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At least 451 records · Page 25Linked to original sources
USGS2007

Scoping of Flood Hazard Mapping Needs for Lincoln County, Maine

Background The Federal Emergency Management Agency (FEMA) developed a plan in 1997 to modernize the FEMA flood mapping program. FEMA flood maps delineate flood hazard areas in support of the National Flood Insurance Program (NFIP). FEMA's plan outlined the steps necessary to update FEMA's flood maps for the nation to a seamless digital format and streamline FEMA's operations in raising public awareness of the importance of the maps and responding to requests to revise them. The modernization of flood maps involves conversion of existing information to digital format and integration of improved flood hazard data as needed. To determine flood mapping modernization needs, FEMA has established specific scoping activities to be done on a county-by-county basis for identifying and prioritizing requisite flood-mapping activities for map modernization. The U.S. Geological Survey (USGS), in cooperation with FEMA and the Maine Floodplain Management Program (MFMP) State Planning Office, began scoping work in 2006 for Lincoln County. Scoping activities included assembling existing data and map needs information for communities in Lincoln County, documentation of data, contacts, community meetings, and prioritized mapping needs in a final scoping report (this document), and updating the Mapping Needs Update Support System (MNUSS) database with information gathered during the scoping process. The average age of the FEMA floodplain maps in Lincoln County, Maine is at least 17 years. Many of these studies were published in the mid- to late-1980s, and some towns have partial maps that are more recent than their study. However, in the ensuing 15-20 years, development has occurred in many of the watersheds, and the characteristics of the watersheds have changed with time. Therefore, many of the older studies may not depict current conditions nor accurately estimate risk in terms of flood heights or flood mapping.

Open-File Report↗
USGS2006

Sedimentation and Occurrence and Trends of Selected Chemical Constituents in Bottom Sediment, Empire Lake, Cherokee County, Kansas, 1905-2005

For about 100 years (1850-1950), the Tri-State Mining District in parts of southeast Kansas, southwest Missouri, and northeast Oklahoma was one of the primary sources of lead and zinc ore in the world. The mining activity in the Tri-State District has resulted in substantial historical and ongoing input of cadmium, lead, and zinc to the environment including Empire Lake in Cherokee County, southeast Kansas. The environmental contamination caused by the decades of mining activity resulted in southeast Cherokee County being listed on the U.S. Environmental Protection Agency's National Priority List as a superfund hazardous waste site in 1983. To provide some of the information needed to support efforts to restore the ecological health of Empire Lake, a 2-year study was begun by the U.S. Geological Survey in cooperation with the U.S. Fish and Wildlife Service and the Kansas Department of Health and Environment. A combination of sediment-thickness mapping and bottom-sediment coring was used to investigate sediment deposition and the occurrence of cadmium, lead, zinc, and other selected constituents in the bottom sediment of Empire Lake. The total estimated volume and mass of bottom sediment in Empire Lake were 44 million cubic feet and 2,400 million pounds, respectively. Most of the bottom sediment was located in the main body and the Shoal Creek arm of the reservoir. Minimal sedimentation was evident in the Spring River arm of the reservoir. The total mass of cadmium, lead, and zinc in the bottom sediment of Empire Lake was estimated to be 78,000 pounds, 650,000 pounds, and 12 million pounds, respectively. In the bottom sediment of Empire Lake, cadmium concentrations ranged from 7.3 to 76 mg/kg (milligrams per kilogram) with an overall median concentration of 29 mg/kg. Compared to an estimated background concentration of 0.4 mg/kg, the historical mining activity increased the median cadmium concentration by about 7,200 percent. Lead concentrations ranged from 100 to 950 mg/kg with an overall median concentration of 270 mg/kg. Compared to an estimated background concentration of 33 mg/kg, the median lead concentration was increased by about 720 percent as a result of mining activities. The range in zinc concentrations was 1,300 to 13,000 mg/kg with an overall median concentration of 4,900 mg/kg. Compared to an estimated background concentration of 92 mg/kg, the median zinc concentration was increased by about 5,200 percent. Within Empire Lake, the largest sediment concentrations of cadmium, lead, and zinc were measured in the main body of the reservoir. Within the Spring River arm of the reservoir, increased concentrations in the downstream direction likely were the result of tributary inflow from Short Creek, which drains an area that has been substantially affected by historical lead and zinc mining. Compared to nonenforceable sediment-quality guidelines, all Empire Lake sediment samples (representing 21 coring sites) had cadmium concentrations that exceeded the probable-effects guideline (4.98 mg/kg), which represents the concentration above which toxic biological effects usually or frequently occur. With one exception, cadmium concentrations exceeded the probable-effects guideline by about 180 to about 1,400 percent. With one exception, all sediment samples had lead concentrations that exceeded the probable-effects guideline (128 mg/kg) by about 10 to about 640 percent. All sediment samples had zinc concentrations that exceeded the probable-effects guideline (459 mg/kg) by about 180 to about 2,700 percent. Overall, cadmium, lead, and zinc concentrations in the bottom sediment of Empire Lake have decreased over time following the end of lead and zinc mining in the area. However, the concentrations in the most recently deposited bottom sediment (determined for 4 of 21 coring sites) still exceeded the probable-effects guideline by about 440 to 640 percent for cadmium, about 40 to 80 percent for lead, and about 580

Scientific Investigations Report↗
USGS1984

Design of a ground-water-quality monitoring network for the Salinas River basin, California

A regional ground-water quality monitoring network for the entire Salinas River drainage basin was designed to meet the needs of the California State Water Resources Control Board. The project included phase 1--identifying monitoring networks that exist in the region; phase 2--collecting information about the wells in each network; and phase 3--studying the factors--such as geology, land use, hydrology, and geohydrology--that influence the ground-water quality, and designing a regional network. This report is the major product of phase 3. Based on the authors ' understanding of the ground-water-quality monitoring system and input from local offices, an ideal network was designed. The proposed network includes 317 wells and 8 stream-gaging stations. Because limited funds are available to implement the monitoring network, the proposed network is designed to correspond to the ideal network insofar as practicable, and is composed mainly of 214 wells that are already being monitored by a local agency. In areas where network wells are not available, arrangements will be made to add wells to local networks. The data collected by this network will be used to assess the ground-water quality of the entire Salinas River drainage basin. After 2 years of data are collected, the network will be evaluated to test whether it is meeting the network objectives. Subsequent network evaluations will be done very 5 years. (USGS)

Water-Resources Investigations Report↗
USGS1985

Distribution and transport of trace substances in the Schuylkill River basin from Berne to Philadelphia, Pennsylvania

During the period from October 1978 to March 1981, the U.S. Geological Survey assessed the river quality of the Schuylkill River basin in Pennsylvania from the headwaters to the Fairmount Dam at Philadelphia (river mile 8.4). The assessment focused on the distribution and transport of trace metals and organic substances (trace substances). Trace metals included were arsenic, beryllium, cadmium, copper, lead, mercury, nickel, and zinc; trace organic substances included organochlorine insecticides and polychlorinated biphenyls. In general, concentrations of trace substances in the streambed sediments were greater in the main stem of the Schuylkill River than in its tributaries and exceeded the background concentrations in the study area. Concentrations of most trace metals in the sediments were lowest in the Berne area (river mile 95) and highest in the urban-industrial area of Reading (river mile 76). Concentrations generally decreased from Reading downstream to Philadelphia (river mile 10.2). Concentrations of the organochlorine insecticides chlordane, DDT and its metabolites, and dieldrin generally increased gradually from Berne to Philadelphia. Average concentrations of trace metals in the main stem of the Schuylkill River in the sediment-sized fraction, less than 0.063 millimeters, were: zinc, 603 ?g/g (micrograms per gram); lead, 284 ?g/g; copper, 252 ?g/g; nickel, 119 ?g/g; chromium, 96 ?g/g; beryllium, 8.2 ?g/g; arsenic, 0.64 ?g/g; and mercury, 0.002 ?g/g. Average concentrations of trace organic substances in sediments of the main stem of the river were: polychlorinated biphenyls, 152 ?g/kg (micrograms per kilogram); chlordane, 24 ?g/kg; DDT and its metabolites, 18 ?g/kg; and dieldrin, 1.8 ?g/kg. The average annual transport of trace substances by the river was computed for chromium, copper, lead, nickel, and zinc. Concentrations of other trace substances in the sediment-water mixtures were generally undetectable. Of the trace metals, average annual transport of zinc was the greatest, and that of nickel was the least. Transport of trace metals in the river is closely associated with and related to suspended-sediment transport. About 71 percent of the average annual total metal transport is particulate material. Yields, in tons per square mile per year, of copper, lead, zinc, and total organic carbon in the Schuylkill River basin were compared with yields in the Chattahoochee River basin (Georgia). The comparison indicates that yields, by constituent, were of the same order of magnitude. Both basins lie in the Piedmont province, and both have about the same percentage of urban land use. The frequency of occurrence of concentrations of copper, lead, and zinc in the sediment-water mixture at Manayunk in Philadelphia were compared with domestic water-supply criteria of the U.S. Environmental Protection Agency. The criteria are exceeded less than 1 percent of the time, or about 4 days per year.

Schuylkill River basin↗
USGS2007

Hydrogeologic Framework and Ground-Water Budget of the Spokane Valley-Rathdrum Prairie Aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho

The U.S. Geological Survey, in cooperation with the Idaho Department of Water Resources and Washington State Department of Ecology, investigated the hydrogeologic framework and ground-water budget of the Spokane Valley-Rathdrum Prairie (SVRP) aquifer located in northern Idaho and northeastern Washington. Descriptions of the hydrogeologic framework, water-budget components, and further data needs are provided. The SVRP aquifer, which covers about 370 square miles including the Rathdrum Prairie, Idaho, and the Spokane Valley and Hillyard Trough, Washington, is the sole source of drinking water for more than 500,000 residents. Continued growth, water-management issues, and potential effects on water availability and water quality in the aquifer and in the Spokane and Little Spokane Rivers have illustrated the need to better understand and manage the region's water resources. The SVRP aquifer consists mostly of gravels, cobbles, and boulders - deposited during a series of outburst floods resulting from repeated collapse of the ice dam that impounded ancient Glacial Lake Missoula. In most places, the SVRP aquifer is bounded by bedrock of pre-Tertiary granite or metasedimentary rocks, or Miocene basalt and associated sedimentary deposits. Discontinuous fine-grained layers are scattered throughout the SVRP aquifer at considerably different altitudes and with considerably different thicknesses. In the Hillyard Trough and the Little Spokane River Arm of the aquifer, a massive fine-grained layer with a top altitude ranging from about 1,500 to 1,700 feet and thickness ranging from about 100 to 200 feet separates the aquifer into upper and lower units. Most of the Spokane Valley part of the aquifer is devoid of fine-grained layers except near the margins of the valley and near the mouths of lakes. In the Rathdrum Prairie, multiple fine-grained layers are scattered throughout the aquifer with top altitudes ranging from about 1,700 to 2,400 feet with thicknesses ranging from 1 to more than 135 feet. The altitude of the base of the aquifer ranges from less than 1,800 feet near Lake Pend Oreille to less than 1,200 feet near the aquifer's outlet near Long Lake. The thickness of the aquifer is more than 800 feet in the northwestern part of the northern Rathdrum Prairie, through the West Channel area, and through the west-central part of the Rathdrum Prairie. In Washington, the areas of greatest thickness, more than 600 feet, are mapped in the central parts of the Spokane Valley, Spokane, and the Hillyard Trough. Recharge or inflow to the SVRP aquifer occurs from six main sources: the Spokane River, lakes, infiltration from precipitation over the aquifer, tributaries, infiltration from landscape irrigation and septic systems, and subsurface inflow. Discharge or outflow from the SVRP aquifer occurs from five main sources: the Spokane River, the Little Spokane River, pumpage, subsurface discharge to Long Lake, and infiltration of ground water to sewers. Total estimated mean annual inflow to and outflow from the SVRP aquifer is about 1,470 cubic feet per second. Several data needs were identified during this investigation that would improve the definition of the hydrogeologic framework and ground-water budget components for the SVRP aquifer study area. Deep drilling along the axis of the aquifer could determine the depth to the bottom of the aquifer where data are currently unavailable as well as identify the presence of fine-grained layers and their thickness. A more detailed analysis of the geologic and hydrologic setting near the southern ends of Spirit and Hoodoo Valleys could help determine the location of the ground-water divide between the two valleys and the Rathdrum Prairie. Better estimates of seepage into the aquifer from Coeur d'Alene Lake and Lake Pend Oreille and underflow from the aquifer to Long Lake would strengthen the recharge and discharge estimates of the aquifer. A hydrochemical study incorporating analyses of envi

Scientific Investigations Report↗
USGS1968

Depth control of some concordant intrusions

Analysis of geologic data from 54 localities, mainly in the western United States, shows that concordant igneous masses intruded zones in nearly flat-lying sedimentary rocks where the thickness of cover was 3000 to 7500 feet. The depth of intrusion was apparently affected by a well-defined parting surface (bedding plane or unconformity), static load of the overburden (lithostatic pressure), and presence of a fluid barrier above the intrusion . Most bodies intruded along well-defined bedding planes in sedimentary rocks and flow surfaces in extrusive igneous rocks; some intruded along unconformities. The range in overburden pressure is about 3000 to 7500 psi for intrusions at depths of 3000 to 7500 feet. Magma pressure for lateral injection at the lower limit of the depth range, therefore, must have exceeded 7500 psi to lift 7500 feet of overburden. A fluid barrier, such as a shale, overlies almost all intrusions studied and tended to retard upward advance of magma. At depths less than 3000 feet, the barrier shales may be brittle and easily ruptured by the fluid pressure, permitting steam and magma to escape to the surface. Below 3000 feet the shales may become ductile.

Geological Society of America Bulletin↗
USGS2019

Crustal architecture beneath the southern Midcontinent (USA) and controls on Mesoproterozoic iron-oxide mineralization from 3D geophysical models

Several types of critical mineral-bearing ore deposits in the southern Midcontinent region of the U.S. are hosted in Mesoproterozoic igneous rocks largely concealed beneath Paleozoic cover. Discerning the architecture of igneous intrusions and volcanic centers in the crust is fundamental to understanding the geologic evolution of this vast region and its mineral resources. To advance the understanding of the geologic framework beneath the Southeast Missouri Iron Metallogenic Province, we invert continental-scale magnetic and gravity anomaly data to three-dimensional (3D) physical property models. The regional models image altered and mineralized igneous rocks near the Precambrian basement surface and underlying intrusive complexes that extend down to the Moho. At shallow crustal levels, our models confirm that iron oxide-apatite ± rare earth element (IOA±REE) deposits and iron oxide-copper-gold ± cobalt (IOCG) deposits occur within or near the edges of large low density/low susceptibility early Mesoproterozoic (ca 1.4 Ga) silicic calderas and (ca 1.3 Ga) granitic plutons. Previous isotopic and geochemical studies conclude that the iron deposits and their volcanic host rocks originated from mantle-derived and crustal melts that erupted during regional extension. Extension was associated with thermal event(s) that produced the large-scale silicic magmatism related to the ca 1.45 Ga Eastern Granite Rhyolite Province (EGRP) and the 1.35 Ga Southern Granite Rhyolite Province (SGRP). We postulate that early in the evolution of the EGRP, several trans-crustal magmatic plumbing systems developed that are evident in the 3D models. The Southeast Missouri Metallogenic Province is underlain by one such magmatic system that is expressed as a northwest-trending ~ 50 km-wide by 200 km-long elongate track of high susceptibility at deep crustal levels. The high susceptibility corridor splays upward through the crust to the Precambrian surface where the iron deposits are the epigenetic manifestation of this magmatic event. Our findings confirm that the iron deposits, with no distinct connection at the surface, are connected to one large magmatic system at depth. We propose that other similar susceptibility tracks, which are present along the top of the mantle, mark additional feeder zones that allowed magma to ascend to the main eruptive centers that produced the Granite Rhyolite Provinces. The early Mesoproterozoic extensional tectonic framework established crustal-scale pathways that controlled the distribution of subsequent magmatic activity, including the ca 1.4 Ga calderas and underlying intrusions, ca 1.3 Ga silicic plutons and Phanerozoic alkaline intrusions. If these interpretations are correct, our study has identified large areas that are prospective for critical mineral-bearing ore deposits and, importantly, suggests that the Mesoproterozoic architecture may have influenced subsequent magmatism and hydrothermal activity in the southern Midcontinent of the U.S.

Ore Geology Reviews↗
USGS1991

Economic effects of western Federal land-use restrictions on U.S. coal markets

Current regulations on land use in the Western United States affect access to surface minable coal resources. This U.S. Geological Survey study analyzes the long-term effects of Federal land-use restrictions on the national cost of meeting future coal demands. The analysis covers 45 years. The U.S. Bureau of Land Management has determined the environmental, aesthetic, and economic values of western Federal coal lands and has set aside certain areas from surface coal mining to protect other valued land uses, including agricultural, environmental, and aesthetic uses. Although there are benefits to preserving natural areas and to developing areas for other land uses, these restrictions produce long-term national and regional costs that have not been estimated previously. The Dynamic Coal Allocation Model integrates coal supply (coal resource tonnage and coal quality by mining cost for 60 coal supply regions) with coal demand (in 243 regions) for the entire United States. The model makes it possible to evaluate the regional economic impacts of coal supply restrictions wherever they might occur in the national coal market. The main factors that the economic methodology considers are (1) coal mining costs, (2) coal transportation costs, (3) coal flue gas desulfurization costs, (4) coal demand, (5) regulations to control sulfur dioxide discharges, and (6) specific reductions in coal availability occurring as a result of land-use restrictions. The modeling system combines these economic factors with coal deposit quantity and quality information--which is derived from the U.S. Geological Survey's National Coal Resources Data System and the U.S. Department of Energy's Demonstrated Reserve Base--to determine a balance between supply and demand so that coal is delivered at minimum cost.

Circular↗
USGS2021

Water-quality trends of urban streams in Independence, Missouri, 2005–18

The U.S. Geological Survey and the city of Independence, Missouri, Water Pollution Control Department has studied the water quality and ecological condition of urban streams within Independence since 2005. Selected physical properties, nutrients, chloride, fecal indicator bacteria (Escherichia coli and total coliform), total dissolved solids, and suspended-sediment concentration data for base-flow and stormflow samples were used to document temporal trends in concentrations and flow-weighted concentrations; and annual loads were computed and investigated for selected nutrients, chloride, and suspended sediment. The six study sites included in this report are located on five urban streams: Rock Creek, a tributary in the city that drains to the Missouri River; three tributaries of the Little Blue River within the city (East Fork Little Blue River, Adair Creek, and Spring Branch Creek); and two sites on the main stem of the Little Blue River (one upstream from the city and one downstream from the three tributaries). Many factors such as population, land use, and climate, and combinations of these factors contributed to the significant changes in the concentrations and transport of nutrients, chloride, fecal indicator bacteria, and suspended sediment in the urban streams within Independence. The population of Independence and the amount of developed land in the urban watersheds remained unchanged during the 2005–18 study. Differences were noted in precipitation and in streamflow during the study. Annual precipitation and streamflow were separated into two time periods within the study—period 1 (2006–10), having greater annual streamflow and precipitation, and period 2 (2011–18), having about 30 percent lower annual streamflow and less precipitation. Streamflow was an important factor in the transport of nitrogen, phosphorus, chloride, and suspended sediment from the urban watersheds. Changes in data collection methodology during the study period and improvements to the city stormwater and wastewater infrastructure also could have contributed to some of the trends. Between 2009 and 2015, more than 35 million dollars of improvements were made to stormwater and wastewater infrastructure within the city. These improvements, such as additional sewage overflow holding tanks, removal of septic tanks, and improved and expanded sanitary sewer lines and storm overflows, also could have affected the decreased nutrients and fecal indicator bacteria trends among the urban streams in the study area. Models were used for analyzing streamflow-related variability in constituent concentrations and loads to determine if the water quality changed significantly during the study period. Trends in concentration data at four sites were analyzed using a statistical package called R–QWTREND and trends in load data were analyzed at six sites using a statistical package called Weighted Regressions on Time, Discharge, and Season-Kalman filter (WRTDS–K); both developed by the U.S. Geological Survey and publicly available for use. Statistically significant trends in flow-weighted nutrient concentrations and loads generally were downward during the study period. The only nutrient compound with a statistically significant upward trend in flow-weighted concentration was dissolved orthophosphate as phosphorus at the Rock Creek site and the upstream site on the Little Blue River. A statistically significant downward trend in annual dissolved ammonia load was identified at the downstream Little Blue River site. A significant upward linear trend in annual orthophosphate as phosphorus load was identified on Adair Creek. A statistically significant upward trend in dissolved chloride concentrations was identified at the downstream Little Blue River site. Road salt application near the site during the winter could have resulted in higher concentrated runoff during wet weather conditions. Annual chloride loads significantly decreased in Adair Creek and Spring Branch Creek. The mean annual chloride load transported in the drier (2011–18) period 2 was significantly less than during the wetter (2006–10) period 1, indicating that trends in precipitation runoff are an important factor in trends in annual transport of chloride. Statistically significant downward trends in flow-weighted fecal indicator bacteria Escherichia coli (E. coli) population densities were noted for Rock Creek and the down-stream site on the Little Blue River. However, no trend was identified in E. coli population density at the upstream Little Blue River site. The downward trend in E. coli population density at the downstream site could be a result of decreased streamflow and precipitation over the study period, storage of fecal indicator bacteria in the Little Blue River streambed within the study area, die-off of fecal indicator bacteria during travel from upstream to downstream, changes in the sample collection methodology, improvements to the city’s storm-water and wastewater infrastructures, or a combination of these factors. The statistically significant downward trend in suspended-sediment concentration identified at the upstream Little Blue River site could be affected by the decreased streamflow and precipitation during the study period, by changes in sampling methods within the study period, and by the decrease in construction and urban land development upstream from the city. No statistically significant change was indicated in the annual suspended-sediment load transported from Independence to the Little Blue River during the study period. More than one-half the suspended sediment transported in the Little Blue River originated in the watershed upstream from Independence. The Little Blue River and many of its tributaries that drain Independence have been designated as recreational waters classified for whole-body contact class B and secondary contact recreation, and some have been listed as impaired for E. coli by the Missouri Department of Natural Resources from urban runoff and storm sewers. Observations were made among the available E. coli population density data for both Little Blue River sites to further understand water-quality conditions over the study period. Both Little Blue River sites had similar medians and geometric means for the recreational season (April through October) and during the full study period, both of which are greater than the regulatory population density for both recreational classes. The Little Blue River drainage area nearly doubles in size from the upstream to downstream site; therefore, the consistent geometric mean and median of E. coli population densities at the upstream and downstream Little Blue River sites could be primarily due to the larger volume of streamflow creating a dilution effect. Other possible factors could be storage of fecal indicator bacteria in stream bed sediments, die-off of fecal indicator bacteria during transport, improvements to the city’s wastewater and stormwater infrastructure, changes to sampling methodology, or a combination of these factors. Specific sources of the E. coli are currently (2019) unknown.

Missouri↗
USGS1978

Morphology of chasma walls, Mars

The landforms developed on the walls of the Valles Marineris system of chasmas are of three major types, which are locally transitional. The most common type is composed of steep spurs and gullies. The dominant process in the formation or modification of this type appears to be the downslope movement of. material under the influence of gravity, resulting in the accumulation of extensive talus deposits. The type is morphologically similar to high, steep terrestrial scarps in desert or alpine environments. The second morphologic type consists of walls dissected by tributary canyons with characteristic V-shaped cross profiles and blunt canyon heads that locally contain lobate deposits. The tributary canyons may be relict features of the time, when the existence of running water was possible on the surface of Mars. The third morphologic type consists of landslide scars forming broad curved or straight recessed sections of chasma wall. This type is accompanied by landslide deposits that form hummocky floors at the base of the recessed sections. The landslides developed at the expense of other wall morphologies. Chains of rimless depressions and craters that parallel the main structural trends of the chasmas are best interpreted as collapse holes. The origin of the chasmas on Mars is conjectural and may have been structural (grabens), but, on the basis of morphologic studies of their walls, it is suggested that most of the present wall configuration is the result of erosional scarp retreat, where erosion follows preestablished structural planes of weakness.

Journal of Research of the U.S. Geological Survey↗
USGS1959

Geology and quicksilver deposits of the Terlingua district, Texas

The Terlingua quicksilver district, which has produced more than 150,000 flasks of quicksilver, is in the southern part of the Big Bend region of southwestern Texas. It is a narrow, eastwest area about 20 miles long and lies mainly in southwestern Brewster County. The district is connected by graded road with the nearest railroad, 84 miles north of its center. Quicksilver minerals were first discovered in the district in the latter part of the 19th century, but there was no substantial production until 1900. Although there are about 20 mines and many prospects, more than 90 percent of the quicksilver came from the Chisos-Rainbow, Mariposa, and Study Butte mines. The most productive years were during World War I; since 1946 the district has been idle. Future production depends upon the discovery of new ore bodies-which will be costly-and the working of deposits now considered of too low grade to be profitable.

Texas↗
USGS1994

'The Kesterson effect'

Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the 'Kesterson effect.' At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California, in California, selenium as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.

California↗
USGS2012

Active tectonic and magmatic processes beneath Long Valley Caldera, eastern California: An overview

Geological, chronological, and structural studies of the Long Valley-Mono/Inyo Craters area document a long history of related volcanic eruptions and earthquakes controlled by regional extensional tectonics of the Basin and Range province. This activity has persisted for hundreds of thousands of years and is likely to continue. The Long Valley magma chamber had a volume approaching 3000 km 3 prior to its climatic caldera-forming eruption 0.7 m.y. ago but has been reduced to less than a third of this volume by cooling, eruption, and crystallization. Seismic evidence indicates that the main mass of the present Long Valley magma chamber is about 10 km in diameter and that its roof is 8–10 km deep with smaller cupolas as shallow as 4–5 km. Although a chamber of this size is probably capable of producing an eruption approaching 30 km 3 of lava, the record over the past 0.5 m.y. suggests that eruptions of 1 km 3 or less are far more likely. Models proposed for the current ground uplift and seismicity within the caldera require inflation of 0.1–0.2 km 3 by additional magma since mid-1979, and some models suggest that inflation was accompanied by injection of a thin dike or dikes (probably of silicic magma) into the ring fracture zone beneath the south moat. Several of the M 5.8–6.2 earthquakes that occurred in the region beginning in 1978 had non-double-couple focal mechanisms. Whether these unusual mechanisms indicate injection of mafic (low-viscosity) magma at midcrustal depths in the Sierra Nevada block south of the caldera remains debatable. Studies of calderas of various ages throughout the world indicate that episodes of unrest are relatively common and do not invariably culminate in eruptions. Although current unrest is concentrated in the south moat of Long Valley caldera, the Inyo/Mono Craters probably hold a greater potential for producing an eruption in the foreseeable future. The Inyo/Mono Craters have erupted at 500-year intervals over the past 2000–3000 years, whereas the Long Valley magma chamber has erupted at about 200,000-year intervals over the past 700,000 years. In either case, a major earthquake near the caldera could strongly influence the course of volcanic activity.

Journal of Geophysical Research Solid Earth↗
USGS2007

Scoping of Flood Hazard Mapping Needs for Hancock County, Maine

Background The Federal Emergency Management Agency (FEMA) developed a plan in 1997 to modernize the FEMA flood mapping program. FEMA flood maps delineate flood hazard areas in support of the National Flood Insurance Program (NFIP). FEMA's plan outlined the steps necessary to update FEMA's flood maps for the nation to a seamless digital format and streamline FEMA's operations in raising public awareness of the importance of the maps and responding to requests to revise them. The modernization of flood maps involves conversion of existing information to digital format and integration of improved flood hazard data as needed. To determine flood mapping modernization needs, FEMA has established specific scoping activities to be done on a county-by-county basis for identifying and prioritizing requisite flood-mapping activities for map modernization. The U.S. Geological Survey (USGS), in cooperation with FEMA and the Maine Floodplain Management Program (MFMP) State Planning Office, began scoping work in 2006 for Hancock County. Scoping activities included assembling existing data and map needs information for communities in Hancock County, documentation of data, contacts, community meetings, and prioritized mapping needs in a final scoping report (this document), and updating the Mapping Needs Update Support System (MNUSS) database with information gathered during the scoping process. The average age of the FEMA floodplain maps (all types) in Hancock County, Maine, is at least 19 years. Most of these studies were published in the late 1980s and early 1990s, and no study is more recent than 1992. Some towns have partial maps that are more recent than their study, indicating that the true average age of the data is probably more than 19 years. Since the studies were done, development has occurred in some of the watersheds and the characteristics of the watersheds have changed. Therefore, many of the older studies may not depict current conditions or accurately estimate risk in terms of flood heights or flood mapping.

Open-File Report↗
USGS1985

Preliminary report on a study to estimate flood volumes of small rural streams in Ohio: Methods, site selection, and data base

In 1981, the U.S. Geological Survey, in cooperation with the Ohio Department of Transportation and the Federal Highway Administration, began a 7-year flood-volume study of small rural basins in Ohio. This report summarizes the methods of study and describes reconnaissance and site-selection procedures, locations and characteristics of the stations, instrumentation, and methods of collecting and storing data. The first phase of this study involved an intensive field reconnaissance of about 7,000 sites, of which 32 basins were selected for detailed analysis. Drainage areas for the basins varied from 0.13 to 6.45 square miles, and main-channel slopes ranged from 7.6 to 276 feet per mile. Five years of 5-minute rainfall-runoff data will be colledted for each study site. These data will be used to calibrate and verify a rainfall-runoff model for each basin. The calibrated model will be used in conjunction with 80 years of National Weather Service 5-minute precipitation data to synthesize a representative 80-year streamflow record at each site. A Log-Pearson Type III frequency distribution will be applied to each record to define the magnitudes and frequencies of flood volumes at each site. These data will be used to develop regionalized multiple regression models for estimating flood-volume magnitudes and frequencies at small rural ungaged sites in Ohio. The report also summarizes rainfall-runoff data collected from July 1981 through September 1983, but does not interpret the data. An average of eleven event periods per site were monitored where maximum 5-minute rainfall intensities varied from 0.02 to .067 inches and maximum peak discharges varied from 1 to 1,130 cubic feet per second.

Ohio↗
USGS2006

Losses and Gains for Eight Unlined Canals Along the Purgatoire River near Trinidad, Colorado, 2000-2004

The U.S. Geological Survey conducted a field study from July 2000 through June 2004, in cooperation with the Purgatoire River Water Conservancy District, Colorado Water Conservation Board, and Bureau of Reclamation, to characterize and quantify losses and gains in Picketwire, Baca, El Moro, Chilili, Enlarged Southside, Model, John Flood, and Hoehne irrigation canals. These canals divert streamflow from the Purgatoire River between Trinidad Dam and the city of Hoehne, Colorado. Discharge measurements were made along the eight canals during steady-state conditions to identify subreaches with losses or gains. Losses and gains were computed between main-channel measurement sites along each canal by equating inflows to outflows plus flow loss or gain in the subreach. As part of this study, multiple discharge measurements also were made at Picketwire, El Moro, Chilili, Enlarged Southside, Model, John Flood, and Hoehne canal headgates to compare standard Parshall flume-rated and measured discharge at the canal headgates. Results from the discharge measurements showed that Picketwire, Chilili, and Hoehne Canals generally lose flow from the headgate to the end of the canal, although some subreaches showed gains during some measurements. Losses in Picketwire Canal ranged from about 7 percent to about 23 percent of the headgate inflow, and Chilili Canal losses ranged from about 2 percent to about 34 percent of the headgate inflow. Hoehne Canal losses ranged from only about 2 to 7 percent of the headgate inflow, which is within the uncertainty of the measurements. El Moro Canal appears to lose flow in some subreaches and gain flow in other subreaches. Despite gains in some subreaches, measurements show flow losses of about 28 percent of the headgate inflow for the entire El Moro Canal. Losses and gains in Baca, Picketwire, Chilili, and Enlarged Southside canals may be affected by the length of time that the canal has been flowing. Losses in these canals appear to decrease the longer the canal has been continuously flowing. In some cases, subreaches of some of these canals go from losing to gaining flow. Unlike some of the other canals, losses and gains in El Moro and John Flood Canal do not appear to be related to how long the canal was flowing before the measurements were made. Losses and gains in El Moro Canal are probably related to the physical attributes of the canal, such as the canal construction and proximity to other canals. Field data indicate that El Moro Canal gains flow from and loses flow to other canals. Measurements made from the Model Canal headgate to Model Reservoir show canal losses and gains ranging from 1 to 5 percent of the headgate inflow, which is less than the uncertainty of the measurements. However, measured canal losses and gains from Model Canal downstream from Model Reservoir ranged from a loss of 59 percent to a gain of 1 percent of the subreach inflow. Measured discharges at the canal headgates were usually higher than the discharges determined using the standard Parshall flume discharge tables. Of the 102 discharge measurements made at the canal headgates, 72 of the measured discharges were higher than the corresponding discharges determined using the standard Parshall flume discharge tables. This means that about 70 percent of the time, the amount of flow that was diverted into the canals was underreported. All measured discharges at the Picketwire and El Moro headgates were higher than the corresponding flume-rated discharges, and all but one measured discharge at the Chilili headgate were higher than the corresponding flume-rated discharges. Discharges measured at the remaining headgates varied from 14 percent lower to 27 percent higher than the corresponding flume-rated discharges.

Scientific Investigations Report↗
USGS1978

Report on laboratory testing of shallow sediments, Middle Atlantic Outer Continental Shelf

This report contains the results of geotechnical engineering testing on cores taken by the U.S. Geological Survey to evaluate the characteristics of the sea floor within the Baltimore Canyon Trough area. The coring took place in September, 1977 aboard the R/V ANNANDALE. During the cruise (AN-01-77), 20 vibracores were taken at 17 stations across the Continental Shelf off the coast of New Jersey (Figure 1). Table 1 shows the station locations, the water depths at each station, and the core lengths. The objective of the study was to obtain a set of representative index properties as well as strength and compressibility data on sediments from across the shelf in the Baltimore Canyon Trough area. It was anticipated that these data, although of a reconnaissance rather than a site-specific nature, would provide a useful indication of the engineering properties of these sediments. Ultimately, these data may be used for preliminary design applications and the assessment of potential hazards. In this report, the results are presented without any interpretation. An overall evaluation of all data collected during the study, including those contained in this report, presently is underway. Users of this report should be cautioned not to take these test results out of context. Two factors must be borne in mind. The first is that these tests were done on somewhat disturbed samples compared with those obtained through high-quality sampling programs onshore. Much disturbance is inevitable offshore but the significance of the disturbance on these test results has not yet been evaluated. The second factor is that these data are only part of the total set available from this project. A complete analysis of all data may lead to conclusions that are different from those based on this set of data only. The tests reported herein were performed by Geotechnical Engineers Inc., 1017 Main Street, Winchester, Massachusetts 01890, under Contract 14-08-0001-16232 of the U.S. Geological Survey. Richard Brown and Charles Osgood performed the engineering properties tests. Sally A. Wood of the U.S. Geological Survey handled the transfer of vibracores between the U.S. Geological Survey and Geotechnical Engineers Inc. and, also, assisted in the preparation of this report.

Open-File Report↗
USGS2005

Eastern rim of the Chesapeake Bay impact crater: Morphology, stratigraphy, and structure

This study reexamines seven reprocessed (increased vertical exaggeration) seismic reflection profiles that cross the eastern rim of the Chesapeake Bay impact crater. The eastern rim is expressed as an arcuate ridge that borders the crater in a fashion typical of the "raised" rim documented in many well preserved complex impact craters. The inner boundary of the eastern rim (rim wall) is formed by a series of raterfacing, steep scarps, 15-60 m high. In combination, these rim-wall scarps represent the footwalls of a system of crater-encircling normal faults, which are downthrown toward the crater. Outboard of the rim wall are several additional normal-fault blocks, whose bounding faults trend approximately parallel to the rim wall. The tops of the outboard fault blocks form two distinct, parallel, flat or gently sloping, terraces. The innermost terrace (Terrace 1) can be identified on each profile, but Terrace 2 is only sporadically present. The terraced fault blocks are composed mainly of nonmarine, poorly to moderately consolidated, siliciclastic sediments, belonging to the Lower Cretaceous Potomac Formation. Though the ridge-forming geometry of the eastern rim gives the appearance of a raised compressional feature, no compelling evidence of compressive forces is evident in the profiles studied. The structural mode, instead, is that of extension, with the clear dominance of normal faulting as the extensional mechanism.

Chesapeake Bay↗