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At least 1,801 records · Page 100Linked to original sources
USGS1957

Gravity prospecting for chromite deposits in Camaguey Province, Cuba

Detailed gravity surveys were made in Camaguey Province, Cuba, as part of a systematic exploration program conducted by the U. S. Geological Survey on behalf of the General Services Administration to locate deposits of refractory-grade chromite. During the period August 4, 1954, to April 5, 1956, a total of 41,921 gravity stations were established in nine areas embracing about 11.8 square miles in the Camaguey chromite district. The results of the surveys were used in connection with information obtained in geologic investigations to guide exploratory drilling.Gravimeters with low scale constants were used in making measurements sufficiently accurate to delimit anomalies as small as 0.5 gravity unit. The measurements were made over 20 X 40 and 30 X 60 meter grids and at stations 20 and 30 meters apart, respectively, along intermediate traverses in anomalous areas. Gravity differences were determined by single observations at individual stations, observing base stations hourly, and re-observing a few stations to check drift and accuracy of measurement. About 11 percent of the stations established had to be re-run because of errors in closure, microseisms, and instrument trouble.A large number of anomalies were found and evaluated according to geology, areal extent, and gravity relief. Depths to disturbing hypothetical bodies were computed to guide drilling. Test drilling of 106 positive anomalies revealed that ten features overlie deposits of chromite and 89 occur over bodies of other dense materials. The other seven anomalies were not explained by materials found in drilling. Core drilling on five of the chromite deposits revealed about 236,000 tons of chromite. An additional estimated 12,000 tons are contained in three deposits which were not blocked out. No estimate was made of the tonnage in two small deposits.

Camaguey↗
USGS1974

Detailed near-bottom geophysical profile across the continental slope off northern California

A geophysical profile was run across the continental slope off the California-Oregon border by use of a deeply submerged instrument package, approximately 50 m above the sea floor, containing a proton magnetometer and a 3.5-kHz transducer for shallow seismic penetration. Surface-towed seismic reflection equipment was operated concurrently. The deep-tow data show that the slope is relatively smooth; this agrees with interpretation of surface seismic profiles. Features smaller than 1 km in length can be resolved with the deep profiles but not with the surface profiles. The deep profiles show smallscale undulations less than 0.5 km long that are especially well formed on the steeper parts of the slope. These undulations may be caused by minor downslope movement of surface sediment or by depositional processes. The deep-tow and surface seismic profiles can be combined to give a more accurate structural picture of the continental slope than can be obtained with surface data alone.

California↗
USGS2018

Revised groundwater-flow model of the glacial aquifer system north of Aberdeen, South Dakota, through water year 2015

The city of Aberdeen, in northeastern South Dakota, requires an expanded and sustainable supply of water to meet current and future demands. Conceptual and numerical models of the glacial aquifer system in the area north of Aberdeen were developed by the U.S. Geological Survey in cooperation with the City of Aberdeen in 2012. The U.S. Geological Survey, in cooperation with the City of Aberdeen, completed a study to revise the original numerical groundwater-flow model using data through water year (WY) 2015 to aid the City of Aberdeen in their development of plans and strategies for a sustainable water supply and to increase understanding of the glacial aquifer system and groundwater-flow system near Aberdeen. The original model was revised to improve the fit between model-simulated values and observed (measured or estimated) data, provide greater insight into surface-water interactions, and improve the usefulness of the model for water-supply planning. The revised groundwater-flow model (hereafter referred to as the “revised model”) presented in this report supersedes the original model. The purpose of this report is to describe a revised groundwater-flow model including data collection, model calibration, and model results for the glacial aquifer system including the Elm, Middle James, and Deep James aquifers north of Aberdeen, South Dakota, using updated hydrologic data through WY 2015. The original numerical model was revised in several ways. The model was modified by adding four new layers, which included a surficial layer, two intervening confining layers, and a shale bedrock layer. The revised model provides an improved understanding of the groundwater-flow system in comparison to the original model. The principal aquifers of the model area include portions of the Elm, Middle James, and Deep James aquifers. The lithologic information used to define and describe the aquifers in the model area was unaltered; however, aquifer properties and boundary conditions were reviewed and updated using geological information reported by the South Dakota Department of Environmental and Natural Resources and information obtained from geophysical investigations for this study. The horizontal extent of the Elm, Middle James, and Deep James aquifers was unaltered from the original model. The thickness of the Deep James aquifer was modified based on interpretations from the geophysical investigations. In general, groundwater in the Elm aquifer flowed from northwest to southeast and locally towards rivers and streams. Similarly, in the Middle James and Deep James aquifers, groundwater also typically flowed southeast. The revisions made to the original model include use of the following MODFLOW stress packages: Recharge, Evapotranspiration, Time-Variant Specified Head, Wells, Drains, and Stream Flow Routing, all of which were updated from the original model except for the Stream Flow Routing Package, which replaced the River Package used in the original model. Model calibration is the process of estimating model parameters to minimize the differences, or residuals, between observed data and simulated values; therefore, Parameter ESTimation (PEST) software was used to optimize model input parameters by matching model-simulated values to observed data. Calibration parameters included horizontal hydraulic conductivity, vertical hydraulic conductivity, specific yield, specific storage, and vertical streambed conductance for stream and drain cells. Multipliers were used to calibrate the recharge and evapotranspiration stresses. Evapotranspiration extinction depth also was adjusted during model calibration. Comparisons to the original model are described to highlight the changes made in the revised model. In general, the revised model adequately simulates the natural system and compares favorably with observed hydrologic data. Simulated water levels were evaluated by comparing them to single water-level observations at selected well locations. The selected wells were the same wells used in the original model. The coefficient of determination value between simulated and observed water levels for the revised model was 0.89 and included simulated and observed values from October 1, 1974 (WY 1975), through September 30, 2015 (WY 2015). The coefficient of determination value for the original model was 0.94 and included simulated and observed values from October 1, 1974, through September 30, 2009. The difference may indicate that the original model could have been overfit to hydraulic head observations because base flow was not simulated. The additional data used in the revised model included some climatically wetter, more extreme periods, such as 2011, in which annual precipitation was 30.9 inches. Average annual precipitation for the original model timeframe, which included data from WYs 1975–2009, was 20.26 inches. Additional precipitation data for WYs 2010–15, included in the revised model timeframe, resulted in an average annual precipitation for WYs 1975–2015 in the model area of 20.6 inches. The larger variability in climate data coupled with the additional water-level data could explain the lower coefficient of determination for water levels in the revised model. The revised model was used to calculate various groundwater-budget components for steady-state and transient conditions for WYs 1975–2015. The time-variant specified-head cells in the revised model had the largest change when compared to the original steady-state model for inflows and outflows. Comparing the transient budget components between the original and the revised models indicated that inflow from recharge and time-variant specified-head cells had the greatest effect on groundwater inflows, and outflow from storage had the greatest effect on groundwater outflows. The simulated potentiometric contours from the revised model were compared with (1) the observed (interpreted) potentiometric surface (layer 2) and the hydraulic head values (layers 4 and 6) and (2) the simulated contours from the original model. The simulated hydraulic gradients and general direction of groundwater flow in the Elm aquifer in the revised model generally matched the observed potentiometric contours, the simulated potentiometric contours from the original model, and general flow directions interpreted to be perpendicular to the contours. Minor discrepancies between simulated potentiometric contours from the revised model and the observed potentiometric contours may be due to the lack of observed data in the model area. The revised model was designed to reduce the limitations of the original model. The revisions were validated by comparing the results of the original model with the revised model. A primary benefit of the revised model is the inclusion of the surficial deposits and the confining units as explicit layers in the model. The addition of the surficial layer was beneficial for three primary reasons: (1) more accurate representation of recharge from precipitation, (2) more accurate representation of groundwater evapotranspiration, and (3) more accurate representation of groundwater and surface-water interactions. The groundwater model is a numeric approximation of a complex physical hydrologic system, and the revised model data were interpolated in regions with sparse data. Additionally, model discretization included averaged and interpolated values for water use, withdrawal rates, and hydraulic conductivity. The revised model provides a useful estimate for hydraulic gradients, groundwater-flow directions, and aquifer response to groundwater withdrawals.

South Dakota↗
USGS2019

Geochemistry and geophysics of iron oxide-apatite deposits and associated waste piles with implications for potential rare earth element resources from ore and historic mine waste in the eastern Adirondack Highlands, New York, USA

The iron oxide-apatite (IOA) deposits of the eastern Adirondack Highlands, New York, are historical high-grade magnetite mines that contain variable concentrations of rare earth element (REE)-bearing apatite crystals. The majority of the deposits are hosted within sodically altered Lyon Mountain granite gneiss, although some deposits occur within paragneiss, gabbro, anorthosite, or potassically altered Lyon Mountain granite gneiss. The IOA deposits and the waste and/or tailings piles associated with them have potential as an unconventional resource for REEs. Reprocessing of these piles would have the advantage of partial recycling of the waste material to produce a set of critical elements. Thirty-four ore, nine rock, 25 waste-pile, and four tailings-pile samples were collected and analyzed for major, minor, and trace elements. At the tailings- and waste-pile sites, composite samples were collected by combining 30 to >50 subsamples randomly distributed over each pile. The total REE content of the waste and tailings piles varied from approximately 10 to 22,000 ppm, whereas the ore sample concentrations ranged from approximately 15 to 48,000 ppm total REEs. A positive correlation exists between the total REE content of ore and its associated waste pile. Median light REE/heavy REE values were 2.14 for waste/tailings piles and 2.25 for ore, which is a substantial relative enrichment in the heavy REEs in comparison to many developed REE mines, such as the mined carbonatites of Bayan Obo, China, and Mountain Pass, California. Importantly, the ore and waste samples are significantly enriched in both Y and Nd compared to other REEs in the samples. Other minor components such as Th are also elevated. Airborne radiometric surveys show large positive eTh and eU anomalies corresponding to tailings piles. Although it is a limited data set, geochemical data of unaltered and altered host rocks suggest a speculative new model for IOA ore formation in the Adirondack Highlands that is consistent with the geology and previously published data. The ferroan ore-hosting Lyon Mountain granite gneiss underwent localized potassic alteration that enriched the altered rock in Fe, REEs, Th, and other metals. A later sodic alteration event affected the previously potassically altered Lyon Mountain granite gneiss, which increased rock porosity and remobilized Fe, REEs, and other elements from the host rock into the iron ore seams. The sodic fluids responsible for ore formation were enriched in F and Cl.

New York↗
USGS2026

Color-Shaded Relief Bathymetry of Lake Chelan, Washington

In 2023, the U.S. Geological Survey (USGS) completed a 3-week field operation in Lake Chelan, Washington, the third deepest lake in the conterminous United States, to acquire sediment cores, high-resolution bathymetry data, and chirp sub-bottom profiles. The high-resolution bathymetry displayed in this map publication was collected using a Norbit Winghead i67-curved array multibeam system; raw data were cleaned and gridded (3 by 3 meters [m]) in the Teledyne CARIS software. In some locations where the slopes of Lake Chelan are near-vertical, multibeam returns were sparse, resulting in artifacts resembling holes that appear as grey dots within the color-shaded bathymetric relief. Although the 2023 bathymetric mapping of Lake Chelan resulted in similar morphometric characteristics to previous hydrographic campaigns (table 1; Kendra and Singleton, 1987; Pelletier and others, 1989), these new data provide a much more detailed understanding of the two physiographic basins that comprise Lake Chelan: the deeper (as deep as 445.8 m [fig. 1]; previously reported as 453 m) and narrower (1–2 kilometers [km] wide) Lucerne Basin to the north, and the shallower (as deep as 127.8 m [fig. 1]), and wider (2–3 km wide) Wapato Basin to the south. With this detailed imaging of Lake Chelan, we find pervasive morphological evidence of slope failure and mass-transport deposits (MTDs) in at least 89 locations within the lake and 63 subaqueous deltas (fig. 2). The deeper Lucerne Basin is dominated by steep slopes and numerous subaqueous deltas fed by steep fluvial catchments, whereas the Wapato Basin contains numerous landslide scarps, scars, and debris aprons along the more gently sloping lake margins, and abundant relict kettle structures from the Pleistocene deglaciation. Lake Chelan’s geomorphic, geophysical, and sediment data contain important records of glacial retreat and advance, regional volcanic eruptions, and earthquakes that generate ground motions severe enough to induce landslides recorded in the sediment as MTDs. The epicenter of the 1872 Washington State Earthquake (M 6.5–7.2; Bakun and others, 2002; Brocher and others, 2017; Sherrod and others, 2021) is along the Spencer Canyon Fault, near the southern end of Lake Chelan. Shaking from this earthquake was strong enough to affect local aquifers, induce liquefaction of unconsolidated sediments, produce large seiches (Brocher and others, 2018), and likely cause landslides within Lake Chelan.

Washington↗
USGS1960

The chief oxide-burgin area discoveries, East Tintic district, Utah; A case history

In 1955 exploration for base and precious metals was undertaken by Bear Creek Mining Company immediately north of the Main Tintic district , Utah . During the course of this work Bear Creek became interested in the East Tintic district , primarily as a result of the activities of the U.S. Geological Survey in that area . Data published on the East Tintic district by the Survey and others were studied and map data made available from various mining companies were compiled. Preliminary economic studies were made to determine the present day value of the type of ore body discovered previously in the district . Encouraging results from these investigations led to the selection of specific targets for exploration. Recommendations for a project program were made and approved. Negotiations were successfully concluded in mid-1956 for a unit lease agreement on lands in the East Tintic district owned by the Tintic Standard and Chief Consolidated mining companies and their subsidiaries. Of the targets selected for exploration, the Chief Oxide area seemed to be one of the most prominent. Our preliminary work in the Chief Oxide area corroborated the findings of the U.S. Geological Survey described in Part I of this paper. After careful consideration it was decided to gamble the cost of an exploration shaft in this area for the purpose of providing an underground drilling platform. We also hoped by means of underground workings to establish the existence and nature of the postulated fault. A limited amount of surface drilling was done prior to shaft sinking in order to locate a shaft site and also to obtain additional information of subvolcanic structure and alteration. Underground exploration in the Chief Oxide area was started in January, 1957. The Burgin shaft was sunk to a depth of 1,100 feet and by August, 1959, lateral development on the 1050 level totaled 4,721 feet and underground diamond drilling totaled 15,480 feet. Results of the work done to date are as follows: ( a ) Identification of the sedimentary rock section and an interpretation of the structure in the Burgin mine area . (b) Discovery by penetration of the previously postulated East Tintic thrust fault. (c) Discovery of large zones of manganese oxides and carbonates, which were found to be closely related to silver-lead-zinc mineralization. (d) Discovery of ore-grade lead-zinc mineralization within the footwall rocks of the East Tintic thrust. (e) Discovery of high-grade silver-lead ore within the thrust zone. Insofar as ore localization is concerned the most important structural feature in the Burgin mine area is the East Tintic thrust fault- a fact that opens up new ore potential over a large part of the East Tintic district not previously explored. Although the discoveries to date must be attributed essentially to the application of geology to exploration, the tools of geochemical prospecting and geophysics were also used, and the geochemical work, in particular, was found to be a definite aid in the selection of areas for further exploration.

Utah↗
USGS2000

Investigation of polyethylene passive diffusion samplers for sampling volatile organic compounds in ground water at Davis Global Communications, Sacramento, California, August 1998 to February 1999

Fourteen wells were instrumented with diffusion samplers as a test to determine whether the samplers could be used to obtain representative volatile organic compound concentrations at a study site in Sacramento, California. Single diffusion samplers were placed in 10-foot-long well screens, and multiple diffusion samplers were positioned in 20-foot-long well screens. Borehole geophysical logs and electromagnetic flowmeter tests were run in selected wells with 20-foot-long well screens prior to deploying the samplers. The diffusion samplers were recovered after 25 to 30 days, and the wells were then sampled by using the purge-and-sample method. In most wells, the concentrations obtained by using the downhole diffusion samplers closely matched those obtained by using the purge-and-sample method. In seven wells, the concentrations differed between the two methods by only 2 micrograms per liter (g/L) or less. In three wells, volatile organic compounds were not detected in water obtained by using either method. In the four remaining wells, differences between the methods were less than 2g/L in the 0.2- to 8.5-g/L concentration range and from 1.2 to 8.7g/L in the 10- to 26-g/L concentration range. Greater differences (23 percent or 14.5g/L, 31 percent or 66g/L, and 46 percent or 30g/L) between the two methods were observed for tetrachloroethene concentrations, which ranged between 30 and 211g/L in three wells. The most probable explanation for the differences is that in some wells, the purging induced drawdowns and introduced water that differed in volatile organic compound concentrations from the in situ water in contact with the screened interval of the well. Alternate explanations include the possibility of unrecorded changes in nearby contaminant-extraction-well operation during the equilibration period. The data suggest that the combined use of borehole flowmeter tests and diffusion samplers may be useful in optimizing the radius of capture of contaminated ground water by the contaminant-removal wells. Overall, the data suggest that the use of diffusion samplers provided an alternative sampling method to the purge-and-sample approach. 1U.S. Geological Survey, Stephenson Center, Suite 129, 720 Gracern Road, Columbia, South Carolina 29210-7651. 2U.S. Geological Survey, 6000 J Street, Sacramento, California 95819-6129.

Open-File Report↗
USGS1999

Cruise report for O1-99-SC Southern California Earthquake Hazards project

The focus of the Southern California Earthquake Hazards project is to identify the landslide and earthquake hazards and related ground-deformation processes occurring in the offshore areas that have significant potential to impact the inhabitants of the Southern California coastal region. The project activity is supported through the Coastal and Marine Geology Program of the Geologic Division of the U. S. Geological Survey (USGS) and is a component of the Geologic Division's Science Strategy under Goal 1—Conduct Geologic Hazard Assessments for Mitigation Planning (Bohlen et al., 1998). The project research is specifically stated under Activity 1.1.2 of the Science Strategy: Earthquake Hazard Assessments and Loss Reduction Products in Urban Regions. This activity involves "research, seismic and geodetic monitoring, field studies, geologic mapping, and analyses needed to provide seismic hazard assessments of major urban centers in earthquake-prone regions including adjoining coastal and offshore areas." The southern California urban areas, which form the most populated urban corridor along the U.S. Pacific margin, are among a few specifically designated for special emphasis under the Division's science strategy (Bohlen et al., 1998). The primary objective of the project is to help mitigate the earthquake hazards for the Southern California region by improving our understanding of how deformation is distributed (spatially and temporally) in the offshore with respect to the onshore region. To meet this objective, we are conducting field investigations to observe the distribution, character, and relative intensity of active (i.e., primarily Holocene) deformation within the basins and along the shelf adjacent to the most highly populated areas (Fig. 1). In addition, acoustic imaging should help determine the subsurface dimensions of the faults and identify the size and frequency of submarine landslides, both of which are necessary for evaluating the potential for generating destructive tsunamis in the southern California offshore. In order to evaluate the strain associated with the offshore structures, the initial results from the field mapping under this project will be used to identify possible sites for deployment of acoustic geodetic instruments to monitor strain in the offshore region. A major goal of mapping under this project is to provide detailed geologic and geophysical information in GIS data bases that build on the earlier studies and use the new data to precisely locate active faults and to map recent submarine landslide deposits.

California↗
USGS2024

Chemistry, growth, and fate of the unique, short-lived (2019–2020) water lake at the summit of Kīlauea Volcano, Hawaii

Less than a year after the 2018 Kīlauea caldera collapse and eruption, water appeared in newly deepened Halemaʻumaʻu crater. The lake—unprecedented in the written record—grew to a depth of ∼50 m before lava from the December 2020 eruption boiled it away. Surface water heightened concerns of potential phreatic or phreatomagmatic explosions but also offered a new means of possibly identifying eruption precursors. The U.S. Geological Survey Hawaiian Volcano Observatory (HVO) monitored the lake via direct visual observation, webcams, thermal imaging, colorimetry, and laser rangefinders. HVO also employed uncrewed aircraft systems to sample the water and measure near-lake gas composition. The lake's δD and δ 18 O indicate a groundwater source with substantial evaporation. The initial sample had a salinity (total dissolved solids concentration) of 71,000 mg/L and was rich in sulfate (∼53,000 mg/L), iron (∼500 mg/L), and magnesium (∼10,000 mg/L). Subsequent samples were slightly more dilute. The water's pH (∼4), δ 34 S (+4.3‰), and surface temperatures (up to 85°C) suggest, rather than significant scrubbing of magmatic volatiles, leaching of basalt and reactions with sulfate minerals resulted in high concentrations of sulfate and other solutes. Thermodynamic modeling and precipitate mineralogy indicate that water composition was controlled by iron oxidation and sulfate dissolution. Although the lake exhibited no detectable precursors before the next eruption, and phreatic or phreatomagmatic explosions did not materialize, our multi-parameter approach to monitoring yielded an enhanced understanding of the hydrologic, geologic, and magmatic conditions that led to the formation of the unique and short-lived lake.

Hawaii↗
USGS2011

A promising tool for subsurface permafrost mapping-An application of airborne geophysics from the Yukon River Basin, Alaska

Permafrost is a predominant physical feature of the Earth's Arctic and Subarctic clines and a major consideration encompassing ecosystem structure to infrastructure engineering and placement. Perennially frozen ground is estimated to cover about 85 percent of the state of Alaska where northern reaches are underlain with continuous permafrost and parts of interior Alaska are underlain by areas of discontinuous and (or) sporadic permafrost (fig. 1). The region of Interior Alaska, where permafrost is scattered among unfrozen ground, is a complex mosaic of terrains and habitats. Such diversity creates arrays of lakes and surface-water and groundwater patterns that continental populations of migratory waterfowl and internationally significant fisheries have adapted to over time. A road or pipeline might pass over frozen and unfrozen ground, affecting the types of materials and engineering approaches needed to sustain the infrastructure. Effective mapping of discontinuous permafrost at scales meaningful ecologically and (or) from an engineering perspective has been a long-standing challenge. Using techniques such as borehole logging for site-specific assessments or botanical techniques that can suggest underlying permafrost distributions can be labor intensive and difficult to accomplish at the scale and remoteness of much of Alaska. The climate is changing in the Arctic and Subarctic regions. The warming observed throughout much of Alaska could create widespread changes in permafrost. How the warming of the permafrost affects near-surface processes, ecosystems, and community infrastructure and ecosystems is not clear. A better understanding of the dynamic distribution and physical properties of permafrost, from continuous to discontinuous, will provide knowledge of how the permafrost environment may change in the future and help inform engineering and natural resource response strategies. Here we discuss an application of an airborne remote sensing methodology for mapping and shade imaging permafrost characteristics at various scales. This work provides the first look into three-dimensional distribution of permafrost in the areas around Fort Yukon and is a demonstration of the application of airborne electromagnetic (AEM) to permafrost mapping. Such an approach is attractive, particularly in Arctic and Subarctic studies, where ground access is difficult and ecosystems are fragile. In June 2010, the U.S. Geological Survey (USGS) conducted an AEM survey near Fort Yukon, Alaska. The primary focus of this survey was to map the distribution of permafrost in selected areas in order to supply information for the development of groundwater models of the Yukon River Basin. However, the methodologies have more far-reaching ecological and engineering applications. Approximately 1,800 line kilometers were acquired in a combination of typical block style surveying in the immediate area of Fort Yukon and in long reconnaissance lines over a broader area. The widely spaced lines were flown to cross the modern Yukon River in "X" like patterns with intersections at features that have been previously studied (fig. 2). AEM is used to gather data on the electrical resistivity of materials in the subsurface below the flight path of the helicopter, which are then analyzed to interpret the subsurface lithology and the location and extent of permafrost. For this survey, the electrical resistivity was imaged to depths on the order of 50-100 meters. Images from the survey can be qualitatively compared with known permafrost features and suggest new permafrost features. Electrical properties of earth materials are affected by lithology as well as temperature and the presence of ice; frozen materials become substantially more resistive. This allows for the identification of permafrost from the resistivity image (Abraham and others, 2011). In the area of Fort Yukon, the AEM survey shows elevated resistivities extending to depth, likely indicative of thick permafrost. This depth corresponds well to observations from a borehole drilled in the area in the late 1990s, which detected permafrost to a depth of about 100 meters (Clark and others, 2009). In contrast to the area of Fort Yukon, the Yukon River and its floodplain are not associated with deep resistive sediments, suggesting a lack of deep permafrost, at least within the depth range of the AEM mapping (fig. 3).

Yukon River Basin↗
USGS2012

The velocity field along the San Andreas Fault in central and southern California

The velocity field within a 100‐km‐broad zone centered on the San Andreas fault between the Mexican border and San Francisco Bay has been inferred from repeated surveys of trilateration networks in the 1973–1989 interval. The velocity field has the appearance of a shear flow that remains parallel to the local strike of the fault even through such major deflections as the big bend of the San Andreas fault in the Transverse Ranges of southern California. Across‐strike profiles of the fault‐parallel component of velocity exhibit the expected sigmoidal shape, whereas across‐strike profiles of the fault‐normal component of velocity are flat and featureless. No significant convergence upon the fault is observed even along the big bend sector of the fault. Simple dislocation models can explain most of the features of the observed velocity field, but those explanations are not unique. About 35 mm/yr of relative plate motion is accounted for within the span of the trilateration networks. Geologic studies indicate that the secular slip rate on the San Andreas fault is about 35 mm/yr. The agreement between these two estimates implies that most of the strain accumulation is elastic and will be recovered in subsequent earthquakes. The relative motion observed across the San Andreas fault (35 mm/yr) plus that observed across the Eastern California shear zone (8 mm/yr) accounts for most (43 mm/yr) of the observed North America‐Pacific relative plate motion (47 mm/yr).

California↗
USGS1956

Regional gravity survey in northeastern Oklahoma and southeastern Kansas

In 1948 the U. S. Geological Survey, in cooperation with the U. S. Coast and Geodetic Survey, made a regional gravity survey in northeastern Oklahoma and southeastern Kansas in connection with the studies of the deflection of the vertical. About 550 gravity stations were occupied with spacings of 5 to 10 miles in parts of 54 counties, and a Bouguer anomaly map, contoured at intervals of 5 milligals, was drawn. In southeastern Kansas there is a lack of correlation of regional gravity with known regional structural geology. The observed gravity anomalies are apparently caused principally by variations of density in the Precambrian basement and indicate a basement of complex nature, made up of rocks of contrasting properties, with a regional grain striking predominantly west or west-northwest. In northeastern Oklahoma the several observed regional gravity anomalies indicate different degrees of correlation of regional gravity with regional structural geology. In the Precambrian highland area in Osage, Pawnee, and Creek Counties, there is a lack of correlation, as the gravity anomaly is probably caused chiefly by density contrasts within the basement complex. The anomaly associated with the Hunton arch is probably caused partly by structural relief of the rocks of pre-Pennsylvanian age and partly by density contrasts within the basement, and thus indicates some correlation. The steep gravity gradients along the outer flanks of the Ozark uplift indicate good correlation with the subsurface geology. The great anomaly over the Arkansas basin, which indicates a close correlation, is probably caused largely--but perhaps not entirely--by downwarping of the basement and pre-Pennsylvanian rocks.

Missouri, Kansas, Oklahoma↗
USGS2021

Geologic and geophysical maps of the Newfoundland Mountains and part of the adjacent Wells 30' x 60' quadrangles, Box Elder County, Utah

The Newfoundland Mountains map area (Newfoundland Mountains and adjacent part of Wells 30' x 60' quadrangles) is located in Box Elder County, northwestern Utah. The map encompasses broad expanses of the Great Salt Lake Desert as well as several picturesque mountain ranges (figures 1, 2, and 3). The geology of the area was last mapped and summarized by Doelling (1980). Since that landmark study, much of the area has been mapped in greater detail and new paleontologic, geochronologic, and structural data provide for an updated view of the geology. In addition, new geophysical studies (Langenheim and others, 2013; Langenheim, 2016) provide key data for improved interpretation of subsurface geology. The geologic map (plate 1) was compiled from fifteen 7.5' quadrangles mapped at a scale of 1:24,000 (mostly in the western part of the area), one map covering the Newfoundland Mountains at a scale of 1:31,680 (Allmendinger and Jordan, 1989), unpublished geologic mapping at scales from 1:24,000 to 1:50,000 (most by Miller; Bovine Mountain by T.E. Jordan), and reconnaissance mapping and aerial photo interpretation in intervening areas by Miller. Some published maps were remapped or reinterpreted by the authors in light of more recent studies north of the map area. Geologic mapping conducted as part of several theses/dissertations and a few published papers also were used (plate 2, index to geologic mapping). Concealed faults under valley bottoms were interpreted from gravity and aeromagnetic data. Our approach for this map was to integrate across the main themes of the mapped geology by generalizing units, structures, and polygons. This has the aim of illustrating the principal tectonic and stratigraphic packages, as well as illustrating the patterns of surficial units and geomorphology. Cross sections (plate 2) were constructed to coincide with representative cross sections for several detailed geologic maps. This approach required large bends across valleys. Basin geometry shown in the cross sections was constrained by gravity data and a seismic line since few deep drill holes are available.

Utah↗
USGS2018

Lava lake activity at the summit of Kīlauea Volcano in 2016

The ongoing summit eruption at Kīlauea Volcano, Hawai‘i, began in March 2008 with the formation of the Overlook crater, within Halema‘uma‘u Crater. As of late 2016, the Overlook crater contained a large, persistently active lava lake (250 × 190 meters). The accessibility of the lake allows frequent direct observations, and a robust geophysical monitoring network closely tracks subtle changes at the summit. These conditions present one of the best opportunities worldwide for understanding persistent lava lake behavior and the geophysical signals associated with open-vent basaltic eruptions. In this report, we provide a descriptive and visual summary of lava lake activity during 2016, a year consisting of continuous lava lake activity. The lake surface was composed of large black crustal plates separated by narrow incandescent spreading zones. The dominant motion of the surface was normally from north to south, but spattering produced transient disruptions to this steady motion. Spattering in the lake was common, consisting of one or more sites on the lake margin. The Overlook crater was continuously modified by the deposition of spatter (often as a thin veneer) on the crater walls, with frequent collapses of this adhered lava into the lake. Larger collapses, involving lithic material from the crater walls, triggered several small explosive events that deposited bombs and lapilli around the Halema‘uma‘u Crater rim, but these did not threaten public areas. The lava lake level varied over several tens of meters, controlled primarily by changes in summit magma reservoir pressure (in part driven by magma supply rates) and secondarily by fluctuations in spattering and gas release from the lake (commonly involving gas pistoning). The lake emitted a persistent gas plume, normally averaging 1,000–8,000 metric tons per day (t/d) of sulfur dioxide (SO 2 ), as well as a constant fallout of small juvenile and lithic particles, including Pele’s hair and tears. The gas emissions created volcanic air pollution (vog) that affected large areas of the Island of Hawai‘i. The summit eruption has been a major attraction for visitors in Hawai‘i Volcanoes National Park. During 2016, the rising lake levels allowed the lake and its spattering to be more consistently visible from public viewing areas, enhancing the visitor experience. The U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) closely monitors the summit eruption and keeps emergency managers and the public informed of activity.

Hawai'i↗
USGS2014

Brine contamination to aquatic resources from oil and gas development in the Williston Basin, United States

The Williston Basin, which includes parts of Montana, North Dakota, and South Dakota in the United States and the provinces of Manitoba and Saskatchewan in Canada, has been a leading domestic oil and gas producing region for more than one-half a century. Currently, there are renewed efforts to develop oil and gas resources from deep geologic formations, spurred by advances in recovery technologies and economic incentives associated with the price of oil. Domestic oil and gas production has many economic benefits and provides a means for the United States to fulfill a part of domestic energy demands; however, environmental hazards can be associated with this type of energy production in the Williston Basin, particularly to aquatic resources (surface water and shallow groundwater) by extremely saline water, or brine, which is produced with oil and gas. The primary source of concern is the migration of brine from buried reserve pits that were used to store produced water during recovery operations; however, there also are considerable risks of brine release from pipeline failures, poor infrastructure construction, and flow-back water from hydraulic fracturing associated with modern oilfield operations. During 2008, a multidisciplinary (biology, geology, water) team of U.S. Geological Survey researchers was assembled to investigate potential energy production effects in the Williston Basin. Researchers from the U.S. Geological Survey participated in field tours and met with representatives from county, State, tribal, and Federal agencies to identify information needs and focus research objectives. Common questions from agency personnel, especially those from the U.S. Fish and Wildlife Service, were “are the brine plumes (plumes of brine-contaminated groundwater) from abandoned oil wells affecting wetlands on Waterfowl Production Areas and National Wildlife Refuges?” and “are newer wells related to Bakken and Three Forks development different than the older, abandoned wells (in terms of potential for affecting aquatic resources)?” Of special concern were the wetland habitats of the ecologically important Prairie Pothole Region, which overlays a part of the Williston Basin and is recognized for the production of a majority of North America’s migratory waterfowl. On the basis of the concerns raised by on-the-ground land managers, as well as findings from previous research, a comprehensive study was developed with the following goals: summarize existing information pertaining to oil and gas production and aquatic resources in the Williston Basin; assess brine plume migration from new and previously studied sites in the Prairie Pothole Region; perform a regional, spatial evaluation of oil and gas production activities and aquatic resources; assess the potential for brine contamination to wetlands and streams; and hold a decision analysis workshop with key stakeholders to discuss issues pertaining to oil and gas production and environmental effects and to identify information gaps and research needs. This report represents an initial, multidisciplinary evaluation of measured and potential environmental effects associated with oil and gas production in the Williston Basin and Prairie Pothole Region. Throughout this report there are reviews of current knowledge, and discussions relating to data gaps and research needs. On the basis of the information presented, future research needs include: regional geophysical and water-quality assessments to establish baselines for current conditions and estimate the extent of previous brine contamination, investigations into the direct effects of brine to biotic communities, and evaluations to identify the most effective techniques to mitigate brine contamination.

Montana, North Dakota↗
USGS2016

San Pedro River Aquifer Binational Report

The United States and Mexico share waters in a number of hydrological basins and aquifers that cross the international boundary. Both countries recognize that, in a region of scarce water resources and expanding populations, a greater scientific understanding of these aquifer systems would be beneficial. In light of this, the Mexican and U.S. Principal Engineers of the International Boundary and Water Commission (IBWC) signed the “Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program" on August 19, 2009 (IBWC-CILA, 2009). This IBWC “Joint Report” serves as the framework for U.S.-Mexico coordination and dialogue to implement transboundary aquifer studies. The document clarifies several details about the program such as background, roles, responsibilities, funding, relevance of the international water treaties, and the use of information collected or compiled as part of the program. In the document, it was agreed by the parties involved, which included the IBWC, the Mexican National Water Commission (CONAGUA), the U.S. Geological Survey (USGS), and the Universities of Arizona and Sonora, to study two priority binational aquifers, one in the San Pedro River basin and the other in the Santa Cruz River basin. This report focuses on the Binational San Pedro Basin (BSPB). Reasons for the focus on and interest in this aquifer include the fact that it is shared by the two countries, that the San Pedro River has an elevated ecological value because of the riparian ecosystem that it sustains, and that water resources are needed to sustain the river, existing communities, and continued development. This study describes the aquifer’s characteristics in its binational context; however, most of the scientific work has been undertaken for many years by each country without full knowledge of the conditions on the other side of the border. The general objective of this study is to use new and existing research to define the general hydrologic framework of the Binational San Pedro Aquifer (BSPA), to gather hydrogeological and other relevant data in preparation for future work such as an updated groundwater conceptual model and budget and to establish the basis for a binational numerical model. The specific objectives are as follows: Understand the current state of knowledge with respect to climate, geology, soils, land cover, land use, and hydrology of the aquifer in its binational context; Compile and create a database of scientific information from both countries; Identify data gaps and identify what data would be necessary to update, in a subsequent phase, the hydrologic model of the aquifer system, including surface- and groundwater interactions on a binational level. The BSPB is one of the most studied basins in the region, and a database of publications has been compiled as part of this project. Previous studies include topics that range from geophysics and hydrogeology to biology and ecosystem services. The economic drivers on each side of the border are quite different. In the Arizona 4 portion of the basin military and tourism dominate while in the Sonoran portion, mining is the most important industry. Water management is also different in the two countries. In Mexico, primary authority for management of water resources devolves from the federal government. In the United States, primary authority rests with the states except in cases of interstate surface waters. Binational waters are not currently jointly managed by the two countries except in cases where treaties have been negotiated such as for the Rio Grande and Colorado Rivers. Thus, there is currently no binational coordination or treaty governing the management of groundwater.

Report↗
USGS1999

Digital mapping of the Mars Pathfinder landing site: Design, acquisition, and derivation of cartographic products for science applications

The Imager for Mars Pathfinder (IMP) acquired more than 16,000 images and provided panoramic views of the surface of Mars at the Mars Pathfinder landing site in Ares Vallis. This paper describes the stereoscopic, multispectral IMP imaging sequences and focuses on their use for digital mapping of the landing site and for deriving cartographic products to support science applications of these data. Two‐dimensional cartographic processing of IMP data, as performed via techniques and specialized software developed for ISIS (the U.S. Geological Survey image processing software package), is emphasized. Cartographic processing of IMP data includes ingestion, radiometric correction, establishment of geometric control, coregistration of multiple bands, reprojection, and mosaicking. Photogrammetric processing, an integral part of this cartographic work which utilizes the three‐dimensional character of the IMP data, supplements standard processing with geometric control and topographic information [ Kirk et al. , this issue]. Both cartographic and photogrammetric processing are required for producing seamless image mosaics and for coregistering the multispectral IMP data. Final, controlled IMP cartographic products include spectral cubes, panoramic (360° azimuthal coverage) and planimetric (top view) maps, and topographic data, to be archived on four CD‐ROM volumes. Uncontrolled and semicontrolled versions of these products were used to support geologic characterization of the landing site during the nominal and extended missions. Controlled products have allowed determination of the topography of the landing site and environs out to ∼60 m, and these data have been used to unravel the history of large‐ and small‐scale geologic processes which shaped the observed landing site. We conclude by summarizing several lessons learned from cartographic processing of IMP data.

Journal of Geophysical Research E: Planets↗
USGS2020

Geological and thermal control of the hydrothermal system in northern Yellowstone Lake: Inferences from high resolution magnetic surveys

A multiscale magnetic survey of the northern basin of Yellowstone Lake was undertaken in 2016 as part of the Hydrothermal Dynamics of Yellowstone Lake Project (HD‐YLAKE)—a broad research effort to characterize the cause‐and‐effect relationships between geologic and environmental processes and hydrothermal activity on the lake floor. The magnetic survey includes lake surface, regional aeromagnetic, and near‐bottom autonomous underwater vehicle (AUV) data. The study reveals a strong contrast between the northeastern lake basin, characterized by a regional magnetic low punctuated by stronger local magnetic lows, many of which host hydrothermal vent activity, and the northwestern lake basin with higher‐amplitude magnetic anomalies and no obvious hydrothermal activity or punctuated magnetic lows. The boundary between these two regions is marked by a steep gradient in heat flow and magnetic values, likely reflecting a significant structure within the currently active ~20‐km‐long Eagle Bay‐Lake Hotel fault zone that may be related to the ~2.08‐Ma Huckleberry Ridge caldera rim. Modeling suggests that the broad northeastern magnetic low reflects both a shallower Curie isotherm and widespread hydrothermal activity that has demagnetized the rock. Along the western lake shoreline are sinuous‐shaped, high‐amplitude magnetic anomaly highs, interpreted as lava flow fronts of upper units of the West Thumb rhyolite. The AUV magnetic survey shows decreased magnetization at the periphery of the active Deep Hole hydrothermal vent. We postulate that lower magnetization in the outer zone results from enhanced hydrothermal alteration of rhyolite by hydrothermal condensates while the vapor‐dominated center of the vent is less altered.

Wyoming↗

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