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At least 991 records · Page 55Linked to original sources
USGS2014

The use of resistivity‐methods in the location of salt‐water bodies in the El Paso, Texas, Area

During 1935 and 1936 the Ground‐Water Division of the United States Geological Survey made an investigation of the ground‐water resources of the El Paso, Texas, Area. Geological and hydrological studies comprised the principal part of the investigation, and these studies were supplemented by measurements of earth‐resistivity made largely by the Geophysical Section of the Geological Survey along traverses aggregating 51 miles. The extent to which resistivity‐methods may be useful in ground‐water work has been the subject of much discussion. A full evaluation of the method can not be made at this time. However, the work in the El Paso Area indicates that the presence of faults and of underground bodies of salt water may be definitely determined by resistivity‐measurements.

Texas↗
USGS1977

Mineral resources of the Sheep Mountain Wilderness study area and the Cucamonga Wilderness and additions, Los Angeles and San Bernardino counties, California

A mineral survey of the Sheep Mountain Wilderness study area and Cucamonga Wilderness area and additions by the U.S. Geological Survey and Bureau of Mines in 1975 covered about 66,500 acres (26,500 ha) of the San Bernardino and Angeles National Forests in southern California. The two study areas are separated by San Antonio Canyon. The mineral resource potential was evaluated through geological, geochemical, and geophysical studies by the Geological Survey and through evaluation of mines and prospects by the Bureau of Mines.

California↗
USGS1993

The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology.

Journal of Geochemical Exploration↗
USGS2012

Scientific basis for safely shutting in the Macondo Well after the April 20, 2010 Deepwater Horizon blowout

As part of the government response to the Deepwater Horizon blowout, a Well Integrity Team evaluated the geologic hazards of shutting in the Macondo Well at the seafloor and determined the conditions under which it could safely be undertaken. Of particular concern was the possibility that, under the anticipated high shut-in pressures, oil could leak out of the well casing below the seafloor. Such a leak could lead to new geologic pathways for hydrocarbon release to the Gulf of Mexico. Evaluating this hazard required analyses of 2D and 3D seismic surveys, seafloor bathymetry, sediment properties, geophysical well logs, and drilling data to assess the geological, hydrological, and geomechanical conditions around the Macondo Well. After the well was successfully capped and shut in on July 15, 2010, a variety of monitoring activities were used to assess subsurface well integrity. These activities included acquisition of wellhead pressure data, marine multichannel seismic profiles, seafloor and water-column sonar surveys, and wellhead visual/acoustic monitoring. These data showed that the Macondo Well was not leaking after shut in, and therefore, it could remain safely shut until reservoir pressures were suppressed (killed) with heavy drilling mud and the well was sealed with cement.

Gulf of Mexico↗
USGS2024

Recent expansion of the Cascades Volcano Observatory geophysical network at Mount Rainier for improved volcano and lahar monitoring

The U.S. Geological Survey Cascades Volcano Observatory (CVO) recently expanded its continuous geophysical monitoring at Mount Rainier, an active stratovolcano in Washington state. CVO monitors volcanoes in Oregon, Washington, and Idaho to characterize volcanic systems and detect unrest. Mount Rainier has a history of large lahar occurrences in the Holocene, including at least one that may not have been associated with volcanic activity. Pierce County, Washington, is one of the areas most at risk from large lahars. In the 1990s, CVO collaborated with Pierce County to install the Rainier lahar detection system (RLDS), an automated system designed to detect large lahars in high‐risk drainages and mitigate hazards to heavily populated areas. The system was designed to detect lahars within 5–10 min of their occurrence and alert authorities of the need to evacuate populated low‐lying areas before lahar arrival. In addition, CVO and the Pacific Northwest Seismic Network (PNSN) maintained and expanded a network of seismic and geodetic monitoring stations on and near the edifice to provide adequate volcano monitoring capabilities. Since 2016, CVO has worked to upgrade the existing RLDS and to expand its capabilities into other drainages around Mount Rainier. This expansion includes installation of 25 new broadband seismic stations with many including infrasound along high‐risk drainages, as well as support for equipment upgrades at existing PNSN and CVO volcano monitoring sites. All stations transmit continuous, near‐real‐time data with dramatically improved spatial coverage for volcano monitoring and lahar hazard mitigation compared to the previous system.

Washington↗
USGS1949

Calculated gravity anomaly produced by possible fault under line 27-48

The seismograph data from Line 27-48 of Party 47 indicates the possibility of a high angle fault win a displacement of roughly 1,000 feet under South Barrow Test Well No. 2. This fault vas discussed in E. Wiancko's report for United Geophysical Company entitled "Report of Reflection Seismograph Survey in the Barrow Area During 1948". Mr. Delta. and Mr. English recently expressed a desire to know the magnitude of the calculated gravity anomaly produced by this probable fault. Their purpose was to determine the feasibility of proving and locating this fault, if exists, by several traverses with the gravimeter. As interpreted in Wiancko's report, the fault is nearly east-west in strike and is a reverse fault with the up-thrust block on the north side. The assumptions made for the calculation of the theoretical anomaly were that the density of the basement rock was 2.7, the density of the overlying rocks was 2.2 and the fault itself was taken directly from Plate I, Drawing No. 2044, of Wiancko's report, simplified, and reduced by a factor of 2. The calculated anomaly is shown in Fig. 1. A polar chart similar to the type described on pages 153-154 of Heiland's "Geophysical Exploration" was used in computing the value of the anomaly. It was assumed that the feature is two-dimensional. Broken lines indicate values of limited accuracy. It should be mentioned here that Mr. Roland Henderson and Mr. Isidore Zietz of the Section of Geophysics of the Geological Survey carried out the calculations and plotted Fig. 1.

Alaska↗
USGS1978

Geologic conditions in the Baltimore Canyon Trough area: A summary of U.S.G.S. second-year environment studies

Geologic studies of the outer Continental Shelf off the Middle Atlantic States (Baltimore Canyon Trough Area) have been carried out for two years to assess conditions and hazards which might cause or distribute oil spills and other potential pollution associated with petroleum exploration and development. These detailed investigations were requested and funded by the Bureau of Land Management to carry out its responsibility under the Outer Continental Shelf (OCS) Lands Act (67 Stat 462) of 1953 and the National Environmental Policy Act of 1969. Because of the energy crisis, these studies had to be mounted quickly so that a substantial body of data would be available for making decisions concerning environmental constraints on potential lease tracts. Indeed, pertinent data were available prior to Lease Sale #40 in the Middle Atlantic in August 1976. This was in part due to the alacrity of BLM's Environmental Division management, and in part due to the depth of USGS' experience in the area. For example, geophysical data and bottom samples had been collected since 1962 as part of the Geological Survey's role to "conduct geological and geophysical exploration in the Outer Continental Shelf" (43 U.S.C. 1340). At the advent of the energy crisis, the Atlantic-Gulf Coast Branch focused in-house resources and environmental assessment efforts on the Middle Atlantic OCS area. Thus, considerable information was available to guide the needed detailed studies.

Baltimore Canyon Trough area↗
USGS1991

Geophysical logs for selected wells in the Picher Field, northeast Oklahoma and southeast Kansas

The Roubidoux aquifer in northeastern Oklahoma is used extensively as a source of water for public supplies, commerce, industry, and rural water districts. The Roubidoux aquifer may be subject to contamination from abandoned lead and zinc mines of the Picher field. Water in flooded underground mines contains large concentrations of iron, zinc, cadmium, and lead. The contaminated water may migrate from the mines to the Roubidoux aquifer through abandoned water wells in the Picher field. In late 1984, the Oklahoma Water Resources Board began to locate abandoned wells that might be serving as conduits for the migration of contaminants from the abandoned mines. These wells were cleared of debris and plugged. A total of 66 wells had been located, cleared, and plugged by July 1985. In cooperation with the Oklahoma Water Resources Board, the U.S. Geological Survey took advantage of the opportunity to obtain geophysical data in the study area and provide the Oklahoma Water Resources Board with data that might be useful during the well-plugging operation. Geophysical logs obtained by the U.S. Geological Survey are presented in this report. The geophysical logs include hole diameter, normal, single-point resistance, fluid resistivity, natural-gamma, gamma-gamma, and neutron logs. Depths logged range from 145 to 1,344 feet.

Open-File Report↗
USGS1997

Hydrogeologic evaluation of the Upper Floridan aquifer in the southwestern Albany area, Georgia

A cooperative study by the Albany Water, Gas, and Light Commission and the U.S. Geological Survey was conducted to evaluate the hydrogeology of the Upper Floridan aquifer in an area southwest of Albany and west of the Flint River in Dougherty County, Ga. The study area lies in the Dougherty Plain district of the Coastal Plain physiographic province. In this area, the Upper Floridan aquifer is comprised of the upper Eocene Ocala Limestone, confined below by the middle Eocene Lisbon Formation, and semiconfined above by the undifferentiated Quaternary overburden. The overburden ranges in thickness from about 30 to 50 feet and consists of fine to coarse quartz sand, clayey sand, sandy clay, and clay. The Upper Floridan aquifer has been subdivided into an upper water-bearing zone and a lower water-bearing zone based on differences in lithology and yield. In the study area, the upper water-bearing zone generally consists of dense, highly weathered limestone of low permeability and ranges in thickness from 40 to 80 feet. The lower water-bearing zone consists of hard, slightly weathered limestone that exhibits a high degree of secondary permeability that has developed along fractures and joints, and ranges in thickness from about 60 to 80 feet. Borehole geophysical logs and borehole video surveys indicate two areas of high permeability in the lower water-bearing zone-one near the top and one near the base of the zone. A wellfield consisting of one production well and five observation-well clusters (one deep, intermediate, and shallow well in each cluster) was constructed for this study. Spinner flowmeter tests were conducted in the production well between the depths of 110 and 140 feet below land surface to determine the relative percentages of water contributed by selected vertical intervals of the lower water-bearing zone. Pumping rates during these tests were 1,080, 2,200, and 3,400 gallons per minute. The results of these pumping tests show that the interval between 118 and 124 feet below land surface contributes a significant percentage of the total yield to the well. An aquifer test was conducted by pumping the production well at a constant rate of 3,300 gallons per minute for about 49 hours. Time-dependent water-level data were collected throughout the pumping and recovery phases of the test in the pumped well and the observation wells. The maximum measured drawdown in the observation wells was about 2.6 ft. At about 0.5 mile from the pumped well, there was little measurable effect from pumping. Water levels increased during the test in wells located within about 3.75 miles of the Flint River (about 0.5 miles east of the pumping well). This water-level increase correlated with a 3.5-feet increase in the stage of the Flint River. The hydraulic characteristics of the Upper Floridan aquifer were evaluated using the Hantush-Jacob curve-matching and Jacob straight-line methods. Using the Hantush-Jacob method, values for transmissivity ranged from about 120,000 to 506,000 feet squared per day; values for storage coefficient ranged from 1.4 x 10-4 to 6.3 x 10-4; and values for vertical hydraulic conductivity of the overlying sediments ranged from 4.9 to 6.8 feet per day. Geometric averages for these values of transmissivity, storage coefficient, and vertical hydraulic conductivity were calculated to be 248,000 feet squared per day, 2.7 x 10-4, and 5.5 feet per day, respectively. If a dual porosity aquifer model (fracture flow plus matrix flow) is assumed instead of leakage, and the Jacob straight-line method is used with late time-drawdown data, the calculated transmissivity of the fractures ranged from about 233,000 to 466,000 feet squared per day; and storage coefficient of the fractures plus the matrix ranged from 5.1 x 10-4 to 2.9 x 10-2.

Georgia↗
USGS2011

Geophysical data collected from the St. Clair River between Michigan and Ontario, Canada (2008-016-FA)

In 2008, the U.S. Geological Survey (USGS), Woods Hole Coastal and Marine Science Center (WHCMSC), in cooperation with the U.S. Army Corps of Engineers conducted a geophysical and sampling survey of the riverbed of the Upper St. Clair River between Port Huron, Mich., and Sarnia, Ontario, Canada. The objectives were to define the Quaternary geologic framework of the riverbed of the St. Clair River to evaluate the relationship between morphologic change of the riverbed and underlying stratigraphy. This report presents the geophysical and sample data collected from the St. Clair River, May 29-June 6, 2008, as part of the International Upper Great Lakes Study, a 5-year project funded by the International Joint Commission of the United States and Canada to examine whether physical changes in the St. Clair River are affecting water levels within upper Great Lakes, to assess regulation plans for outflows from Lake Superior, and to examine the potential effect of climate change on the Great Lakes water levels (http://www.iugls.org). This document makes available the data that were used in a separate report, U.S. Geological Survey Open-File Report 2009-1137, which detailed the interpretations of the Quaternary geologic framework of the region. This report includes a description of the high-resolution acoustic and sediment-sampling systems that were used to map the morphology, surficial sediment distribution, and underlying geology of the Upper St. Clair River during USGS field activity 2008-016-FA (http://quashnet.er.usgs.gov/cgi-bin/datasource/public_ds_info.pl?fa=2008-016-FA). Video and photographs of the riverbed were also collected and are included in this data release. Future analyses will be focused on substrate erosion and its effects on river-channel morphology and geometry. Ultimately, the International Upper Great Lakes Study will attempt to determine where physical changes in the St. Clair River affect water flow and, subsequently, water levels in the Upper Great Lakes.

Open-File Report↗
USGS2002

Interpretation of borehole geophysical logs, aquifer-isolation tests, and water quality, supply wells 1 and 2, Willow Grove Naval Air Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania

Ground water pumped from supply wells 1 and 2 on the Willow Grove Naval Air Station/Joint Reserve Base (NAS/JRB) provides water for use at the base, including potable water for drinking. The supply wells have been contaminated by volatile organic compounds (VOC's), particularly trichloroethylene (TCE) and tetrachloroethylene (PCE), and the water is treated to remove the VOC's. The Willow Grove NAS/JRB and surrounding area are underlain by sedimentary rocks of the Triassic-age Stockton Formation, which form a complex, heterogeneous aquifer. The ground-water-flow system for the supply wells was characterized by use of borehole geophysical logs and heatpulse-flowmeter measurements. The heatpulse-flowmeter measurements showed upward and downward borehole flow under nonpumping conditions in both wells. The hydraulic and chemical properties of discrete water-bearing fractures in the supply wells were characterized by isolating each water-bearing fracture with straddle packers. Eight fractures in supply well 1 and five fractures in supply well 2 were selected for testing on the basis of the borehole geophysical logs and borehole television surveys. Water samples were collected from each isolated fracture and analyzed for VOC?s and inorganic constituents. Fractures at 50–59, 79–80, 196, 124–152, 182, 241, 256, and 350–354 ft btoc (feet below top of casing) were isolated in supply well 1. Specific capacities ranged from 0.26 to 5.7 (gal/min)/ft (gallons per minute per foot) of drawdown. The highest specific capacity was for the fracture isolated at 179.8–188 ft btoc. Specific capacity and depth of fracture were not related in either supply well. The highest concentrations of PCE were in water samples collected from fractures isolated at 236.8–245 and 249.8–258 ft btoc, which are hydraulically connected. The concentration of PCE generally increased with depth to a maximum of 39 mg/L (micrograms per liter) at a depth of 249.8? 258 ft btoc and then decreased to 21 mg/L at a depth of 345.3–389 ft btoc. Fractures at 68–74, 115, 162, 182, 205, and 314 ft btoc were isolated in supply well 2. Specific capacities ranged from 0.08 to less than 2.9 (gal/ min)/ft. The highest specific capacity was for the fracture isolated at 157–165.2 ft btoc. Concentrations of detected VOC's in water samples were 3.6 mg/L or less. Lithologic units penetrated by both supply wells were determined by correlating naturalgamma and single-point-resistance borehole geophysical logs. All lithologic units are not continuous water-bearing units because water-bearing fractures are not necessarily present in the same lithologic units in each well. Although the wells penetrate the same lithologic units, the lithologic location of only three water-bearing fractures are common to both wells. The same lithologic unit may have different hydraulic properties in each well. A regional ground-water divide is southeast of the supply wells. From this divide, ground water flows northwest toward Park Creek, a tributary to Little Neshaminy Creek. Potentiometric-surface maps were prepared from water levels measured in shallow and deep wells. For both depth intervals, the direction of ground-water flow is toward the northwest. For most well clusters, the vertical head gradient is downward from the shallow to the deeper part of the aquifer. Pumping of the supply wells at times can cause the vertical flow direction to reverse.

Water-Resources Investigations Report↗
USGS1982

Mineral resource potential map of the Hells Hole further planning area (RARE II), Greenlee County, Arizona, and Grant County, New Mexico

During 1979, the U.S. Geological Survey and the U.S. Bureau of Mines conducted field investigations to evaluate the mineral resource potential of the Hells Hole Further Planning Area. The investigations included geologic mapping, geophysical studies, geochemical sampling, and a survey of known mines, prospects, and mineralized areas. This report summarizes the results of those studies.

New Mexico, Arizona↗
USGS2014

Geophysical logging of bedrock wells for geothermal gradient characterization in New Hampshire, 2013

The U.S. Geological Survey, in cooperation with the New Hampshire Geological Survey, measured the fluid temperature of groundwater and other geophysical properties in 10 bedrock wells in the State of New Hampshire in order to characterize geothermal gradients in bedrock. The wells selected for the study were deep (five ranging from 375 to 900 feet and five deeper than 900 feet) and 6 had low water yields, which correspond to low groundwater flow from fractures. This combination of depth and low water yield reduced the potential for flow-induced temperature changes that would mask the natural geothermal gradient in the bedrock. All the wells included in this study are privately owned, and permission to use the wells was obtained from landowners before geophysical logs were acquired for this study. National Institute of Standards and Technology thermistor readings were used to adjust the factory calibrated geophysical log data. A geometric correction to the gradient measurements was also necessary due to borehole deviation from vertical. Maximum groundwater temperatures at the bottom of the logs ranged from 11.2 to 15.4 degrees Celsius. Geothermal gradients were generally higher than those typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 4 of the 10 wells studied but only obscured the part of the geothermal gradient signal where groundwater actually flowed into, out of, or through the well. Temperature gradients varied by mapped bedrock type but can also vary by localized differences in mineralogy or rock type within the wells.

New Hampshire↗
USGSDate not supplied

Integrated geophysical characterization of the Winthrop Landfill Southern Flow Path, Winthrop, Maine

The U.S. Geological Survey (USGS), in cooperation with United Technologies Corporation, used an integrated suite of borehole, surface, and water-borne geophysical methods near the site of the former Winthrop Landfill, Winthrop, Maine, to investigate the hydrogeology controlling the transport of leachate from the landfill to nearby Annabessacook Lake. During the fall of 2000 and summer of 2001, the USGS conducted borehole electromagnetic (EM) induction and gamma logging, and inductive terrain-conductivity, two-dimensional (2D) resistivity, continuous seismic reflection, and magnetic surveys. The objectives of this integrated geophysical study were to provide constraints on the location and extent of the southern flow path(s) of contamination from the landfill to the lake; identify shoreline seep geophysical signatures; identify potentially hidden seeps in the lake; and determine depth to bedrock below Annabessacook Lake in the study area. Interpretation of surface 2D resistivity, magnetic, and inductive terrain-conductivity data and borehole EM logs delineates an electrically conductive anomaly consistent with a leachate plume moving from the current landfill boundary southward through the overburden to the shores of Annabessacook Lake. Surface and borehole geophysical data collected south and southeast of the landfill indicate the presence of discrete, shallow conductive anomalies at the southeastern edge of the landfill and near the lakeshore. The conductive anomalies appear at increasing depths closer to the lake. Magnetic anomalies offshore confirm the presence of iron-rich landfill leachate discharging into the lake south of the landfill. High-resolution swept-frequency seismic data used to map sediment and grain size distribution in the lake sub-bottom along the shoreline identified sediment-infilled bedrock lows that may act as conduits for contaminant migration.

Maine↗
USGS2012

The problem of groundwater discharge into the seas

Introductory Note: The dynamic equilibrium of the various factors involved in the world water balance or budget is the central scientific problem of the International Hydrological Decade. One of the potentially vital elements of the balance is groundwater discharge to the oceans. To paraphrase the authors of the following Russian publication, the world water budget can't be properly balanced, statically or dynamically, until there are improved values for the amount of groundwater that is discharged directly to oceans, seas, and enclosed lakes. The following report, with its bibliography, presents some Russian approaches to the problem and provides a few bits of numerical information. The report was translated by Frank W. Trainer of the U.S. Geological Survey. The text has been slightly reduced in the interests of saving space but the bibliography is given in full and has been transcribed into more or less standard U.S. Geological Survey bibliographical style. ©1971. American Geophysical Union. All Rights Reserved.

Eos, Transactions, American Geophysical Union↗
USGS2000

Mount St. Helens - From the 1980 eruption to 2000

Mount St. Helens, Washington, is the most active volcano in the Cascade Range. Its most recent series of eruptions began in 1980 when a large landslide and powerful explosive eruption created a large crater, and ended 6 years later after more than a dozen extrusions of lava built a dome in the crater. Larger, longer lasting eruptions have occurred in the volcano's past and are likely to occur in the future. Although the volcano seems to have returned to a period of quiet, scientists with the U.S. Geological Survey and University of Washington Geophysics Program continue to closely monitor Mount St. Helens for signs of renewed activity.

Washington↗
USGS2000

Borehole-radar methods: Tools for characterization of fractured rock

Locating and characterizing bedrock fractures and lithologic changes is an important component of studies of ground water supply and contamination in fractured-rock aquifers. Borehole-radar reflection methods provide information on the location, orientation, and lateral extent of fracture zones that intersect the borehole, and can identify fractures in the rock surrounding the borehole that are not penetrated by drilling. Crosshole radar logging provides crosssectional maps of the electromagnetic properties of bedrock between boreholes that can identify fracture zones and lithologic changes and can also be used to monitor tracer tests. Borehole-radar logs can be integrated with results of surfacegeophysical surveys and other borehole-geophysical logs, such as acoustic or optical televiewer and flowmeter, to distinguish transmissive fractures from lithologic variations or closed fractures. Integrated interpretation procedures provide results that can be used to develop conceptual and numerical models, design monitoring and sampling programs, and monitor implementation of contamination remediation measures, such as blast-fracturing.

Fact Sheet↗
USGS2011

Bibliography of literature pertaining to Long Valley Caldera and associated volcanic fields

On May 25-27, 1980, Long Valley caldera was rocked by four M=6 earthquakes that heralded the onset of a wave of seismic activity within the caldera which has continued through the present. Unrest has taken the form of seismic swarms, uplift of the resurgent dome, and areas of vegetation killed by increased CO2 emissions, all interpreted as resulting from magma injection into different levels beneath the caldera, as well as beneath Mammoth Mountain along the southwest rim of the caldera. Continuing economic development in the Mammoth Lakes area has swelled the local population, increasing the risk to people and property if an eruption were to occur. The U.S. Geological Survey (USGS) has been monitoring geophysical activity in the Long Valley area since the mid-1970s and continues to track the unrest in real time with a sophisticated network of geophysical sensors. Hazards information obtained by this monitoring is provided to local, State, and Federal officials and to the public through the Long Valley Observatory. The Long Valley area also was scientifically important before the onset of current unrest. Lying at the eastern foot of the Sierra Nevada, the deposits from this active volcanic system have provided fertile ground for research into Neogene tectonics, Quaternary geology and geomorphology, regional stratigraphy, and volcanology. In the early 1970s, intensive studies of the area began through the USGS Geothermal Investigations Program, owing to the presence of a large young silicic volcanic system. The paroxysmal eruption of Long Valley caldera about 760,000 years ago produced the Bishop Tuff and associated Bishop ash. The Bishop Tuff is a well-preserved ignimbrite deposit that has continued to provide new and developing insights into the dynamics of ignimbrite-forming eruptions. Another extremely important aspect of the Bishop Tuff is that it is the oldest known normally magnetized unit of the Brunhes Chron. Thus, the age of the Bishop Tuff is used to define the beginning of the Brunhes Chron and helps constrain the Brunhes-Matuyama boundary. The Bishop ash, which was dispersed as far east as Nebraska, Kansas, and Texas, provides an important tephrostratigraphic marker throughout the Western United States. The obsidian domes of both the Mono and Inyo Craters, which were produced by rhyolitic eruptions in the past 40,000 years, have been well studied, including extensive scientific drilling through the domes. Exploratory drilling to 3-km depth on the resurgent dome and subsequent instrumentation of the Long Valley Exploratory Well (LVEW) have led to a number of important new insights. Scientific drilling also has been done within the Casa Diablo geothermal field, which, aside from drilling, has been commercially developed and is currently feeding 40 MW of power into the Southern California Edison grid. Studies in all the above-mentioned volcanic fields have contributed to the extensive scientific literature published on the Long Valley region. Although most of this scientific literature has been published since 1970, a significant amount of historical literature extends backward to the late 1800s. The purpose of this bibliography is to compile references pertaining to the Long Valley region from all time periods and all Earth science fields into a single listing, thus providing an easily accessible guide to the published literature for current and future researchers.

Open-File Report↗