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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 847 records · Page 47Linked to original sources

USGS1989

Preliminary map of upper Eocene to Holocene volcanic and related rocks of the Cascade Range, Oregon

Since 1979 the Geothermal Research Program of the U.S. Geological Survey has carried out multidisciplinary research in the Cascade Range. The goal of this research is to understand the geology, tectonics, and hydrology of the Cascades in order to characterize and quantify geothermal resource potential. A major goal of the program is compilation of a comprehensive geologic map of the entire Cascade Range that incorporates modern field studies and that has a unified and internally consistent explanation.

Oregon↗

USGS1996

Geohydrology of the Island of Oahu, Hawaii

The island of Oahu, Hawaii, is the eroded remnant of two coalesced shield volcanoes, the Waianae Volcano and the Koolau Volcano. Shield-building lavas emanated mainly from the rift zones of the volcanoes. Subaerial eruptions of the Waianae Volcano occurred between 3.9 and 2.5 million years ago, and eruptions of the Koolau Volcano occurred between 2.6 and 1.8 million years ago. The volcanoes have subsided more then 6,000 feet, and erosion has destroyed all but the western rim of the Koolau Volcano and the eastern part of the Waianae Volcano, represented by the Koolau and Waianae Ranges, respectively. Hydraulic properties of the volcanic-rock aquifers are determined by the distinctive textures and geometry of individual lava flows. Individual lava flows are characterized by intergranular, fracture, and conduit-type porosity and commonly are highly permeable. The stratified nature of the lava flows imparts a layered heterogeneity. The flows are anisotropic in three dimensions, with the largest permeability in the longitudinal direction of the lava flow, an intermediate permeability in the direction transverse to the flow, and the smallest permeability normal to bedding. Averaged over several lava-flow thicknesses, lateral hydraulic conductivity of dike-free lava flows is about 500 to 5,000 feet per day, with smaller and larger values not uncommon. Systematic areal variations in lava-flow thickness or other properties may impart trends in the heterogeneity. The aquifers of Oahu contain two flow regimes: shallow freshwater and deep saltwater. The freshwater floats on underlying saltwater in a condition of buoyant displacement, although the relation is not necessarily a simple hydrostatic balance everywhere. Natural driving mechanisms for freshwater and saltwater flow differ. Freshwater moves mainly by simple gravity flow; meteoric water flows from inland recharge areas at higher altitudes to discharge areas at lower altitudes near the coast. Remnant volcanic heat also may drive geothermal convection of freshwater in the rift zones. Saltwater flow is driven by changes in freshwater volume and sea level and by dispersive and geothermal convection. Freshwater flow is much more active--velocity is higher and residence time is shorter--than saltwater flow. Hydrodynamic dispersion produces a transition zone of mixed water between the freshwater and the underlying saltwater. The Waianae aquifer in the Waianae Volcanics and the Koolau aquifer in the Koolau Basalt are the two principal volcanic-rock aquifers on Oahu. The sequences of coastal-plain and valley-fill deposits locally form aquifers, but these aquifers are of minor importance because of the small volume of water contained in them. The two principal volcanic-rock aquifers are composed mainly of thick sequences of permeable, thin-bedded lava flows. These aquifers combine to form a layered aquifer system throughout central Oahu where the Koolau aquifer overlies the Waianae aquifer. They are separated by a regional confining unit formed by weathering along the Waianae-Koolau unconformity, which marks the eroded and weathered surface of the Waianae Volcano buried by younger Koolau lava flows. The areal hydraulic continuity of the aquifers of Oahu is interrupted in many places by steeply dipping, stratigraphically unconformable, geohydrologic barriers. These low-permeability features include eruptive feeder dikes, sedimentary valley fills, and former erosional surfaces now buried by younger lava flows or sediments. The barriers impede and divert lateral ground-water flow and impound ground water to greater heights than would occur in the absence of the barriers, causing abrupt stepped discontinuities in the potentiometric surface. The largest discontinuities are associated with dense concentrations of dikes in the eruptive rift zones of each volcano. The dikes in these zones originate from great depths and impede flow both in shallow-freshwater and in deep-saltwater flow sy

Professional Paper↗

USGS2007

Thermal Methods for Investigating Ground-Water Recharge

Recharge of aquifers within arid and semiarid environments is defined as the downward flux of water across the regional water table. The introduction of recharging water at the land surface can occur at discreet locations, such as in stream channels, or be distributed over the landscape, such as across broad interarroyo areas within an alluvial ground-water basin. The occurrence of recharge at discreet locations is referred to as focused recharge, whereas the occurrence of recharge over broad regions is referred to as diffuse recharge. The primary interest of this appendix is focused recharge, but regardless of the type of recharge, estimation of downward fluxes is essential to its quantification. Like chemical tracers, heat can come from natural sources or be intentionally introduced to infer transport properties and aquifer recharge. The admission and redistribution of heat from natural processes such as insolation, infiltration, and geothermal activity can be used to quantify subsurface flow regimes. Heat is well suited as a ground-water tracer because it provides a naturally present dynamic signal and is relatively harmless over a useful range of induced perturbations. Thermal methods have proven valuable for recharge investigations for several reasons. First, theoretical descriptions of coupled water-and-heat transport are available for the hydrologic processes most often encountered in practice. These include land-surface mechanisms such as radiant heating from the sun, radiant cooling into space, and evapotranspiration, in addition to the advective and conductive mechanisms that usually dominate at depth. Second, temperature is theoretically well defined and readily measured. Third, thermal methods for depths ranging from the land surface to depths of hundreds of meters are based on similar physical principles. Fourth, numerical codes for simulating heat and water transport have become increasingly reliable and widely available. Direct measurement of water flux in the subsurface is difficult, prompting investigators to pursue indirect methods. Geophysical approaches that exploit the coupled relation between heat and water transport provide an attractive class of methods that have become widely used in investigations of recharge. This appendix reviews the application of heat to the problem of recharge estimation. Its objective is to provide a fairly complete account of the theoretical underpinnings together with a comprehensive review of thermal methods in practice. Investigators began using subsurface temperatures to delineate recharge areas and infer directions of ground-water flow around the turn of the 20th century. During the 1960s, analytical and numerical solutions for simplified heat- and fluid-flow problems became available. These early solutions, though one-dimensional and otherwise restricted, provided a strong impetus for applying thermal methods to problems of liquid and vapor movement in systems ranging from soils to geothermal reservoirs. Today?s combination of fast processors, massive data-storage units, and efficient matrix techniques provide numerical solutions to complex, three-dimensional transport problems. These approaches allow researchers to take advantage of the considerable information content routinely achievable in high-accuracy temperature work.

Professional Paper↗

USGS2014

Thermal maturity patterns in Pennsylvanian coal-bearing rocks in Alabama, Tennessee, Kentucky, Virginia, West Virginia, Ohio, Maryland, and Pennsylvania

Thermal maturation patterns of Pennsylvanian strata in the Appalachian basin and part of the Black Warrior basin were determined by compiling previously published and unpublished percent-vitrinite-reflectance (%R 0 ) measurements and preparing isograd maps on the basis of the measurements. The isograd values range from 0.6 %R 0 in Ohio and the western side of the Eastern Kentucky coal field to 5.5 %R 0 in the Southern field in the Pennsylvania Anthracite region, Schuylkill County, Pa. The vitrinite-reflectance values correspond to the American Society of Testing Materials (ASTM) coal-rank classes of high-volatile C bituminous to meta-anthracite, respectively. In general, the isograds show that thermal maturity patterns of Pennsylvanian coals within the Appalachian basin generally decrease from east to west. In the Black Warrior basin of Alabama, the isograds show a circular pattern with the highest values (greater than 1.6 %R 0 ) centered in Jefferson County, Ala. Most of the observed patterns can be explained by variations in the depth of burial, variations in geothermal gradient, or a combination of both; however, there are at least four areas of higher ranking coal in the Appalachian basin that are difficult to explain by these two processes alone: (1) a set of west- to northwest-trending salients centered in Somerset, Cambria, and Fayette Counties, Pa.; (2) an elliptically shaped, northeast-trending area centered in southern West Virginia and western Virginia; (3) the Pennsylvania Anthracite region in eastern Pennsylvania; and (4) the eastern part of the Black Warrior coal field in Alabama. The areas of high-ranking coal in southwestern Pennsylvania, the Black Warrior coal field, and the Pennsylvania Anthracite region are interpreted here to represent areas of higher paleo-heat flow related to syntectonic movement of hot fluids towards the foreland associated with Alleghanian deformation. In addition to the higher heat flow from these fluids, the Pennsylvania Anthracite region also was buried more deeply than other parts of the Appalachian basin. The area of high rank coal in southwestern Virginia probably was controlled primarily by overburden thickness, but may also have been influenced by higher geothermal gradients.

Appalacian basin↗

USGS2019

Evaluation of chemical and hydrologic processes in the eastern Snake River Plain Aquifer based on results from geochemical modeling, Idaho National Laboratory, eastern Idaho

Nuclear research activities at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) produced liquid and solid chemical and radiochemical wastes that were disposed to the subsurface resulting in detectable concentrations of some waste constituents in the eastern Snake River Plain (ESRP) aquifer. These waste constituents may affect the water quality of the aquifer and may pose risks to the eventual users of the aquifer water. To understand these risks to water quality the U.S. Geological Survey, in cooperation with the DOE, conducted geochemical mass-balance modeling of the ESRP aquifer to improve the understanding of chemical reactions, sources of recharge, mixing of water, and groundwater flow directions in the shallow (upper 250 feet) aquifer at the INL. Modeling was conducted using the water chemistry of 127 water samples collected from sites at and near the INL. Water samples were collected between 1952 and 2017 with most of the samples collected during the mid-1990s. Geochemistry and isotopic data used in geochemical modeling consisted of dissolved oxygen, carbon dioxide, major ions, silica, aluminum, iron, and the stable isotope ratios of hydrogen, oxygen, and carbon. Geochemical modeling results indicated that the primary chemical reactions in the aquifer were precipitation of calcite and dissolution of plagioclase (An 60 ) and basalt volcanic glass. Secondary minerals other than calcite included calcium montmorillonite and goethite. Reverse cation exchange, consisting of sodium exchanging for calcium on clay minerals, occurred near site facilities where large amounts of sodium were released to the ESRP aquifer in wastewater discharge. Reverse cation exchange acted to retard the movement of wastewater-derived sodium in the aquifer. Regional groundwater inflow was the primary source of recharge to the aquifer underlying the Northeast and Southeast INL Areas. Birch Creek (BC), the Big Lost River (BLR), and groundwater from BC valley provided recharge to the North INL Area, and the BLR and groundwater from BC and Little Lost River (LLR) valleys provided recharge to the Central INL Area. The BLR, groundwater from the BLR and LLR valleys and the Lost River Range, and precipitation provided recharge to the Northwest and Southwest INL Areas. The primary source of recharge west and southwest of the INL was groundwater inflow from BLR valley. Upwelling geothermal water was a small source of recharge at two wells. Aquifer recharge from surface water in the northern, central, and western parts of the INL indicated that the aquifer in these areas was a dynamic, open system, whereas the aquifer in the eastern part of the INL, which receives little recharge from surface water, was a relatively static and closed system. Sources of recharge identified from isotope ratios and geochemical modeling (major ion concentrations) were nearly identical for the North, Northeast, Southeast, and Central INL Areas, which indicated that both methods probably accurately identified the sources of recharge in these areas. Conversely, isotope ratios indicated that the BLR and groundwater from the LLR valley provided most recharge to the western parts of the Northwest and Southwest INL Areas, whereas geochemical modeling results indicated a smaller area of recharge from the BLR and groundwater from the LLR valley, a larger area of recharge from the Lost River Range, and recharge of groundwater from the BLR valley that extended to the west INL boundary. The results from geochemical modeling probably were more accurate because major ion concentrations, but not isotope ratios, were available to characterize groundwater from the BLR valley and the Lost River Range. Sources of recharge identified with a groundwater flow model (using particle tracking) and geochemical modeling were similar for the Northeast and Southeast INL Areas. However, differences between the models were that the geochemical model represented (1) recharge of groundwater from the Lost River Range in the western part of the INL, whereas the flow model did not, (2) recharge of groundwater from the BC and BLR valleys extending farther south and east, respectively, than the flow model, and (3) more recharge from the BLR in the Southwest INL Area than the flow model. Mixing of aquifer water beneath the INL included (1) mixing of regional groundwater and water from the BC valley in the Northeast and Southeast INL Areas and (2) mixing of surface water (primarily from the BLR) and groundwater across much of the North, Central, Northwest, and Southwest INL Areas. Localized recharge from precipitation mixed with groundwater in the Northwest and Southwest INL Areas, and localized upwelling geothermal water mixed with groundwater in the Central and Northeast INL Areas. Flow directions of regional groundwater were south in the eastern part of the INL and south-southwest at downgradient locations. Groundwater from the BC and LLR valleys initially flowed southeast before changing to south-southwest flow directions that paralleled regional groundwater, and groundwater from the BLR valley initially flowed south before changing to a southsouthwest direction. Wastewater-contaminated groundwater flowed south from the Idaho Nuclear Technology and Engineering Center (INTEC) infiltration ponds in a narrow plume, with the percentage of wastewater in groundwater decreasing due to dilution, dispersion, and (or) degradation from about 60‒80 percent wastewater 0.7‒0.8 mile (mi) south of the INTEC infiltration ponds to about 1.4 percent wastewater about 15.5 mi south of the INTEC infiltration ponds. Wastewater contaminated groundwater flowed southeast and then southwest from the Naval Reactors Facility industrial waste ditch, with the percentage of wastewater in groundwater decreasing from about 100 percent wastewater adjacent to the waste ditch to about 2 percent wastewater about 0.6 mi south of the waste ditch.

Idaho↗

USGS2024

Temporal, spatial, and chemical evolution of Quaternary high-silica rhyolites in the Mineral Mountains, Utah

The Mineral Mountains in southwestern Utah are a structurally controlled core complex at the confluence of the Colorado Plateau and the Basin and Range physiographic provinces. Aside from hosting Utah’s largest batholith, the Mineral Mountains host some of the State’s youngest high-silica rhyolites, which have been linked to a magma source that is presently being utilized as an enhanced geothermal system. The high-silica rhyolites take the form of effusive lavas and domes, and explosive products are rare. Previous K-Ar dating of these Pleistocene rhyolites placed eruptions between about 790 and 500 kilo-annum (ka) with contemporaneous basalts erupting in the valley to the east of the Mineral Mountains. Large uncertainties on these ages obscured the tempo of eruptions and thus hindered attempts to constrain the timescales of the petrogenetic processes that produced the rhyolites. In this study, we build on previous studies conducted in the 1970s and 1980s by using new geochronologic and geochemical data to investigate the temporal and spatial evolution of the youngest phase of volcanism in the Mineral Mountains. We identify two major eruptive periods, from approximately 850 to 750 ka and from approximately 590 to 480 ka. The older phase is characterized by the eruption of several basaltic lavas, two obsidian flows, and a series of coalescing porphyritic rhyolite domes. The younger phase included the eruption of six evolved high-silica rhyolite domes and one pyroclastic deposit, followed by the eruption of trachyandesite in the adjacent valley to the east. Whole-rock geochemical data indicate that the rhyolites can be divided into three chemical groups, with more evolved compositions erupting through time. The youngest rhyolites along the range crest have the lowest total iron and TiO 2 concentrations and the highest incompatible element concentrations, indicative of increasing differentiation with time and elevation. Improved precision on the eruption ages indicates a recurrence interval of approximately 20 thousand years. The eruptive flux for both periods of rhyolitic volcanism is about 0.01 cubic kilometers per thousand years, which is less than the magma resurgence flux rates for syn-caldera and post-caldera eruptions of the Valles Caldera and Yellowstone Caldera volcanic systems. Collectively, these geochemical, geochronological, and volumetric data may facilitate a better understanding of heat flux and the longevity of magmatic sources related to geothermal resources in similar small-volume, silicic systems.

Utah↗

USGS2008

Geologic map of Mount Mazama and Crater Lake Caldera, Oregon, including the database for the geologic map of Mount Mazama and Crater Lake Caldera, Oregon

Crater Lake partly fills one of the most spectacular calderas of the world, an 8-by-10-km basin more than 1 km deep formed by collapse of the volcano known as Mount Mazama (fig. 1) during a rapid series of explosive eruptions about 7,700 years ago. Having a maximum depth of 594 m, Crater Lake is the deepest lake in the United States. Crater Lake National Park, dedicated in 1902, encompasses 645 km2 of pristine forested and alpine terrain, including the lake itself, virtually all of Mount Mazama, and most of the area of the geologic map. The geology of the area was first described in detail by Diller and Patton (1902) and later by Williams (1942), whose vivid account led to international recognition of Crater Lake as the classic collapse caldera. Because of excellent preservation and access, Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. For example, the climactic ejecta are renowned among volcanologists as evidence for systematic compositional zonation within a subterranean magma chamber. Mount Mazama's climactic eruption also is important as the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore. A detailed bathymetric survey of the floor of Crater Lake in 2000 (Bacon and others, 2002) provides a unique record of postcaldera eruptions, the interplay between volcanism and filling of the lake, and sediment transport within this closed basin. Knowledge of the geology and eruptive history of the Mount Mazama edifice, greatly enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve. Lastly, the many smaller volcanoes of the High Cascades beyond the limits of Mount Mazama are a source of information on the flux of mantle-derived magma through the region. General principles of magmatic and eruptive processes revealed by the present study have been incorporated not only in scientific investigations elsewhere, but in the practical evaluation of hazards (Bacon and others, 1997b) and geothermal resources (Bacon and Nathenson, 1996) in the Crater Lake region. In addition to papers in scientific journals, field trip guides, and the hazard and geothermal reports, the major product of this long-term study of Mount Mazama is the geologic map. The map is unusual because it portrays bedrock (outcrop), surficial, and lake floor geology. Caldera wall geology is depicted in detail on the accompanying geologic panoramas.

Oregon↗

USGS2019

Three-dimensional geologic map of the southern Carson Sink, Nevada, including the Fallon FORGE area

The three-dimensional (3–D) geologic map characterizes the subsurface in the southern Carson Sink region. We created the 3–D map by integrating the results from seismic-reflection, potential-field-geophysical, and lithologic well-logging investigations completed in and around the Fallon FORGE site as part of the U.S. Department of Energy Frontier Observatory for Research in Geothermal Energy (FORGE) initiative from 2015–2018. The FORGE initiative was part of an effort to develop the technologies, techniques, and knowledge needed to make enhanced geothermal systems a commercially viable electricity-generation option for the United States. Geologic units and structures mapped during the Fallon FORGE study, which particularly focused on the Mesozoic basement, were extrapolated to create the 3–D map of the southern Carson Sink area. The 3–D map area is 10 km wide along the east-west and north-south axes and extends 2.5 km below sea level, ~3.7 km below the land surface. Views of the map include horizontal and vertical sections and oblique perspective views from several angles. We describe the geologic units and structures and discuss the methods used to integrate the geologic and geophysical information in a 3–D geologic interpretation. We provide digital data for elements of the map, such as individual 3–D fault and stratigraphic surfaces and surface-fault traces. Input data are available from various data repositories through cited web links. A brief movie displaying the 3–D map is available at https://doi.org/10.3133/sim3437 .

Nevada↗

USGS2006

Volcano and Earthquake Monitoring Plan for the Yellowstone Volcano Observatory, 2006-2015

To provide Yellowstone National Park (YNP) and its surrounding communities with a modern, comprehensive system for volcano and earthquake monitoring, the Yellowstone Volcano Observatory (YVO) has developed a monitoring plan for the period 2006-2015. Such a plan is needed so that YVO can provide timely information during seismic, volcanic, and hydrothermal crises and can anticipate hazardous events before they occur. The monitoring network will also provide high-quality data for scientific study and interpretation of one of the largest active volcanic systems in the world. Among the needs of the observatory are to upgrade its seismograph network to modern standards and to add five new seismograph stations in areas of the park that currently lack adequate station density. In cooperation with the National Science Foundation (NSF) and its Plate Boundary Observatory Program (PBO), YVO seeks to install five borehole strainmeters and two tiltmeters to measure crustal movements. The boreholes would be located in developed areas close to existing infrastructure and away from sensitive geothermal features. In conjunction with the park's geothermal monitoring program, installation of new stream gages, and gas-measuring instruments will allow YVO to compare geophysical phenomena, such as earthquakes and ground motions, to hydrothermal events, such as anomalous water and gas discharge. In addition, YVO seeks to characterize the behavior of geyser basins, both to detect any precursors to hydrothermal explosions and to monitor earthquakes related to fluid movements that are difficult to detect with the current monitoring system. Finally, a monitoring network consists not solely of instruments, but requires also a secure system for real-time transmission of data. The current telemetry system is vulnerable to failures that could jeopardize data transmission out of Yellowstone. Future advances in monitoring technologies must be accompanied by improvements in the infrastructure for data transmission. Overall, our strategy is to (1) maximize our ability to provide rapid assessments of changing conditions to ensure public safety, (2) minimize environmental and visual impact, and (3) install instrumentation in developed areas.

Scientific Investigations Report↗

USGS2024

Dissolved arsenic concentrations in surface waters within the upper portions of the Klamath River Basin, Oregon and California

Arsenic toxicity is an environmental health problem. Levels of arsenic in surface waters at some locations in the Klamath River Basin in southern Oregon and northern California can exceed the U.S. Environmental Protection Agency (EPA) standard for drinking water. There are both anthropogenic and natural sources of arsenic. The Klamath River Basin consists primarily of volcanic deposits and contains an underground geothermal system with hot springs and warm water wells, all known natural sources of arsenic. Anthropogenic sources of arsenic are related to the agricultural use of herbicides, fungicides, and insecticides. Surface water arsenic levels can also be affected by fertilizer amendments, evaporative concentration, oxygen-level depletion, and various geochemical transformations that can increase arsenic mobilization. In this study by the U.S. Geological Survey and the Bureau of Reclamation, dissolved concentrations of arsenic, copper, and lead were measured in surface waters at 39 unique sites within the upper portions of the Klamath River Basin between 2018 and 2022. In every year, except 2022, sites were sampled four times between April and November. Surface-water arsenic concentrations varied up to four-orders of magnitude among sites. Median arsenic concentration was lowest at Cherry Creek (0.03 micrograms per liter [μg/L]) and highest at Wood Kimball Spring (36.7 μg/L), two sites located north of Upper Klamath Lake. The highest arsenic concentrations (17.4±4.9 μg/L, n =3) were found in drain sites (defined here as a waterbody returning used irrigation water) while the lowest arsenic concentrations were found in an artesian well (0.8 μg/L, n =1). The elevated arsenic concentrations of the drain sites suggest that arsenic might be concentrated or mobilized by agricultural activities, water re-use practices, and (or) by geochemical processes occurring around water stored in drains (that is, in the water column and across sediment water boundaries). A source of arsenic in drain water in the Klamath Strait Drain area includes water used for irrigation originating from Ady Canal. Other potential sources include groundwater, geothermal water, and local soils and sediments. Seasonal differences in surface-water arsenic concentrations were detected at 13 sites, 10 of which had higher arsenic concentrations in summer than in either spring or fall. The sites sampled around Upper Klamath Lake, the impounded rivers, one of the two canal sites, and 5 of the 14 river sites had higher surface-water arsenic concentrations in the summer than in either spring or fall. Surface-water arsenic concentrations from groundwater sources (that is, springs and in the artesian well) did not vary significantly among seasons (p-values greater than 0.1). Median surface-water concentrations of copper and lead ranged from 0.03 to 3.7 μg/L, and from 0.013 to 0.175 μg/L ( n =2–18), respectively. Dissolved concentrations of both metals were below acute toxicity endpoints reported by the EPA for freshwater animals. Surface-water arsenic concentrations varied independently from corresponding changes in surface-water lead or copper concentrations. However, arsenic concentrations measured in bed-sediment samples collected from a subset of sites located north of Upper Klamath Lake correlated strongly and significantly with the corresponding sedimentary lead concentrations ( p =0.015). Aqueous arsenic speciation measured in a subset of sites in 2019 and 2022 showed that all the arsenic existed as arsenic (V), the most oxidized arsenic species, and presumably, the least toxic. The highest proportions of arsenite (As(III)), the presumably most toxic arsenic species, relative to total arsenic concentrations were found at drain sites. Our assessment of dissolved arsenic concentrations in various surface-water bodies in the Upper Klamath River Basin reveals geographical areas of consistently low (below 2.1 μg/L), moderate (below 10 μg/L) and high (above 10 μg/L) surface-water arsenic concentrations. South of Upper Klamath Lake, surface-water arsenic concentrations were consistently higher than 20 μg/L at two drain sites located in an area of predominant agricultural land use with extensive water re-use practices. North of Upper Klamath Lake, surface-water arsenic concentrations greater than 20 μg/L were consistently measured at sites with limited nearby agricultural activities, suggesting a geogenic source. The consistently high arsenic levels from the Wood River at Jackson F. Kimball State Park, Fort Creek, and Crooked Creek, which are sites located at or near headwater spring sources, suggest a natural background source of arsenic. Water flowing downstream from this area could be a potential source of arsenic to Upper Klamath Lake and the Upper Klamath River.

California, Oregon↗

USGS1976

Occurrence of arsenic in the Dry Creek Basin, Sonoma County, California

A reconnaissance study was made of occurrence of arsenic in the Dry Creek basin in northern California where the U.S. Army Corps of Engineers proposes to construct Warm Springs Dam. The purpose of the study, made from August through November 1974, was to determine the extent of any potential arsenic problems that may affect Lake Sonoma which would form behind the dam. Samples of sediment, water, and biota were collected and analyzed for arsenic content. Results of the study indicate that arsenic presents a potential problem only in the Little Warm Springs Creek area. Samples of the geothermal water from that area contained 140 micrograms of arsenic per litre of water--almost two and one-half times the maximum allowable concentration for drinking water. However, the contribution of arsenic to the proposed lake would be minimal because discharge of the geothermal water in the area is estimated to be only about 0.01 cubic foot per second (0.0003 cubic metre per second). Analyses of limited numbers of biota samples indicated that there is no biomagnification of arsenic through the food chain. Concentrations of arsenic in fish and benthic invertebrates collected from water containing high levels of arsenic were similar to concentrations in samples collected from water with low arsenic content. Concentrations of arsenic on sediment were low throughout the project area.

California↗

USGS1980

Chemical, physical, and radiological quality of selected public water supplies in Florida : January-May 1979

Verde Valley--an area of complex geology where the crust of the North American plate changes from unstable to stable--is in central Arizona in the transition zone between the Basin and Range and the Colorado Plateaus tectonic provinces. Volcanism and tectonism have been progressing northeastward along the transition zone for about 20 million years. The Verde Hot Springs area is the focal point of the intersection of three major lineaments. More than 100 water samples were collected from wells and springs in the valley, and temperatures of the potential geothermal resources were calculated using two geochemical methods or geothermometers--silica and Na-K-Ca geothermometers. Because of the high concentration of dissolved magnesium in the ground water, the silica geotemperatures are considered to be more reliable than the Na-K-Ca geotemperatures. The Camp Verde and Verde Hot Springs areas contain ground water that has quartz-silica geotemperatures of between 99 and 135C and chalcedony-silica geotemperatures of between 73 and 111C. The geochemical evidence to substantiate a geothermal resource in Verde Valley is not conclusive, and further work including test drilling, should be done to verify the silica geotemperatures given in the map. (Kosco-USGS)

Water-Resources Investigations Report↗

USGS1986

Potential for leakage among principal aquifers in the Memphis area, Tennessee

The principal aquifers in the Memphis area consist primarily of sand or sand and gravel, and the confining beds consist of clay, silt, sand, and lignite. The Jackson Formation and upper part of the Claiborne Group serve as the confining bed separating the water table aquifers from the Memphis Sand; the Flour Island Formation separates the Memphis Sand from the Fort Pillow Sand. Differences in total hydraulic head among the principal aquifers in the Memphis urban area result in vertical hydraulic gradients which create a potential for inter-aquifer exchange of water. Throughout this area, the gradient is downward from the water table aquifers to the Memphis Sand. In the central part of the Memphis urban area, the vertical hydraulic gradient is upward from the Fort Pillow Sand to the Memphis Sand, and in the eastern and western parts, it is downward from the Memphis Sand to the Fort Pillow Sand. The vertical distribution of carbon-14 data for water from the fluvial deposits, Memphis Sand, and Fort Pillow Sand shows an increase in the relative age of the water with depth. The areal distribution of carbon-14 data for water from the upper part of the Memphis Sand indicates that relatively recent water has been brought into the major cone of depression in the potentiometric surface of the Memphis Sand, either by horizontal movement or from downward vertical leakage. The normal, near-surface geothermal gradient in the Memphis area was determined to be 0.6 C/100 ft. Deviations from the normal geothermal gradient, in areas affected by intense pumping from the Memphis Sand, indicate that downward vertical leakage occurs from the water table aquifers through the Jackson-upper Claiborne confining bed to the Memphis Sand. The velocity of downward vertical leakage of water from the Memphis Sand through the Flour Island confining bed to the Fort Pillow Sand was determined to be 0.0066 ft/day by analysis of borehole temperature data from an observation well in the northeastern part of the Memphis area. From this velocity and the head difference between the Memphis Sand and the Fort Pillow Sand at this locality, the hydraulic conductivity of the Flour Island confining bed was determined to be 0.00114 ft/day. (Lantz-PTT)

Tennessee↗

USGS1987

Hydrologic and geochemical monitoring in Long Valley Caldera, Mono County, California, 1985

Hydrologic and geochemical monitoring, to detect changes caused by magmatic and tectonic processes in the Long Valley caldera has continued through 1985. The monitoring included the collection of the following types of data: chemical and isotopic composition of water and gases from springs, wells, and steam vents; temperatures in wells, springs, and steam vents; flow rates of springs and streams; water levels in wells; and barometric pressure and precipitation at several sites. In addition, reservoir temperatures for the geothermal system were estimated from computations based on chemical geothermometers applied to fluid samples from wells and springs. Estimates of thermal water discharged from springs were made on the basis of boron and chloride fluxes in surface waters for selected sites in the Casa Diablo area and along the Mammoth-Hot Creek drainage. These data are presented in tables and graphs. The Long Valley area was relatively quiescent throughout 1985 in terms of geodetic changes and seismic activity. As a consequence , the hydrologic system varied mainly in response to seasonal influences of temperature, atmospheric pressure, and precipitation. However, spring flows near Casa Diablo were influenced by pumping at the geothermal production well field nearby. (Author 's abstract)

Water-Resources Investigations Report↗

USGS2015

Metallogeny, exploitation and environmental impact of the Mt. Amiata mercury ore district (Southern Tuscany, Italy)

The Mt. Amiata mining district (Southern Tuscany, Italy) is a world class Hg district, with a cumulate production of more than 100,000 tonnes of Hg, mostly occurring between 1870 and 1980. The Hg mineralization at Mt. Amiata is younger than 0.3 Ma, and is directly related to shallow hydrothermal systems similar to present-day geothermal fields of the region. There is likely a continuum of Hg deposition to present day, because Hg emission from geothermal power plants is on-going. In this sense, the Mt. Amiata deposits present some analogies with “hot-spring type” deposits of western USA, although an ore deposit model for the district has not been established. Specifically, the source of Hg remains highly speculative. The mineralizing hydrothermal fluids are of low temperature, and of essentially meteoric origin. Recent results by our research group indicate that, 30 years after mine closure, the environmental effects of Hg contamination related to mining are still recorded by the ecosystem, namely on waterways of the Paglia and Tiber River basins. In particular, the close spatial connection between the town of Abbadia San Salvatore, the Hg mine within its immediate neighborhood, and the drainage catchment of the Paglia River has an influence also on Hg speciation, transported mainly in the particulate form by the river system. The extent of Hg contamination has been identified at least 100 km from Abbadia San Salvatore along the Paglia-Tiber River system. Estimated annual Hg mass loads transported by the Paglia River to the Tiber River were about 11 kg yr −1 . However, there is evidence that flood events may enhance Hg mobilization in the Paglia River basin, increasing Hg concentrations in stream sediment. The high methyl-Hg/Hg ratio in water in this area is an additional factor of great concern due to the potential harmful effects on human and wildlife health. Results of our studies indicate that the Mt. Amiata region is at present a source of Hg of remarkable environmental concern at the local, regional (Tiber River), and Mediterranean scales. Ongoing studies are aimed to a more detailed quantification of the Hg mass load input to the Mediterranean Sea, and to unravel the processes concerning Hg transport and fluid dynamics.

Tuscany↗

USGS1983

STABLE ISOTOPE GEOCHEMISTRY OF THERMAL FLUIDS FROM LASSEN VOLCANIC NATIONAL PARK, CALIFORNIA.

In the Lassen vapor-dominated geothermal system, surface manifestations of thermal fluids at high elevations (1800-2500 m) include superheated and drowned fumaroles, steam-heated acid-sulfate hot springs, and low-chloride bicarbonate springs. Neutral high-chloride hot water discharges at lower elevations. Deuterium and oxygen-18 data establish genetic connections between these fluids and with local meteoric waters. Steam from the highest temperature fumarole at Bumpass Hell and water from the highest chloride hot spring have isotopic compositions corresponding to vapor-liquid equilibrium at 235 degree C. Carbon and sulfur isotope data suggest that the CO//2 and H//2S in the system did not entirely originate from magmatic sources, but probably include contributions from thermal metamorphism of marine sedimentary rocks. Observations suggest that carbon and sulfur isotope variations are useful indicators of gas reactions and flow paths in geothermal systems. Refs.

Conference Paper↗

USGS1984

SEISMICITY OF THE LASSEN PEAK AREA, CALIFORNIA: 1981-1983.

Over 700 earthquakes occurred in the vicinity of Lassen Peak, California, from February 1981 through December 1983. These earthquakes define a broad, northwest-trending seismic zone that extends from the Sierra Nevada through the Lassen Peak area and either terminates or is offset to the northeast about 20 kilometers northwest of Lassen Peak. Approximately 25% of these earthquakes are associated with the geothermal system south of Lassen Peak. Earthquakes in the geothermal area generally occur at depths shallower than 6 kilometers.

Conference Paper↗

USGS1985

INDUCED SEISMICITY MECHANISM AT THE GEYSERS, CALIFORNIA.

Induced microearthquake activity at The Geysers geothermal reservoir is observed in the vicinity of eight geothermal steam power units. The earthquakes do not align with mapped faults but occur adjacent to steam wells. The sense of motion as deduced from focal mechanisms is strike-slip to reverse in the upper 1 km of the reservoir and changes to strike-slip to oblique normal slip at greater depth because of the increased lithostatic load. Below 1 km the reservoir is undergoing horizontal extension. Alignment of P and T axes with the regional stress field suggests that contraction of the reservoir contributes the incremental stress perturbation to the regional stress field and causes microearthquakes.

Conference Paper↗