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Geology topics

Research about Virginia

Source-linked reports with geographic coverage including Virginia.

At least 379 records · Page 21Linked to original sources
USGS1999

Geologic map of the Middletown quadrangle, Frederick, Shenandoah, and Warren Counties, Virginia

The Middletown 1:24,000-scale quadrangle is one of several quadrangles in Frederick County, Virginia mapped or being mapped by geologists from the U.S. Geological Survey in Reston, VA with funding from the National Cooperative Geologic Mapping Program. This map was originally published as a paper product in 1999. It has been converted to GIS-based digital form. This work is part of a project being lead by the U.S. Geological Survey Water Resources Discipline, Virginia District, to investigate the geologic framework and groundwater resources of Frederick County as well as other areas in the northern Shenandoah Valley of Virginia and West Virginia. For more information about the Project see: http://geology.er.usgs.gov/eespteam/Karst/index.html for Geologic Discipline efforts and http://va.water.usgs.gov/va134/index.htm for Water Resources Discipline efforts.

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USGS1999

Measuring streamflow in Virginia (1999 revision)

The U.S. Geological Survey (USGS), U.S. Department of the Interior, is the Nation's largest Earth-science information agency. Among its many responsibilities, such as map making and providing information on earthquakes and other natural hazards, the USGS provides information on the Nation's water resources. The USGS has collected and analyzed hydrologic (water-related) information for more than 100 years. In 1889, the first streamflow-gaging station (a site where regular observations of streamflow data are collected) operated in the United States by the USGS was established on the Rio Grande near Embudo, New Mexico. As the need for streamflow data increased, the USGS's streamflow-gaging program has grown to include more than 7,000 continuous-record streamflow-gaging stations. More than 90 percent of these stations are operated with at least partial support from State, local, and other Federal agencies. In Virginia, the Department of Environmental Quality (DEQ) is a major cooperator in the streamflow-gaging program, which consists of 152 continuous-record streamflow-gaging stations located throughout the State (fig. 1). The USGS and DEQ cooperate to publish the annual USGS State data report, "Water Resources Data-Virginia;" this two-volume publication includes streamflow data collected at the 152 streamflow-gaging stations, chemical data collected at more than 24 streamflow-gaging stations, and ground-water data collected from more than 338 wells.

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USGS1999

The effects of the Chesapeake Bay impact crater on the geological framework and correlation of hydrogeologic units of the lower York-James Peninsula, Virginia

This report documents the highly variable structure, stratigraphy, and buried topography of the outer rim of the Chesapeake Bay impact crater created by its impact and burial. Lithologies of cores are correlated with borehole geophysical logs to characterize the physical properties of the stratigraphic units and their geophysical signatures. The correlation between cores, well cuttings, and borehole geophysical logs is augmented with seismic-reflection data, and these data are compiled into a lithostratigraphic cross section that illustrates the geological framework of the lower York-James Peninsula and immediate surrounding areas.

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USGS1999

The potential for saltwater intrusion in the Potomac aquifers of the York-James Peninsula, Virginia

The most productive aquifers of the Virginia Coastal Plain are in the Potomac Formation. Water supplies in the Potomac aquifers are impaired, however, by saltwater in some areas. A two-dimensional, densitydependent, solute-transport model was used to investigate saltwater movement in the Potomac aquifers and the potential for saltwater intrusion or upward migration of saltwater. The model was designed to represent a simplified section of the Potomac aquifers and associated confining units near Lee Hall, Va. Solute-transport simulations show that the direction of ground-water flow and the hydrogeologic properties, particularly the permeability of aquifers and the distribution of confining sediments in the Potomac Formation, control the system hydrodynamics and saltwater movement in the Potomac aquifers. The simulations indicate lateral intrusion for the Lower Potomac aquifer near Lee Hall, Va. Velocity vectors of the simulations indicate that a hypothetical, but typical, production well in the Middle Potomac aquifer could induce upconing only within the immediate vicinity of the well. Migration of saltwater from the Middle and Lower Potomac aquifers east of the hypothetical well also was indicated by the simulations.

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USGS1999

Assessment of landscape correlates of Eastern hemlock decline due to hemlock woolly adelgid

Eastern hemlock ( Tsuga canadensis ) is in decline throughout its range in the eastern US due to infestation by an exotic insect pest, the hemlock woolly adelgid ( Adelges tsugae ). In Shenandoah National Park, the hemlock woolly adelgid (HWA) rapidly killed many stands of hemlock after first appearing in the late-1980’s, while having only minor impact in other stands. At present, few investigators have examined the mechanisms that produce this discontinuous impact, although landscape factors are predicted to play a major role (Orwig and Foster, 1998: Perry 1988). In an effort to address possible landscape correlates to hemlock decline, we conducted a preliminary analysis of 5 years of hemlock health estimates in comparison to measures of terrain, stand isolation, and potential dispersal corridors at the stand level. We found that elevation, slope, light conditions, and distance to streams all exhibited relatively strong correlation with hemlock decline, although the relationship varied by year. In addition, there appears to be some evidence of spatial autocorrelation in decline, suggesting that similar environmental conditions are either controlling the adelgid or making hemlock stands more susceptible to HWA. We are using the results of this preliminary analysis to guide more detailed efforts aimed at modeling hemlock stand vulnerability as a result of site, landscape, and regional factors.

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USGS1998

Diets of nestling gull-billed terns in coastal Virginia

We studied the diets of nestling Gull-billed Terns (Sterna nilotica) at colonies in coastal Virginia during the breeding seasons of 1995 and 1996 as part of a long-term study of the species. No previous quantitative assessments had been made of diets of this species anywhere along the Atlantic Coast, and only a few observations had been reported from other coastal areas in the southern United States. During 80 h of observations over the two seasons, 757 feeding observations were made, primarily at two colony sites. We examined how prey type (fish, marine invertebrates, terrestrial prey) and size were influenced by year, tide cycle, season (early and late) and age of the young (small chicks < 7 d old versus large chicks > 7 d). We did not find significant year differences, but all other factors revealed statistically significant results. Older (>7 d) chicks were fed relatively more terrestrial and marine invertebrate prey than were younger chicks. In June (early season), fewer fish and terrestrial prey were fed to chicks than later (July-August). Most prey were less than one bill length in size, with the majority of the smallest prey being marine invertebrates. Tide cycle influenced prey delivered with terrestrial prey becoming relatively more important during high and ebb periods than during low and flood tides when aquatic prey dominated. The major marine invertebrate prey taken was the fiddler crab (Uca spp.). Terrestrial prey consisted mostly of large odonates and orthopterans. Unlike earlier reports from Europe, we found no regurgitated food pellets in any of the colonies in either year. This study confirms that the Gull-billed Tern is an extremely opportunistic feeder and has adapted to a variety of habitats, helping to explain its cosmopolitan distribution.

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USGS1998

Glimpses of the Ice Age from I-81: Lee Ranger District

Travelers on Interstate Highway 81 can see remnants of the Ice Age on the mountains between Strasburg and Harrisonburg, Virginia. Scattered along the miles of green, forested mountains are many gray patches without any forests. These treeless patches, or openings, in the steep mountain forests are block fields - geologic features that owe their origin to the Ice Age.

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USGS1998

Surficial geology of Shaver Hollow, Shenandoah National Park

At the request of Shenandoah National Park and the Department of Environmental Sciences at the University of Virginia, the US Geological Survey has completed an examination and map of the surficial deposits in Shaver Hollow. The work was carried out as part of the US Geological Survey - National Park Service cooperative agreement implemented in 1994. Shaver Hollow is a small, well defined drainage basin on the west slope of the Blue Ridge about 6.5 miles south of Thornton Gap and can be reached by trail from mile 37.9 on the Skyline Drive. The hollow is drained by the North Fork of Dry Run, and the watershed within the Shenandoah National park is only 2 square miles in area. The area has been the site of extensive investigations by faculty and students at the University of Virginia and by NPS scientists and investigators studying the interaction of atmosphere chemistry, water composition, and the biota of the hollow (Furman and others, written communication, 1997). Modeling of the chemistry of Dry Run surface water, based on atmospheric, biologic, and geologic data, has been attempted with limited success. Better understanding of the surficial deposits and the interaction of streams and springs with near surface materials is needed before more sophisticated models can be devised. Although the bedrock lithology was mapped at a small scale (1:62,000-scale; Gathright, 1976) no examination of the surficial deposits of the hollow was made. The description of deposits contained herein is based on field observations carried out in September - November, 1996. Also included with this report is a 1/12,000-scale map of the surficial geology of Shaver Hollow (figure 1).

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