whereas 21 of the 38 (55 percent) species were classified as nonnative. Some popular gamefish species such as largemouth bass ( Micropterus salmoides ) and smallmouth bass ( Micropterus dolomieu ) were abundant in most reaches, whereas others such as walleye ( Sander vitreus ) and northern pike ( Esox lucius ) were found sporadically. Only one round goby ( Neogobius melanostomus ) was captured, indicating that this high-profile invasive species remains uncommon in this habitat. A backwater reach had the greatest relative abundance and condition of many species. This indicates connected lentic habitats such as oxbows and backwaters may be important nursery and refuge areas in the aquatic ecosystem. Polychlorinated biphenyl (PCB) concentrations in fish tissue were highly elevated relative to the New York State Department of Health (NYSDOH) fish consumption “don’t eat” advisory guideline. Some specimens exceeded the guideline by an order of magnitude or more, particularly those from a localized area downstream from the Utica Harbor Dam. Concentrations of perfluorooctanesulfonic acid (PFOS) often approached the NYSDOH “don’t eat” consumption guideline but only one sample exceeded the guideline. Concentrations of other contaminants such as mercury and pesticides were consistently measured at less than the “don’t eat” consumption guidelines. These data indicate PCBs remain the primary contaminant of concern in the natural channel of the Mohawk River and are readily bioaccumulating in aquatic organisms despite prior remediation measures. Taken together, the findings in this report are intended to inform future decisions related to fisheries management, public access, recreational usage, and fish consumption advisories.

New York↗

USGS2026

Moose indifferent to canopy loss from forest disturbance by bark beetles

Conifer forests have experienced widespread disturbance following the infestation of bark beetles ( Dendroctonus spp.). Tree mortality and resulting canopy loss have altered forest composition in ways that could affect moose ( Alces alces ), including potential benefits from increased understory forage and drawbacks through the loss of refuge from heat and deep snow. We examined the behavioral response of moose to beetle-killed forest, comparing resource selection before (2005–2006) and after (2015–2017) disturbance in southeast Wyoming, USA. To evaluate selection, we created a land cover classification layer at 0.5-m resolution using machine learning to delineate dead conifers, as well as aspen and willows that were underrepresented in existing land cover products. By measuring resource selection in a fractional cover framework, we found that moose showed strikingly similar resource selection before and after beetle disturbance. Moose during both periods selected willows and aspen while avoiding conifer forest and shrubs throughout the year. Moose in the post-beetle periods avoided conifer forest more strongly the more conifer forest made up their home range. The same pattern emerged for beetle-killed conifer: the more beetle-kill in a home range, the stronger the avoidance of beetle-kill. Our findings indicate that forest disturbance caused by bark beetles does not appreciably alter habitat quality for moose, and moose continue to employ similar patterns of resource selection regardless of forest changes in the early stages of the post-beetle infestation. Our work supports the importance of riparian and deciduous land cover in sustaining moose populations in the face of widespread forest disturbances.

Wyoming↗

USGS2026

Behavioral shifts mask the success of legislation and outreach for endangered species recovery

A fundamental challenge in conservation is assessing the efficacy of recovery actions to optimize endangered species management. Considerable recent attention has focused on effective measures to counter the endangerment of avian scavengers, which have declined worldwide, primarily due to poisoning. One iconic example is efforts to recover the critically endangered California condor ( Gymnogyps californianus ), whose leading cause of death is poisoning from ingesting lead-based ammunition in carcasses. Despite enormous resources expended in California, USA, including implementation of public outreach campaigns and two legislative bans on lead ammunition, lead-related mortality of condors has increased. Here we show that two types of behavioral shifts explain the observed increases in condor lead exposure: wilder foraging and ranging by condors and increased shooting of wild pigs ( Sus scrofa ) by humans. After accounting for these trends, we show that both lead ammunition bans and public outreach efforts have significantly reduced condor blood lead levels in California, lowering mortality. Our analyses uncover a dynamic in which changing ecological conditions mask the true efficacy of legislation and outreach. Given rapid global change, such dynamics are likely operating in many settings, underscoring the importance of comprehensive evaluations of recovery actions, which can be obscured by shifting behaviors and threats.

Baja California, California↗

USGS2026

Deep critical zone controls on shallow landslides

The deep critical zone (CZ) has long been recognized for its importance in influencing shallow landslides but was not considered feasible to include in slope stability models at the watershed scale. In this study, we demonstrate that simple approximations of the CZ in a fully coupled hydrologic and soil slope stability model can effectively capture the location, timing, and likely size of shallow landslides. To achieve this, we use coupled, process-based models that incorporate the effects of 1) deep CZ structures, 2) three-dimensional transient hydrology, and 3) multidimensional slope stability, calibrated with data from an intensively monitored field site. Our results show that the hydrologically active deep CZ guides groundwater flow, influencing where it drains from or exfiltrates to the soil mantle, producing distinct patterns of soil saturation and seepage forces at the soil-bedrock boundary. Deep conductive weathered critical zone drains the soil mantle, reducing the likelihood of destabilizing pore pressures, while the downslope thinning of the CZ forces groundwater to the surface. This creates localized instability and a tendency for similar-sized landslides across the landscape. In contrast, the absence of conductive weathered bedrock results in more widespread destabilizing pore pressures, leading to larger landslides and the likelihood of landslides earlier in a storm than in landscapes underlain by a deep CZ. Our findings suggest that first-order variations of deep CZ can provide physical explanations for variations observed in the susceptibility, magnitude, and timing of shallow landslides, and that CZ structure may be inferred from patterns and timing of landsliding.

Proceedings of the National Academy of Sciences↗

USGS2026

Moving toward a more human-oriented analysis of urban heat: Examining differences of heat exposure intensity at busy commuting locations

Examining urban thermal environments has become a critical area of research spanning epidemiology, urban planning, and ecology. While traditional metrics like air temperature ( T air ) and satellite-derived surface temperature dominate urban heat studies, these measures often fail to reflect how people actually experience thermal exposure intensity. More human-oriented metrics, such as mean radiant temperature (MRT), and the wet bulb globe temperature (WBGT), better capture this lived experience, particularly at locations where people are likely to encounter outdoor heat, such as bus stops. Human demographics further complicate heat exposure, as access to cooling resources like trees and greenspaces can vary by neighborhood income. Our study addresses these complications by collecting thermal data across 60 commuting locations in Denver, Colorado in the summer. We evaluate (1) the extent to which more human-oriented metrics capture thermal exposure compared to T air and LST, and (2) how heat exposure varies by neighborhood income levels. We observed that bus stops in low-income neighborhoods had an MRT increase 2.8 °C compared wealthier neighborhoods, and that income-driven differences in MRT and WBGT strongly depended on bus stop aspect. After accounting for solar orientation, differences in MRT increased to as much as 6.3 °C at north-facing stops. Our results suggest tree canopy shade explains some observed heat exposure patterns, with south facing bus stops seeing a MRT and WBGT decrease of 0.42 °C and 0.11 °C from a percent increase in tree canopy. Interestingly, depending on bus stop aspect, nearby buildings can increase MRT and WBGT (facing east), or decrease MRT and WBGT (facing south) If planners aim to address this issue, consideration of bus stops, and land covers configuration may help.

Colorado↗

USGS2026

New constraints on northeast Seattle basin structure from converted seismic waves

The Seattle basin is a deep sedimentary basin in the Seattle–Bellevue, Washington metropolitan area within the Puget Lowland of Washington State. We determine the structure of a portion of the basin and the underlying basement using analysis of P waves converted from direct S incident from below. A deep local crustal event beneath Monroe, about 35 km northeast of Seattle, was recorded by a 100‐station nodal array deployed in 2019. The event produced a variety of coherent seismic phases, including converted waves from the sediment—basement boundary, internal structure within the basin, and additional crustal discontinuities. Using observed Sp converted waves, we apply an adjoint‐based full waveform inversion (FWI) method to determine the amplitude and extent of seismic discontinuities at depth. We find the strongest source of converted waves for this event lies ∼6 to 7 km depth below northern Lake Washington, interpreted to be the local depth to basement rock. The newly imaged shallow basement structure may be part of a deformation zone associated with the Siletzia eastern boundary. Our results highlight the utility of converted seismic waves recorded by a dense array, combined with an FWI method, to illuminate crustal structure.

Washington↗

USGS2026

A three-dimensional geologic framework model of the northern Great Plains region of Montana, North Dakota, South Dakota, and Wyoming, USA

This report presents a new three-dimensional geologic framework model (GFM) of the northern Great Plains region, encompassing parts of Montana, North Dakota, South Dakota, and Wyoming. The model provides a regionally consistent, geographic information system (GIS)-ready representation of Phanerozoic sedimentary strata, major fault systems, and Precambrian basement geometry across two sedimentary basins and adjacent uplifts. More than 300,000 geologic and geophysical data inputs were synthesized to model 41 stratigraphic horizons and 47 faults, yielding an internally coherent, sealed-volume interpretation of the subsurface. The modeling workflow developed for this study demonstrates an efficient and scalable approach for constructing basin-to regional-scale GFMs in geologically complex and data-variable settings. Although model fidelity varies with data density and quality, the resulting geometry is broadly consistent with 1:500,000-scale geologic mapping and highlights areas where additional geologic study is most needed. The three-dimensional GFM provides a foundational framework to support groundwater, energy, and mineral resource assessments, and offers a transferable methodology for potential future U.S. Geological Survey efforts to build large-area subsurface models in underexplored regions of the United States.

Montana, North Dakota, South Dakota, Wyoming↗

USGS2026

Urban stormwater treatment using biofiltration—Variable performance across solids, nutrients, major ions, and metals

Urban runoff from streets and parking lots carries pollutants that degrade receiving waters. Green infrastructure, such as biofilters, is increasingly used to treat this runoff by mimicking natural hydrologic processes. The U.S. Geological Survey, in cooperation with the Milwaukee Metropolitan Sewerage District, evaluated a biofilter receiving roadway runoff from an industrial area in Milwaukee, Wisconsin, over a 3-year period (2022–24). Paired inlet and outlet samples were analyzed for changes in runoff volume, peak discharge, and concentrations of solids, nutrients, major ions, and metals. The biofilter reduced runoff volume by 86 percent and peak discharge by 92 percent, with substantial reductions in total suspended solids (99 percent), total phosphorus (86 percent), and particulate metals (greater than 80 percent for most analytes). However, dissolved constituents showed variable performance; dissolved phosphorus and several metals exhibited net export, likely influenced by media composition, redox conditions, and winter road salt inputs. Sodium export, despite stable chloride loads, suggests cation exchange and seasonal release dynamics. These findings highlight limitations of conventional biofilter designs for dissolved pollutants and underscore the need for improved media, vegetation management, and consideration of winter deicing practices.

Wisconsin↗

USGS2026

Unravelling equilibrium shoreline response to waves and sea-level rise: Numerical modelling of laboratory experiments

Knowledge gaps in the physics of shoreline response to the combined action of waves and sea-level rise (SLR) make long-term shoreline projections uncertain. The lack of sufficiently long-term shoreline data partly hinders a better understanding of shoreline change driven by SLR. Thereby, existing formulations related to the equilibrium approach, which states that a beach profile shape equilibrates with its local wave and sea-level conditions, have serious limitations. Recent physical modelling studies provided data of beach profile evolution under changing sea levels in controlled laboratory settings. Here, we bring together and analyze laboratory data from three different physical modelling studies to better understand and predict shoreline response to SLR in the context of equilibrium concept. The data indicate a clear relationship among the analyzed variables, highlighting the importance of accounting for interactions between SLR and incident wave power. To further understand these interactions, and given the limited range of conditions tested in the laboratory, we implement a quasi-2D shoreline change model to generate additional synthetic data. We first calibrate and validate the model to emulate the existing laboratory experiments. The model reproduces multiple laboratory experiments that cover a range of settings, providing confidence in its accuracy. Further work will include the generation of synthetic data obtained by forcing the model with new combinations of SLR and wave conditions to better capture the dependency of shoreline recession on SLR and wave conditions.

Conference Paper↗

USGS2026

Beach nourishment morphodynamics in a high-energy U.S. West Coast environment

Dredged sediment from engineered inlets can be used to nourish coastlines adjacent to these inlets, serving as a beneficial alternative to offshore disposal. Effective strategies for beneficial use of dredged sediment, however, rely on understanding of local sediment transport. A beach nourishment project utilizing dredged sand was carried out at a highly energetic beach north of the Columbia River mouth (Washington, USA). Within two weeks of placement, during a moderately energetic period, a large part of the beach nourishment had eroded. To predict local hydro- and morphodynamics there, a XBeach model was used, validated with field observations of nearshore hydrodynamics and morphology. It showed that while the subaerial nourishment eroded rapidly, it is likely that the sediment is deposited around the inner bar and is still available to the morphological system of Benson Beach. Additionally, model simulations suggest the nourishment provided a buffer against erosion of the local dune system during its presence.

Washington↗

USGS2026

The Global Observation System for Mercury dataset for mercury stable isotope signatures in environmental media

The natural variability in the abundance ratios of stable isotopes of mercury (Hg), which collectively forms its isotopic composition, provides information on Hg sources and biogeochemical pathways. Modern mass spectrometry has allowed for measurement of Hg isotope ratios across atmospheric, aquatic, and terrestrial compartments, often at trace levels. Since realizing the utility of Hg isotope ratios, hundreds of studies have generated a wealth of data that is increasingly challenging to summarize and interpret for individual scientists. Arising as a complimentary initiative under the Global Observation System for Mercury (GOS 4 M) that supports the Minamata Convention on Mercury, we describe the establishment of the iGOS 4 M Hg isotope dataset. In its present form, iGOS 4 M has > 11,000 data entries from 190 studies, which together with metadata on sample type, geographical location, Hg concentration, and other environmental and ecological parameters, provide a long-needed catalogue of knowledge gathered by and for the Hg isotope community. We introduce the structure of iGOS 4 M and a standardization rubric to promote global consistency in measurement and data reporting.

Scientific Data↗

USGS2026

Current and near-future conditions of aquatic spatial data for use in ecological models in the United States

To address increasing demand for ecological models of aquatic species that can inform the management of national freshwater resources, we leveraged manager input to develop suites of environmental data layers characterizing freshwater habitats for the contiguous United States. Using the National Hydrography Dataset, these new data cover lentic and lotic systems under current and near-future environmental conditions. The data include a variety of covariate categories including climate, soil chemistry, land use and land cover, and human modification of the surrounding landscape. The predictor resolution for atmospheric climate predictors was the lake (wetland) or stream reach, and, for the terrestrial proxies, the subwatershed (HUC12) surrounding the lake or stream reach was chosen to capture the relevant land features surrounding the habitat. Future land use, land cover and streamflow predictions were included from present to mid-century. These data are available for the development of freshwater ecological models in the contiguous United States for a variety of applications, including species distribution modeling and exploring change in spatially diverse aquatic systems in time.

contiguous United States↗