USGS Science⌕ Search

SEARCH · USGS Science

Results for “Journal of Analytical and Applied Pyrolysis”

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

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

1,688 records · Page 56Linked to original sources
USGS2024

Fish beta diversity associated with hydrologic and anthropogenic disturbance gradients in contrasting stream flow regimes

Understanding the role of hydrologic variation in structuring aquatic communities is crucial for successful conservation and sustainable management of native freshwater biodiversity. Partitioning beta diversity into the additive components of spatial turnover and nestedness can provide insight into the forces driving variability in fish assemblages across stream flow regimes. We examined stream fish beta diversity across hydrologic and anthropogenic disturbance gradients using long-term (1916–2016) site occurrence records ( n = 17,375) encompassing 252 species. We assessed total beta diversity (Sørensen dissimilarity), spatial turnover, and nestedness of fish assemblages in contrasting stream flow regimes across a gradient of decreasing flow stability: groundwater stable ( n = 77), groundwater ( n = 67), groundwater flashy ( n = 175), perennial runoff ( n = 141), runoff flashy ( n = 255), and intermittent ( n = 63) streams. Differences in total beta diversity among the stream flow regimes were driven predominantly (>86 %) by spatial turnover (i.e. species replacement) as opposed to nestedness (i.e. species loss or gain). Total fish beta diversity and spatial turnover were highest in streams with intermediate flow stability (groundwater flashy), while more flow-stable streams (groundwater stable and groundwater) had lower turnover and higher nestedness. Species turnover was also strongly associated with seasonal variation in hydrology across all flow regimes, but these relationships were most evident for assemblages in intermittent streams. Distance-based statistical comparisons showed significant correlations between beta diversity and anthropogenic disturbance variables, including dam density, dam storage volume and water withdrawals in catchments of groundwater stable streams, while hydrologic variables were more strongly correlated with beta diversity in streams with runoff-dominated and flashy flow regimes. The high spatial turnover of species implies that fish conservation actions would benefit from watershed-focused approaches targeting multiple streams with wide spatial distribution, as opposed to simply focusing on preserving sites with the greatest number of species.

Science of the Total Envionrment↗
USGS2026

Multiple-well monitoring site adjacent to the Midway- Sunset and Buena Vista Oil Fields, Kern County, California

Groundwater quality in and around oil fields in the Southern San Joaquin Valley is of interest to many California residents that rely heavily on groundwater for domestic, commercial, and agricultural use. To help assess the effects of historical oil-field activities and natural geologic sources on groundwater near the southwest margins of the Kern County Groundwater Subbasin, a multiple-well monitoring site was installed near the administrative boundary between the Midway-Sunset and Buena Vista Oil Fields in Kern County, California. The installation of the Midway-Sunset Buena Vista multiple-well monitoring site (MSBV) supports regional analysis of the relations of oil and gas sources to groundwater quality by providing information about the geology, hydrology, geophysical properties, and water quality of the alluvial and upper Tulare aquifers in areas where groundwater data were limited. Data collected from the site included drill cuttings, whole core samples, sidewall core samples, mud-gas analysis, borehole geophysical logs, depth to water measurements, and water quality samples. Whole cores were scanned using dual energy computed tomography. Subsamples of selected cores were analyzed for density, porosity, specific retention, and bulk minerology. Thin sections of the subsamples were prepared, photographed, and examined. Two samples were analyzed using scanning electron microscope technology to examine the microporosity of diatomite laden sediment. Instrumentation installed in the wells collect hourly depth to water measurements. Analysis of the data show there is 355 feet of alluvium overlying the Tulare Formation at the well site. The contact between the two formations is an aquitard resulting in a perched aquifer in the alluvium and unconfined aquifer in the Tulare Formation. The alluvium is more heterogenous and finer grained than the Tulare Formation resulting in markedly higher porosity in the alluvium compared to the Tulare Formation. Higher specific retention observed in the alluvium is attributed to the finer grained sediment and greater abundance of reworked diatomite (as represented by opal-CT [cristobalite-tridymite]) compared to the Tulare Formation. Total dissolved solids (TDS) approached or exceeded 10,000 milligrams per liter (mg/L) in the alluvium from approximately 176 to 242 feet below land surface and at the top of the Amnicola clay at approximately 670 feet below land surface within the Tulare Formation. Elevated TDS, chloride, and boron concentrations in the alluvium and on top of the Amnicola clay likely reflect groundwater that is mixed with oil-field water. Water chemistry and modern-aged groundwater in the alluvial monitoring well (MSBV #3) are consistent with the oil-field water in the alluvium being derived from documented historical surface disposal of oil-field water upslope (northwest) of the site. Water chemistry and pre-modern groundwater age in the deeper Tulare monitoring well (MSBV #1) on top of the Amnicola clay are consistent with oil-field fluids derived from upslope natural geologic sources or old oil wells that leak in the subsurface. Shallow groundwater in the Tulare (MSBV #2) is not affected by mixing with oil-field sources.

EarthArXiv↗
USGS1976

Ground magnetic and VLF studies at Midnite uranium mine, Stevens County, Washington

Ground magnetic and E-mode VLF measurements were made at more than 200 stations at the Midnite uranium Mine, Stevens County, Washington. The equipment was found to be light and foolproof, and each set of data was collected in one day, exclusive of surveying and marking the station points. The maps of contoured magnetic and VLF data resembled geologic maps of the area, showing many common features, as well as a few unique features on each map. Each showed some evidence of a small normal fault cutting the region; taken together, the evidence for this fault was judged to be much stronger, so that further structural details were inferred. Because of soil cover and inadequate outcrops, the presence of this fault had hitherto been unsuspected. A target area for further uranium mineralization north of the fault was indicated by this quick, inexpensive geophysical survey. The drilling program which Midnite Mine management had underway at that time had already outlined a mineralized zone in the indicated area.

Washington↗
USGS2024

Bedrock geologic map of the Woodstock quadrangle, Grafton County, New Hampshire

The bedrock geology of the Woodstock 7.5-minute quadrangle consists of highly deformed metasedimentary rocks of the Central Maine trough, including the Silurian Rangeley and Perry Mountain Formations and the Devonian Littleton Formation. The central, northern, and eastern parts of the quadrangle are underlain by the oldest rocks in the area, the Rangeley Formation. In the southwest and south-central part of the quadrangle, metaturbidites of the Perry Mountain Formation and subsequent Littleton Formation overly the Rangeley Formation in a deformed F 1 synform, herein informally called the Bagley Brook basin. The metasedimentary rocks were intruded by widespread syn- to post-tectonic granitoids of the Devonian New Hampshire Plutonic Suite and minor post-metamorphic Jurassic-Cretaceous mafic dikes of the White Mountain Plutonic-Volcanic Suite. The metasedimentary rocks were affected by at least two episodes of deformation in the Devonian Acadian orogeny. The dominant regional foliation is second-generation (S 2 /D 2 ) and formed during the development of sillimanite-muscovite mineral assemblages. Large bodies of the Early Devonian Kinsman Granodiorite intruded the metasedimentary rocks semi-concordantly during D 2 deformation. Dikes of the Late Devonian Concord Granite cut the Kinsman Granodiorite and the metasedimentary rocks and were emplaced either syn- or post-D 2 . The map pattern in the Rangeley Formation is dominated by northeast to northwest trending, moderately to steeply north-dipping F 2 and F 3 folds. Map-scale F 1 folds are defined by the Bagley Brook basin. Previous division of Rangeley Formation stratigraphy in this region into “upper” and “lower” parts was not corroborated by 1:24,000-scale mapping of lithodemic units, and rocks previously mapped as part of the Smalls Falls and Madrid Formations are here reassigned to the Rangeley Formation. Some rocks previously mapped as the lower part of the Littleton Formation are now assigned to the Perry Mountain Formation. The Littleton Formation on this map is approximately equivalent to rocks previously mapped as the upper part of the same formation. Steeply dipping fractures in the quadrangle show a preferred northeast orientation, consistent with subsurface fracture orientations in the well fields near Mirror Lake. Jurassic-Cretaceous mafic dikes and normal faults show preferred northeast orientations, similar to the fractures, suggesting that the extensional stress field that controlled dike orientation during the Mesozoic also produced the dominant brittle fabrics in the area.

New Hampshire↗
USGS2024

Geomorphic map of the Umatilla River corridor, Oregon

This map portrays the distribution of landforms along the Umatilla River in northeastern Oregon and covers a corridor 127 kilometers long from the confluence of the Umatilla River with the Columbia River upstream to Meacham Creek. The map encompasses the valley bottom and extends about 1 kilometer up the adjoining hillslopes. Map data are intended to support water quality and fisheries enhancement efforts pursuant to the First Foods, a resource-management approach that focuses on traditionally gathered foods including water, fish, big game, roots, and berries and calls attention to the reciprocity between people and the foods upon which humans depend. The Umatilla River drains about 6,300 square kilometers on the northwest slope of the Blue Mountains in northeast Oregon. Most of the drainage basin is underlain by Miocene basalt flows of the Columbia River Basalt Group. Younger, weakly lithified, late Miocene and early Pliocene gravel deposits of local origin (for example, McKay Formation) are mapped in a few places. Upland surfaces are mantled with windborne silt (loess) correlative with deposits elsewhere known as the Palouse Formation. Surfaces below an elevation of about 340 meters were inundated repeatedly by large Pleistocene glacial outburst floods, most emanating from glacial Lake Missoula in western Montana. In backflooded areas such as the lower Umatilla River valley, Missoula floods deposited extensive slack-water silt. Areas mapped as open water, active channel and tie channel, flood basin, valley bottom, and modified land constitute the geomorphic floodplain: the area subject to occasional inundation by the Umatilla River. Deposits and landforms within the floodplain are inset into Missoula flood deposits and hence postdate the 20–15-kilo-annum Missoula floods. Some floodplain deposits are no more than a few centuries old, as indicated by substantial erosion and deposition during the Umatilla River flood of February 2020, the largest since systematic measurements began in October 1903. Deposits and landforms of the floodplain are transient features within the longer-term incision of the Umatilla River into mid-Miocene flood basalts and younger gravel of the McKay Formation.

Oregon↗
USGS2025

Protected from Pterygoplichthys? Predicting thermal habitat suitability for nonnative armored catfish in the Suwannee River

Objective Nonnative fishes can modify ecosystems and harm economies when they are introduced to new environments. Climate change is likely to assist the spread and establishment of some nonnative fishes (e.g., warmwater species), but spatiotemporal gaps in water temperature monitoring and modeling may prevent ecologists and managers from forecasting thermal habitat suitability for these taxa. The purpose of this study was to develop a predictive model of winter water temperatures and thermal habitat suitability for two priority nonnative armored catfish, Vermiculated Sailfin Catfish Pterygoplichthys disjunctivus and Orinoco Sailfin Catfish P. multiradiatus , in the Suwannee River, Florida and Georgia. Methods Precipitation- and groundwater-corrected air–water temperature models were developed and evaluated using a model selection procedure to predict water temperatures at four sites in the Suwannee River. These models were chosen because they blend the simplicity of air–water temperature models with the accuracy of hydrometeorological models to create an efficient, economical, management-relevant approach for analyzing and forecasting water temperature. Results Most of the top-performing water temperature models (92%) had precipitation or groundwater corrections to air–water temperature formulations. Projected mean and maximum water temperatures increased as simulated climate change intensified. All four Suwannee River sites studied were projected to be thermally hospitable to the survival of Vermiculated Sailfin Catfish. Lower river sites, noticeably warmer than upper river sites, were conducive to the survival of Orinoco Sailfin Catfish throughout the winter months. The upper river sites were too cold for Orinoco Sailfin Catfish survival in some climate-change scenarios, but the Suwannee River has an abundance of constant-temperature springs that are likely hospitable to Vermiculated Sailfin Catfish and Orinoco Sailfin Catfish throughout the year. Conclusions The findings suggest that winter water temperatures will likely not be a barrier to the survival of Pterygoplichthys catfish in the Suwannee River, amplifying the importance of conservation and management approaches to inhibit their spread and establishment. If the Pterygoplichthys population remains small and isolated and decision makers are able to devote required staff time and resources to managing these species, removal and eradication at local if not broader scales may be reasonable goals. This study provides a water temperature modeling approach that can aid ecologists and managers in prioritizing sites to prevent the introduction, slow the dispersal, eradicate, and control Pterygoplichthys catfish and other nonnative fishes in the Suwannee River and beyond.

Florida, Georgia↗
USGS2025

Metal fingerprints of Eocene rhyolite magmas coincident with Carlin-type gold deposition in Nevada USA

Eocene magmatic systems contemporaneous with world-class Carlin-type Au deposits in Nevada (USA) have been proposed by some researchers as a key ingredient for Au mineralization, though evidence conclusively demonstrating their genetic relationship remains tenuous. This study provides the first direct evidence of the pre-eruptive metal budget of volatile- and metal-charged silicic magmas coincident in time (~41 to 34 Ma) and space (within 5 km) with Carlin-type Au deposits. We characterize the pre-eruptive metal fingerprints of these diverse magmatic systems to assess their potential as sources of metals for Carlin-type Au mineralization. Metal abundances from quartz-hosted melt inclusions (Au, Te, Ag, Sb, Tl, Mo, W, Sn, As, Pb, Co, Cu, Ni, and Zn) characterized in situ by SHRIMP-RG and LA-ICP-MS represent our best (and only) estimates for the pre-eruptive metal budget in these systems. Median metal concentrations are generally within one order of magnitude of average upper crust and average continental rhyolite values. But there are two notable exceptions, with median Au contents extending >1 order of magnitude higher than average upper crust and median Cu contents ranging >1 order of magnitude lower than upper crust. Despite this, melts contain lower Au/Cu (<0.1), Au/Ag (<5), and Au/Tl (<0.3) than most ore-grade Carlin-type rock samples and quartz-hosted fluid inclusions, regardless of their age and timing relative to nearby Carlin-type Au mineralization. The metal fingerprints of these magmatic systems, de-fined both by traditional and multivariate compositional data analysis techniques, are distinct from one another. Yet none are particularly specialized, e.g., high Au/Cu, in terms of being ideal ingredients as postulated by magmatic models for Carlin-type Au mineralization. Magmatic Au contents do not appear to be correlated with rhyolite “flavors” in the way that Cu, Sn, and Nb contents are. Fluid/melt partitioning modeling and magma volume estimates support the idea that a diverse array of non-specialized silicic magmas could feasibly contribute some or potentially all of the Au, Ag, and Cu in Carlin-type systems. The compositional diversity among contemporaneous magmatic systems could possibly contribute to some of the diversity observed across Carlin-type Au districts in Nevada.

Nevada↗
USGS2024

System characterization report on the Earth Surface Mineral Dust Source Investigation (EMIT) sensor

Executive Summary This report addresses system characterization of the Earth Surface Mineral Dust Source Investigation (EMIT) sensor, an imaging spectrometer developed by the National Aeronautics and Space Administration. This report is part of a series of system characterization reports produced and delivered by the U.S. Geological Survey Earth Resources Observation and Science Cal/Val Center of Excellence. These reports present and detail the methodology and procedures for characterization; present technical and operational information about the specific sensing system being evaluated; and provide a summary of test measurements, data retention practices, data analysis results, and conclusions. The Earth Resources Observation and Science Cal/Val Center of Excellence system characterization team completed data analyses to characterize the geometric (interior and exterior) and radiometric performances. Results of these analyses indicate that the EMIT sensor has a band-to-band geometric performance in the range of −0.355 to 0.210 pixel with a few exceptions of shortwave infrared channels. Geometric offset relative to the Landsat 8 Operational Land Imager ranged from −15.966 meters (−0.266 pixel) to 43.844 meters (0.731 pixel). Offset of a radiometric comparison ranged from −0.016 to 0.025, and slope of a radiometric comparison ranged from 0.837 to 0.985. EMIT agreed with Radiometric Calibration Network measurements within 5 percent across most of the spectral channels.

Open-File Report↗
USGS2025

Factors influencing landslide occurrence in low-relief formerly glaciated landscapes: Landslide inventory and susceptibility analysis in Minnesota, USA

In landscapes recently impacted by continental glaciation, landslides may occur where topographic relief has been generated by the drainage of glacial lakes and ensuing post-glacial fluvial network development into unconsolidated glacially derived sediments and exhumed bedrock. To investigate linkages among environmental variables, post-glacial landscape development, and landslides, we created a landslide inventory of nearly 10,000 landslides in five regions of the formerly glaciated low-relief state of Minnesota, USA. Multivariate logistic regression indicates the importance of slope angle, lithology, and the development of stream valleys to landslide distribution. Areas underlain by fine-grained glaciolacustrine and nearshore deposits that are incised by streams are particularly prone to shallow (<1-2 m depth) landslides. Landslides also occur in a wide range of glacial and fluvial deposits, and as rockfall in layered Paleozoic sedimentary rocks in central and southern Minnesota and Precambrian igneous and sedimentary rocks in northeastern Minnesota. Although no more than 1-2% of the studied regions are susceptible to landslides, they can pose risk to life and safety, damage infrastructure, and impact water quality. The combination of recently generated low-relief steep slopes, extensive unconsolidated sediments, and layered sedimentary bedrock make this formerly glaciated landscape more susceptible to landslides than current national-scale models indicate.

Minnesota↗
USGS2026

Tringa flavipes (Lesser Yellowlegs) from separate breeding sites subdivides the Prairie Pothole Region in space and time during southbound migration

Some staging regions support multiple groups of the same migratory species, each of which may use the region differently. Characterizing the ways, in which separate groups use such regions can therefore help to identify vulnerabilities during this sensitive period of the annual cycle. The Prairie Pothole Region (PPR) is a massive wetland complex in the northern Great Plains of North America used by ∼11 million shorebirds during migration. The PPR has been heavily modified by agriculture and is experiencing varied effects of global climate change, threatening the health of the shorebirds that rely on it. Here, we used 6 seasons of southbound tracking data of Tringa flavipes (Lesser Yellowlegs)—a long-distance migratory shorebird species with an estimated population decline of 63% over the last 4 decades—from 9 sites across their breeding range to explore differences in migratory behavior within this important staging region. We found that 75% of tracked individuals used the region during southbound migration, and T. flavipes from different breeding sites detoured 110–875 km from their most direct migratory route to access the PPR. Individuals that arrived later stayed longer and made more stops within the region than those that arrived early. Individuals originating from different breeding sites also displayed spatial and temporal segregation within the region: T. flavipes from southwest and central Alaska relied heavily on the northwestern PPR, while those from Canada used the central and southeastern portions of the PPR. Finally, timing of use varied among groups, but the southeastern PPR became increasingly important over the course of the southbound migratory window, as other wetlands likely dried out. Our study highlights the portions of the PPR of critical importance to migrating T. flavipes and the diversity of ways, in which different groups from within the same species can use a single staging region.

Alaska, Manitoba, Northwest Territories, Ontario, ↗
USGS2025

Approximate inland extent of saltwater intrusion at the base of the Biscayne aquifer, Miami-Dade County, Florida, 2022

Miami-Dade County is part of a densely populated urban corridor in southeastern Florida. The Biscayne aquifer serves as Miami-Dade County’s primary drinking water source and is characterized by highly permeable karstic limestone and carbonate sand. The aquifer’s coastal location and permeable nature make it susceptible to saltwater intrusion. Monitoring the current inland extent and the rate of movement of the saltwater front in the aquifer can inform management strategies for conserving the long-term sustainability of the county’s water supply. In the 1950s, the U.S. Geological Survey published a map of the inland extent of saltwater intrusion in the Biscayne aquifer and has continued to update this map to monitor changes over time, with the most recent update published in 2018. An updated map has been created showing the approximate inland extent of saltwater intrusion in the Biscayne aquifer in eastern Miami-Dade County in 2022, with the 2018 extent shown for comparison. The inland extent of saltwater intrusion was mapped through the interpretation of borehole electromagnetic induction logs and measurements of chloride and specific conductance in groundwater samples. The location of the saltwater interface at the base of the Biscayne aquifer was represented by the 1,000-milligram-per-liter isochlor. This report describes changes in the location of the saltwater interface from 2018 to 2022. By 2022, the saltwater interface had moved farther inland in both the northern and southern parts of the county, advancing by as much as 0.3 kilometer in the north and up to 0.8 kilometer in the Model Land Area to the south. However, it remained relatively unchanged from its 2018 position in the east-central part of the county.

Florida↗
USGS2025

The 3D National Topography Model Call for Action—Part 2: The Next Generation 3D Elevation Program

The three-dimensional (3D) National Topography Model initiative to integrate elevation and hydrography data includes the next generation of hydrography data from the 3D Hydrography Program and the next generation of elevation data from the 3D Elevation Program (3DEP). The first-ever collection of light detection and ranging (lidar) data for the nation (IfSAR for Alaska) provides a critical baseline reference, and the addition of multiple repeat elevation mapping projects as part of the next generation of 3DEP would substantially expand analysis capabilities. As the U.S. Geological Survey (USGS) is closing in on our goal of complete coverage with 3DEP data available or in progress for 98.3 percent of the Nation at the end of fiscal year 2024, the USGS is already transitioning to the next generation of 3DEP. Based on the 3D Nation Study results and input from a broad range of stakeholders, the USGS National Geospatial Program has finalized a new design for 3DEP that provides increased lidar quality levels and refresh rates. The new program is designed with more flexibility to meet changing user needs and take advantage of improvements in mapping technologies. The program will aim to expand the level of interagency coordination for topobathymetric lidar acquisition for inland rivers. The next generation of 3DEP will also aim to emphasize research, including advancing program design, products, and services and engaging and leveraging the evolving 3D industry. Research goals also include becoming more flexible in meeting user needs and taking advantage of evolving remote-sensing technologies. The program also plans to move from focusing on producing standard products to producing a concept of a 3D Nation Ecosystem with a variety of inputs, products, and services.

Circular↗
USGS2025

Landsliding follows signatures of wildfire history and vegetative regrowth in a steep coastal shrubland

Five years after the deadly and destructive 9 January 2018 Montecito debris flows (Santa Barbara County, California, USA), an atmospheric river storm on 9 January 2023 triggered widespread landsliding that affected many of the same drainages in the Santa Ynez Mountains. Using high-resolution aerial imagery, we identified >10,000 landslides over an ∼160 km 2 area. Most of the landslides were shallow (<1 m in depth) translational debris slides that initiated on steep (∼40°), south-facing hillslopes, with the highest incidence of landsliding in a sandstone-dominated bedrock unit. The landslides mobilized into debris flows and delivered substantial quantities of sediment downstream, which contributed to costly infrastructure impairments. We detected order-of-magnitude differences in landslide density across the study area that could not be attributed to variations in geomorphology (topographic aspect and slope), geology (bedrock type), or hydrology (seasonal antecedent rainfall, peak hourly storm rainfall intensity, total storm rainfall), which are usually considered relevant factors for shallow landsliding. Rather, we found that vegetation regrowth following wildfire was likely a relevant factor associated with the highly variable landslide densities. Hillslopes with less and different types of vegetation regrowth after fire appear to have been more susceptible to shallow landslides. We identify a possible vegetation control on postfire landsliding, which highlights an opportunity for hypothesis testing using more advanced techniques to track the evolution of vegetation cover and vegetation type in steep shrubland environments following wildfire.

California↗
USGS1986

Water-quality appraisal of NASQAN stations below impoundments, eastern Tennessee

The National Stream Quality Accounting Network (NASQAN) is a network of stations at which systematic and continuing water-quality data are collected. Major objectives of this U.S. Geological Survey program are (1) to depict areal variability of streamflow and water-quality conditions nationwide on a year-by-year basis and (2) to detect long-term changes in streamflow and stream quality. Several NASQAN stations in East Tennessee are downstream from impoundments which have a significant effect on water quality. NASQAN data obtained from the Tennessee River below Watts Bar Dam and the Clinch River below Melton Hill Dam were compared to water-quality data from the basins upstream. The comparison indicates that NASQAN data obtained below impoundment may not be adequate to describe a composite picture of water quality in the accounting unit. Detention time of storage in the impoundments is believed to moderate the range of constituent values observed at the NASQAN stations. Data obtained upstream and downstream from Watts Bar Dam indicate that the water sampled at the NASQAN station comes from stratified layers of the impoundment and is not representative of an integrated sample of water from the impoundment. Values of total recoverable iron suggest that, because of adsorption to sediments in impoundments, some constituents are not accurately described by sampling below impoundments. Relations between water-quality constituents and flow at stations on the Clinch River and Tennessee River are not well defined due to regulation. Direct load computations for many constituents were therefore not possible, which diminished the utility of data from these NASQAN stations to account for quantity versus quality of the water. Load computations were only possible for ionic constituents through use of a continuous specific-conductance record as an intermediary. Compensation for the effects of discharge prior to application of the Seasonal Kendall test for trends could not be done and identification of trends in water-quality constituents caused by some process (source) change was not possible. Some water-quality trends indicated by data from the Clinch and Tennessee Rivers might reflect the decreasing trend in discharge during the 1972-82 water years. Thus the stations below Watts Bar Dam and below Melton Hill Dam do not adequately meet the NASQAN objective to detect and assess long-term changes in stream quality.

Tennessee↗
USGS2025

Natural source zone depletion of crude oil in the subsurface: Processes controlling mass losses of individual compounds

At many petroleum hydrocarbon spill sites, residual spilled product forms a long-term source of groundwater contamination. The phrase source zone natural depletion is used to refer to the mass loss rates. Overall mass lost under environmental conditions was analyzed using conservative biomarker concentrations for a 1979 oil spill in northern Minnesota, USA. After 40–41 years, an average of 50% of the mass was lost with values ranging from 22% to 57% depending on location. It is also important to understand the composition changes in the source. To understand controls on the losses of individual compounds, concentrations of volatile hydrocarbons in oil samples were compared with aqueous solubilities, and pore-space oil saturations. The results of the comparison show that losses of the oil compounds were controlled by pore-space oil saturations, solubility, and susceptibility to degradation under methanogenic conditions. Compounds that degrade under methanogenic conditions, including toluene, o -xylene, and n -alkanes are more depleted compared to benzene, ethylbenzene, and m - and p -xylene for which losses are dominated by dissolution. These rates and compound-specific behaviors form a foundation for improved modeling approaches and risk analyses.

Minnesota↗
USGS2026

Core microbiomes as a potential fingerprinting method of Western USA dust sources

Introduction: Changing frequency and intensity of dust emissions impacts ecosystems and human health. Dust carries microbes, nutrients, heavy metals, and other materials that may change environmental biogeochemistry at deposition sites. Identifying dust sources provides key information on where and when mitigation strategies should be employed. However, commonly used geochemical or isotopic tracers are often not capable of distinguishing between geographic regions. Methods: We explored whether soil bacterial communities may provide distinct fingerprints of dust sources in the western United States. We identified bacterial core communities of dust from ten locations monitored by the National Wind Erosion Research Network (NWERN) with varied land use (cropland, rangeland, and playa), and compared communities to location, soil, and regional characteristics. Samples were collected monthly from Modified Wilson and Cooke (MWAC) samplers, composited by season (spring, summer, and fall), and analyzed using 16S rRNA sequencing. Results: We found distinct bacterial core communities that reflected dust source characteristics. In order of importance, precipitation levels ( p = 0.0001), location ( p = 0.0001), soil texture ( p = 0.0001), seasonality ( p = 0.0001), and elevation (p = 0.0002) were correlated with bacterial community composition. Discussion: Distinct bacterial core communities were associated with site characteristics such as biocrusts, playas, and military base proximity. Our results suggest that the use of core microbiomes may offer a fingerprinting method to identify dust source regions.

Colorado, Nevada, New Mexico, North Dakota, Oklaho↗
USGS2025

The 1912 Ms 7.2 earthquake in the Denali region of central Alaska

The 2002 M w 7.9 earthquake in central Alaska ruptured 340 km on three faults—Susitna Glacier thrust fault, Denali fault, Totschunda fault—crossing both the Richardson Highway and the Alaska Pipeline. Its occurrence prompted renewed interest in historical large earthquakes that possibly originated on the Denali fault. One of these earthquakes was a M s 7.2 event on July 7, 1912, which we revisit with two approaches: (1) probabilistic relocation of the epicenter using globally recorded arrival times, and (2) compilation and reassessment of shaking intensity reports to estimate a macroseismic epicenter. Our preferred instrumental epicenter is west of the Parks Highway and in agreement with the maximum‐reported shaking, which was from the Parker–Browne expedition of Denali. We also relocated a M s 6.4 aftershock, whose epicenter is 11 km from the mainshock. Candidate faults for the 1912 earthquake include the Denali fault, the McLeod Creek thrust fault, and the Kantishna Hills thrust fault. Future analysis of active faults, paleoseismic results, 1912 instrumental data, and 1912 felt reports may help in interpreting the fault and mechanism of the 1912 earthquake.

Alaska↗
USGS2023

Explosive trachyte eruptions from the Al Efairia volcanic center in northern Harrat Rahat, Kingdom of Saudi Arabia

Harrat Rahat is an alkali basalt, continental, intraplate volcanic field located within the central-western part of the Kingdom of Saudi Arabia. The northern quarter of Harrat Rahat contains evolved volcanic products that achieve trachyte compositions (>60 weight percent SiO 2 ). Within the Al Efairia volcanic center, pyroclastic-flow and -surge deposits that reflect explosive trachyte volcanism (and minor exposed lava domes that reflect effusive trachyte eruptions) sit at the surface as the youngest expression of volcanic activity within this part of the Harrat Rahat volcanic field. Five trachyte deposits emplaced explosively have been identified within the Al Efairia volcanic center based on geologic mapping, petrography, geochemistry, and paleomagnetism. These units are the trachytes of Um Rgaibah, Gura 5, Gura 4, Al Efairia, and Al Qayf, in descending stratigraphic order. Here, we present 14 40 Ar/ 39 Ar analyses from four of these units, which yield eruption ages of 4.2±5.2 thousand years (ka) for the trachyte of Um Rgaibah, 79.7±1.6 ka for the trachyte of Gura 5, 84.3±1.6 ka for the trachyte of Gura 4, and 88.0±1.8 ka for the trachyte of Al Efairia. The eruption age of the trachyte of Al Qayf has been constrained to between 410.3±3.4 and 418.8±1.9 ka using paleomagnetic correlations and 40 Ar/ 39 Ar ages from overlying and underlying intermediate composition lava flows. Most of these trachytes have distinct geochemical compositions, petrographic characteristics, and directions of remanent magnetization. The exceptions are for the trachytes of Gura 4 and Gura 5, which overlap in their geochemical, petrographic, paleomagnetic, and geochronologic affinities. Based on these similarities, we interpret the trachytes of Gura 4 and Gura 5 to have erupted during a closely spaced (a few decades) time interval from the same magma batch but from craters that are >2 kilometers (km) apart. The eruption of the trachyte of Al Efairia at 88.0±1.8 ka is the result of a different magma batch that erupted a few thousand years prior to the trachytes of Gura 4 and Gura 5. The Al Efairia volcanic center is remarkably different from the Matan volcanic center located ~10 km to the north, which has also erupted young (<150 ka) trachytes. The Matan volcanic center has been shown to produce trachyte compositions only after eruption of basalt followed by intermediate lava flows, whereas only trachyte compositions have erupted within the Al Efairia volcanic center over this same time interval.

Al Efairia volcanic center, Harrat Rahat↗