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The volcanic islands making up the Azores Archipelago rise above sea from a prominent submarine topographic high (the “Azores Plateau”), marked by the 2000-m bathymetric contour. Specifically, the Azores Islands lie at the so-called “Azores Triple Junction” (ATJ), where the Eurasian, North American, and African (or Nubian) tectonic plates meet. In general terms, the ATJ is defined by the Mid-Atlantic Ridge (MAR) separating the North American plate from the other two, and the Azores–Gibraltar fault zone separating the Eurasian and African plates. In addition, the existence of a mantle plume (“hotspot) beneath Azores Plateau has been inferred in many previous investigations. Not surprisingly, because of its distinctive...
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Ultrasonic and endoscopic examination of Missouri River sturgeons has been shown effective for sex and reproductive stage determination (Wildhaber et al., 2005; Bryan et al., in press; Wildhaber et al., in press). In the application of both methodologies, sturgeon are inverted and submerged in water (Fig. 1 and 2). Sturgeon are docile enough in the inverted position that anesthesiology is not needed. During ultrasonic examination the entire body cavity is scanned using the probe (Fig. 1). During endoscopic examination, the vent area is positioned out of the water and the probe is inserted into the gonoduct (Fig. 2). The gonoduct is similar in both sexes, starting from the urogenital pore it forks into two long...
Categories: Publication; Types: Citation
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Ground water provides much of the water supply for residents of Tooele Valley (fig. 1). The protection, development, and wise management of ground-water resources are important to support community growth and to ensure the continued availability of ground water for all users.The U.S. Geological Survey, in cooperation with Tooele County, Tooele City, Grantsville City, the U.S. Army, and the State of Utah, has been studying the water resources of Tooele Valley since 1913 to define the quality and amount of water in the principal ground-water aquifers. The most recent studies in the 1990s have provided new insights into the hydrology of the valley. This fact sheet presents a synopsis of the recent studies and describes...
Categories: Publication; Types: Citation; Tags: Fact Sheet
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Ground water is an important freshwater source for domestic and livestock uses in southeastern Utah because of the arid climate and unavailability of surface water from the San Juan River. The study area includes about 1,200 square miles in the southeastern corner of Utah (fig. 1). Precipitation on mountainous areas north, south, and east of the study area (fig. 2) seeps into the Navajo and overlying aquifers where the sandstones that contain the aquifers are exposed at the surface along mountain flanks. The ground water then moves slowly away from the mountainous areas toward the area of lowest elevation 109°30' in the region, the San Juan River. The ground water reappears at land surface where it discharges as...
Categories: Publication; Types: Citation; Tags: Fact Sheet
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The southwestern region of the United States is a land of extremes and contrasts. Elevations vary from below sea level in the Imperial Valley of California to mountain peaks approaching 4,000 meters. Landscapes are striking and variable and include mountains, foothills, canyons, deserts, plains, and rivers. The area is arid or semiarid and, depending on the location, may have mild winters and summers, periods of bitter cold, or intervals of intense heat. Climate is inextricably tied to water and its availability. Historically, water varied from abundant to sparse over the span of a year, and adaptations of native plants and animals reflect those extremes. Annual precipitation, usually in the form of rain, varies...
Categories: Publication; Types: Citation
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This summary of Hawaiian lacustrine limnology is based on 12 years of field and literature surveys of archipelagic inland waters. Lakes here are distinguished from other standing waters by limits on surface oceanic area (> 0.1 ha) and depth (> 2 m), and by the absence of flatural surface oceanic connection. A variety of extinct and existing water bodies, sometimes referred to as lakes, are noted. Six lakes are described. Five of them are in crater basins, 3 are freshwater, and 2 are elevated (highest = 3969 m). The scarcity of elevated lakes results from general permeability of the substrata. Among the 6 lakes, surface areas range from 0.22 to 88 ha and maximum depths from 3 to 248 m. Naturally occurring aquatic...
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This release provides the data for a comprehensive survey of geologic structures in the eastern Española Basin of the Rio Grande rift, New Mexico. The release includes data and analyses from 53 individual fault zones and 22 other brittle structures, such as breccia zones, joints, and veins, investigated at a total of just over 100 sites. Structures were examined and compared from poorly lithified Tertiary sediments, as well as Paleozoic sedimentary and Proterozoic crystalline rocks. Data and analyses, include geologic maps; field observations and measurements; orientation, kinematic paleostress analyses and modeling; statistical examination of 575 fault trace lengths derived from aeromagnetic data in the Española...
Categories: Publication; Types: Citation
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We report on the development of a No-project alternative analysis (NPAA) or “business as usual” scenario with respect to a 20-year projection of 21 indicators of environmental and socioeconomic conditions in the Lake Tahoe Basin for the Tahoe Regional Planning Agency (TRPA). Our effort was inspired by earlier work that investigated the tradeoffs between an environmental and an economic objective. The NPAA study has implications for a longer term goal of building a Tahoe Decision Support System (TDSS) to assist the TRPA and other Basin agencies in assessing the outcomes of management strategies. The NPAA assumes no major deviations from current management practices or from recent environmental or societal trends...
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Water-quality data for discharges from 140 abandoned mines in the Bituminous and Anthracite Coalfields of Pennsylvania illustrate relations among pH, sulfate, and dissolved metal concentrations. The pH for the 140 samples ranged from 2.7 to 7.3, with two modes at pH 2.5 to 4 (acidic) and 6 to 7 (near neutral). Generally, flow rates were smaller and solute concentrations were greater for low-pH samples; flow rates increased with pH. Although the pH distribution was similar for the bituminous and anthracite subsets, the bituminous discharges had smaller median flow rates, greater concentrations of sulfate, iron, and aluminum, and smaller concentrations of barium and lead than anthracite discharges with the same pH...
Categories: Publication; Types: Citation
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This report is the first in a series of three reports that provide information about high-frequency (HF) nutrient and biogeochemical monitoring in the Sacramento–San Joaquin Delta of northern California (Delta). This first report provides an introduction to the reasons for and fundamental concepts behind collecting HF measurements, and describes the benefits associated with a real-time, continuous, HF, multi-parameter water quality monitoring station network that is co-located with flow stations. It then provides examples of how HF nutrient measurements have improved our understating of nutrient sources and cycling in aquatic systems worldwide, followed by specific examples from the Delta. These examples describe...
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Vertical deformation of extensional provinces varies significantly and in seemingly contradictory ways. Sparse but robust geodetic, seismic, and geologic observations in the Basin and Range province of the western United States indicate that immediately after an earthquake, vertical change primarily occurs as subsidence of the normal fault hanging wall. A few decades later, a ±100 km wide zone is symmetrically uplifted. The preserved topography of long-term rifting shows bent and tilted footwall flanks rising high above deep basins. We develop finite element models subjected to extensional and gravitational forces to study time-varying deformation associated with normal faulting. We replicate observations with a...
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The United States is an Arctic nation—Americans depend on the Arctic for biodiversity and climate regulation and for natural resources. America’s Arctic—Alaska—is at the forefront of rapid climate, environmental, and socio-economic changes that are testing the resilience and sustainability of communities and ecosystems. Research to increase fundamental understanding of these changes is needed to inform sound, science-based decision- and policy-making and to develop appropriate solutions for Alaska and the Arctic region as a whole. Created by an Act of Congress in 1984, and since 2010 a subcommittee of the National Science and Technology Council (NSTC) in the Executive Office of the President, the Interagency Arctic...
Categories: Publication; Types: Citation
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The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas...
Categories: Publication; Types: Citation
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The Provo shoreline of Lake Bonneville formed following the Bonneville flood, and, based on previous dating, was formed during a period of overflow from about 17.5 to 15.0 cal. ka. In many places the Provo shoreline consists of a pair of distinct shorelines, one ∼3 m higher than the other. We present data from two cuts through double beaches to show that the upper beach is younger and represents sedimentation after a lake-level rise. In addition, the lower beach deposits are internally stratified by beds that suggest three more lake-level rises during its development. The Provo beach complex thus appears to have been built during rising lake levels, which can be explained by rises in the overflow threshold by sequential...
Categories: Publication; Types: Citation; Tags: Boreas
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Measurements of in-situ magnetic susceptibility were compiled from mainly Precambrian crystalline basement rocks beneath the Colorado Plateau and ranges in Arizona, Colorado, and New Mexico. The susceptibility meter used measures about 30 cm3 of rock and measures variations in the modal distribution of magnetic minerals that form a minor component volumetrically in these coarsely crystalline granitic to granodioritic rocks. Recent measurements include 50–150 measurements on each outcrop, and show that the distribution of magnetic susceptibilities is highly variable, multimodal and strongly non-Gaussian. Although the distribution of magnetic susceptibility is well known to be multifractal, the small number of data...
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This collection of 37 short papers is the second published chapter of "Geological Survey Research 1972." The papers report on scientific and economic results of current work by members of the Conservation, Geologic, and Water Resources Divisions of the U.S. Geological Survey.Chapter A, to be published later in the year, will present a summary of significant results of work done ~n fiscal year 1972, together with lists of investigations in progress, cooperating agencies, and Geological Survey offices."Geological Survey Research 1972" is the thirteenth volume of the annual series Geological Survey Research. The twelve volumes already published are listed below, with their series designations.
Categories: Publication; Types: Citation; Tags: Professional Paper
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This report is the second in a series of three reports that provide information about high-frequency (HF) nutrient and biogeochemical monitoring in the Sacramento–San Joaquin Delta of northern California (Delta). The purpose of this report is to synthesize the data available from a nutrient and water-quality HF (about every 15 minutes) monitoring network operated by the U.S. Geological Survey in the northern Delta. In this report, we describe the network and focus on the purpose of each station. We then present and discuss the available data, at various timescales—first at the monthly, seasonal, and inter-annual timescales, and second, for comparison, at the tidal and event timescales. As expected, we determined...


map background search result map search result map Land cover disturbances and feedbacks to the climate system in Canada and Alaska Upper Cook Inlet commercial herring and smelt fisheries, 2004 Upper Cook Inlet commercial herring and smelt fisheries, 2004 Land cover disturbances and feedbacks to the climate system in Canada and Alaska