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

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At least 217 records · Page 12Linked to original sources
USGS2020

Mapping metabolic activity at single cell resolution in intact volcanic fumarole soil

Interactions among microorganisms and their mineralogical substrates govern the structure, function, and emergent properties of microbial communities. These interactions are predicated on spatial relationships, which dictate metabolite exchange and access to key substrates. To quantitatively assess links between spatial relationships and metabolic activity, this study presents a novel approach to map all organisms, the metabolically active subset, and associated mineral grains, all while maintaining spatial integrity of an environmental microbiome. We applied this method at an outgassing fumarole of Vanuatu’s Marum Crater, one of the largest point sources of several environmentally relevant gaseous compounds, including H2O, CO2, and SO2. With increasing distance from the soil-air surface and from mineral grain outer boundaries, organism abundance decreased but the proportion of metabolically active organisms often increased. These protected niches may provide more stable conditions that promote consistent metabolic activity of a streamlined community. Conversely, mineral exteriors accumulate more organisms that may cover a wider range of preferred conditions, implying that only a subset of the community will be active under any particular environmental regime. More broadly, the approach presented here allows investigators to see microbial communities “as they really are” and explore determinants of metabolic activity across a range of microbiomes.

FEMS Microbiology Letters↗
USGS2000

Development of a grid-cell topographic surface for Okefenokee Swamp, Georgia

The Okefenokee Swamp is a 160,000 ha freshwater wetland in Southeast Georgia, USA that developed in a landscape basin. Hydrologic variability across the swamp suggests that water-surface elevations are not uniform across the swamp. The topographic surface map discussed herein was developed to describe the swamp topography at local to landscape scales and relate the swamp peat- and sand-surface elevations to elevation above mean sea level. These data were then used to relate water-surface elevations across the swamp so that the swamp hydrologic environment could be described spatially and temporally with a spatial hydrology model. The swamp was divided into 5 sub-basins that reflect similar seasonal hydrodynamics but also indicate local conditions unique to the basins. Topographic gradient influences water-level dynamics in the western swamp (2 sub-basins), which is dominated by the Suwannee River floodplain. The eastern swamp (3 sub-basins) is terraced, and the regional hydrology is driven less by topographic gradient and more by precipitation and evapotranspiration volumes. The relatively steep gradient and berm and lake features in the western swamp's Suwannee River floodplain limit the spatial extent of the Suwannee River sill's effects, whereas system sensitivities to evapotranspiration rates are more important drivers of hydrology in the eastern swamp.

Georgia↗
USGS2003

MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- Three additions to the Hydrogeologic-Unit Flow (HUF) Package: Alternative storage for the uppermost active cells, Flows in hydrogeologic units, and the Hydraulic-conductivity depth-dependence (KDEP) capability

The Hydrogeologic-Unit Flow (HUF) Package is an internal flow package for MODFLOW-2000 that allows the vertical geometry of the system hydrogeology to be defined differently than the definition of model layers. Effective hydraulic properties for the model layers are calculated using the hydraulic properties of the hydrogeologic units. The HUF Package can be used instead of the Block-Centered Flow (BCF) or the Layer Property Flow (LPF) Packages. This report documents three additions to the HUF Package.

Open-File Report↗
USGS2007

Geomorphology and tectonics at the intersection of Silurian and Death Valleys, Southern California - 2005 Guidebook Pacific Cell Friends of the Pleistocene

This publication describes results from new regional and detailed surficial geologic mapping, combined with geomorphologic, geochronologic, and tectonic studies, in Silurian Valley and Death Valley, California. The studies address a long-standing problem, the tectonic and geomorphic evolution of the intersection between three regional tectonic provinces: the eastern California shear zone, the Basin and Range region of southern Nevada and adjacent California, and the eastern Mojave Desert region. The chapters represent work presented on the 2005 Friends of the Pleistocene field trip and meeting as well as the field trip road log.

California↗
USGS2008

Preliminary Toxicological Analysis of the Effect of Coal Slurry Impoundment Water on Human Liver Cells

Coal is usually 'washed' with water and a variety of chemicals to reduce its content of sulfur and mineral matter. The 'washings' or 'coal slurry' derived from this process is a viscous black liquid containing fine particles of coal, mineral matter, and other dissolved and particulate substances. Coal slurry may be stored in impoundments or in abandoned underground mines. Human health and environmental effects potentially resulting from leakage of chemical substances from coal slurry into drinking water supplies or aquatic ecosystems have not been systematically examined. Impoundments are semipermeable, presenting the possibility that inorganic and organic substances, some of which may be toxic, may contaminate ground or surface water. The Agency for Toxic Substances and Disease Registry, part of the Centers for Disease Control and Prevention, has concluded that well water in Mingo County, West Virginia, constitutes a public health hazard.

Open-File Report↗
USGS2020

Observations of coastal change and numerical modeling of sediment-transport pathways at the mouth of the Columbia River and its adjacent littoral cell

Bathymetric and topographic surveys performed annually along the coastlines of northern Oregon and southwestern Washington documented changes in beach and nearshore morphology between 2014 and 2019. Volume change analysis revealed measurable localized erosion and deposition throughout the study area, but significant net erosion at the regional scale (several kilometers [km]) was limited to Benson Beach, Wash., a 3-km-long stretch of coastline immediately north of the Columbia River inlet. Despite the placement of approximately 6.3 million cubic meters (Mm 3 ) of sand dredged from the Columbia River navigational channel at nearshore placement sites located nearby, Benson Beach eroded 2.1±0.8 Mm 3 over the 5-year (yr) monitoring time period (420,000 cubic meters/year [m 3 /yr]). A hydrodynamic and sediment transport model was applied to simulate sediment transport fluxes, and a new visualization technique was developed to evaluate the linkages between nearshore dredge placement sites and adjacent coastlines near the mouth of the Columbia River. The model results indicate the dominance of wave processes on sediment-transport patterns outside of the inlet and suggest that the current configuration of the nearshore dredge placement sites can be improved to more efficiently enhance the sediment budget of Benson Beach to reduce erosion and mitigate associated coastal change hazards.

Oregon, Washinton↗