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At least 1,009 records · Page 56Linked to original sources
USGS2013

Land Treatment Digital Library

The Land Treatment Digital Library (LTDL) was created by the U.S. Geological Survey to catalog legacy land treatment information on Bureau of Land Management lands in the western United States. The LTDL can be used by federal managers and scientists for compiling information for data-calls, producing maps, generating reports, and conducting analyses at varying spatial and temporal scales. The LTDL currently houses thousands of treatments from BLM lands across 10 states. Users can browse a map to find information on individual treatments, perform more complex queries to identify a set of treatments, and view graphs of treatment summary statistics.

Data Series↗
USGS2006

Database for the geologic map of the Sauk River 30-minute by 60-minute quadrangle, Washington (I-2592)

This digital map database has been prepared by R.W. Tabor from the published Geologic map of the Sauk River 30- by 60 Minute Quadrangle, Washington. Together with the accompanying text files as PDF, it provides information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The authors mapped most of the bedrock geology at 1:100,000 scale, but compiled most Quaternary units at 1:24,000 scale. The Quaternary contacts and structural data have been much simplified for the 1:100,000-scale map and database. The spatial resolution (scale) of the database is 1:100,000 or smaller. This database depicts the distribution of geologic materials and structures at a regional (1:100,000) scale. The report is intended to provide geologic information for the regional study of materials properties, earthquake shaking, landslide potential, mineral hazards, seismic velocity, and earthquake faults. In addition, the report contains information and interpretations about the regional geologic history and framework. However, the regional scale of this report does not provide sufficient detail for site development purposes.

Data Series↗
USGS2006

Database for the geologic map of the Mount Baker 30-minute by 60-minute quadrangle, Washington (I-2660)

This digital map database has been prepared by R.W. Tabor from the published Geologic map of the Mount Baker 30- by 60-Minute Quadrangle, Washington. Together with the accompanying text files as PDF, it provides information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The authors mapped most of the geology at 1:100,000. The Quaternary contacts and structural data have been much simplified for the 1:100,000-scale map and database. The spatial resolution (scale) of the database is 1:100,000 or smaller. This database depicts the distribution of geologic materials and structures at a regional (1:100,000) scale. The report is intended to provide geologic information for the regional study of materials properties, earthquake shaking, landslide potential, mineral hazards, seismic velocity, and earthquake faults. In addition, the report contains information and interpretations about the regional geologic history and framework. However, the regional scale of this report does not provide sufficient detail for site development purposes.

Washington↗
USGS1983

Hydrology of area 50, Northern Great Plains and Rocky Mountain coal provinces, Wyoming and Montana

This report is one of a series designed to characterize the hydrology of drainage basins within coal provinces, nationwide. Area 50 includes all of the Powder River Basin, Wyoming and Montana and the upstream parts of the Cheyenne and Belle Fourche River Basins - a total of 20,676 sq mi. The area has abundant coal (81.2 million tons mined in 1982), but scarce water. The information in the report is intended to describe the hydrology of the ' general area ' of any proposed mine. The report represents a summary of results of the water resources investigations of the U.S. Geological Survey, carried out in cooperation with State and other Federal agencies. Each of more than 50 topics is discussed in a brief text that is accompanied by maps, graphs, and other illustrations. Primary topics in the report are: physiography, economic development, surface-water data networks, surface water quantity and quality, and groundwater. The report also contains an extensive description of sources of additional information. (USGS)

Open-File Report↗
USGS2004

Data compilation, synthesis, and calculations used for organic-carbon storage and inventory estimates for mineral soils of the Mississippi River Basin

U.S. Geological Survey investigations of environmental controls on carbon cycling in soils and sediments of the Mississippi River Basin (MRB), an area of 3.3 x 106 square kilometers (km2), have produced an assessment tool for estimating the storage and inventory of soil organic carbon (SOC) by using soil-characterization data from Federal, State, academic, and literature sources. The methodology is based on the linkage of site-specific SOC data (pedon data) to the soil-association map units of the U.S. Department of Agriculture State Soil Geographic (STATSGO) and Soil Survey Geographic (SSURGO) digital soil databases in a geographic information system. The collective pedon database assembled from individual sources presently contains 7,321 pedon records representing 2,581 soil series. SOC storage, in kilograms per square meter (kg/m2), is calculated for each pedon at standard depth intervals from 0 to 10, 10 to 20, 20 to 50, and 50 to 100 centimeters. The site-specific storage estimates are then regionalized to produce national-scale (STATSGO) and county-scale (SSURGO) maps of SOC to a specified depth. Based on this methodology, the mean SOC storage for the top meter of mineral soil in the MRB is approximately 10 kg/m2, and the total inventory is approximately 32.3 Pg (1 petagram = 109 metric tons). This inventory is from 2.5 to 3 percent of the estimated global mineral SOC pool.

Professional Paper↗
USGS1962

Lake Bonneville: Geology of southern Cache Valley, Utah

This report, covering about 450 square miles in southern Cache Vally, Utah, is one of a series dealing with the geology of Pleistocene Lake Bonneville. The report summarizes in tabular form the Paleozoic formations that are exposed in the mountains adjacent to Cache Valley and describes briefly the Tertiary formations—the Wasatch and Salt Lake formations— which are exposed in the valley. Most of the report deals with the Quaternary deposits. Fan gravel and landslides of pre-Lake Bonneville Quaternary age are exposed in a few places at the edges of the basin, and well logs indicate a deep fill of this age in the subsurface of the basin interior. The sediments of Lake Bonneville comprise the Lake Bonneville group. The oldest of the unconsolidated deposits are the Alpine and Bonneville formations, which were mostly mapped together in southern Cache Valley. These formations are composed mostly of silt, but they include some gravel in embankments and small deltas. Their thickness ranges from about 50 to 100 feet. Overlying the Alpine and Bonneville formations is the Provo formation 50 to 75 feet thick. In Cache Valley, as elsewhere in the Lake Bonneville basin, the Provo includes extensive gravel deposits in bars, spits, and deltas. It is the surface formation in much of Cache Valley. Deposits younger than the Provo, mostly of Recent age, include alluvial flans, flood-plain alluvium, natural levee deposits along the Bear River, slope wash, eolian sand, and cones of spring tufa. Several faults, active in Tertiary time, are mapped. Well logs indicate that the pre-Lake Bonneville deposits of Quaternary age are surprisingly thin in Cache Valley, suggesting that the valley had exterior drainage during most of Pleistocene time. The logs show two main aquifers of gravel and sand— the upper one between the Provo formation and the Alpine and Bonneville formations and the other directly beneath the Alpine and Bonneville deposits. These aquifers probably are alluvium deposited during interlake intervals. The shore embankments and deltas of the Lake Bonneville group are abundant sources of gravel and sand for construction. Much of the gravel is suitable for concrete aggregate.

Utah↗
USGS2006

Database for the geologic map of the Snoqualmie Pass 30-minute by 60-minute quadrangle, Washington (I-2538)

This digital map database has been prepared by R.W. Tabor from the published Geologic map of the Snoqualmie Pass 30' X 60' Quadrangle, Washington. Together with the accompanying text files as PDF, it provides information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The authors mapped most of the bedrock geology at 1:100,000 scale, but compiled Quaternary units at 1:24,000 scale. The Quaternary contacts and structural data have been much simplified for the 1:100,000-scale map and database. The spatial resolution (scale) of the database is 1:100,000 or smaller. This database depicts the distribution of geologic materials and structures at a regional (1:100,000) scale. The report is intended to provide geologic information for the regional study of materials properties, earthquake shaking, landslide potential, mineral hazards, seismic velocity, and earthquake faults. In addition, the report contains information and interpretations about the regional geologic history and framework. However, the regional scale of this report does not provide sufficient detail for site development purposes.

Data Series↗
USGS2015

U.S. Geological Survey groundwater toolbox, a graphical and mapping interface for analysis of hydrologic data (version 1.0): user guide for estimation of base flow, runoff, and groundwater recharge from streamflow data

This report is a user guide for the streamflow-hydrograph analysis methods provided with version 1.0 of the U.S. Geological Survey (USGS) Groundwater Toolbox computer program. These include six hydrograph-separation methods to determine the groundwater-discharge (base-flow) and surface-runoff components of streamflow—the Base-Flow Index (BFI; Standard and Modified), HYSEP (Fixed Interval, Sliding Interval, and Local Minimum), and PART methods—and the RORA recession-curve displacement method and associated RECESS program to estimate groundwater recharge from streamflow data. The Groundwater Toolbox is a customized interface built on the nonproprietary, open source MapWindow geographic information system software. The program provides graphing, mapping, and analysis capabilities in a Microsoft Windows computing environment. In addition to the four hydrograph-analysis methods, the Groundwater Toolbox allows for the retrieval of hydrologic time-series data (streamflow, groundwater levels, and precipitation) from the USGS National Water Information System, downloading of a suite of preprocessed geographic information system coverages and meteorological data from the National Oceanic and Atmospheric Administration National Climatic Data Center, and analysis of data with several preprocessing and postprocessing utilities. With its data retrieval and analysis tools, the Groundwater Toolbox provides methods to estimate many of the components of the water budget for a hydrologic basin, including precipitation; streamflow; base flow; runoff; groundwater recharge; and total, groundwater, and near-surface evapotranspiration.

Techniques and Methods↗
USGS2015

Groundwater conditions in Utah, spring of 2015

This is the fifty-second in a series of annual reports that describe groundwater conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Department of Natural Resources, Division of Water Rights, and the Utah Department of Environmental Quality, Division of Water Quality, provide data to enable interested parties to maintain awareness of changing groundwater conditions. This report, like the others in the series, contains information on well construction, groundwater withdrawals from wells, water-level changes, precipitation, streamflow, and chemical quality of water. Information on well construction included in this report refers only to new wells constructed for withdrawal of groundwater. Supplementary data are included in reports of this series only for those years or areas that are important to a discussion of changing groundwater conditions and for which applicable data are available. This report includes individual discussions of selected significant areas of groundwater development in the State for calendar year 2014. Most of the reported data were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights, and the Utah Department of Environmental Quality, Division of Water Quality. This report is also available online at http://www.waterrights.utah.gov/techinfo/ and http://ut.water.usgs.gov/publications/GW2015.pdf. Groundwater conditions in Utah for calendar year 2013 are reported in Burden and others (2014) and are available online at http://ut.water.usgs.gov/publications/GW2014.pdf. The water-level change maps in this report show the difference between water levels measured in the same well at two distinct times: in the spring of 1985 and the spring of 2015. Throughout the state, many groundwater levels were near their peak in or around 1985 following a multiple-year period of above average precipitation in the early 1980s. Conversely, consecutive years of significant drought have contributed to low groundwater levels in 2015. For these reasons, the difference between 1985 and 2015 groundwater levels may not accurately portray long-term changes in an aquifer. An evaluation of water-level trends should also include consideration of the annual water-level measurement plots provided for each of the major areas of groundwater development in this report.

Utah↗
USGS2025

Groundwater-level elevations in the Denver Basin bedrock aquifers and Upper Black Squirrel Creek alluvial aquifer, El Paso County, Colorado, 2021–24

El Paso County is the second-most populous county in Colorado and is projected to grow another 15 percent by 2030. Within El Paso County is the Upper Black Squirrel Creek Designated Groundwater Basin (Black Squirrel Basin), an area where surface water is scarce and water users rely primarily on groundwater from five different aquifers (the Upper Black Squirrel Creek alluvial aquifer and four bedrock aquifers within the Denver Basin aquifer system: the lower Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers) to meet their needs. Currently (2024), land within the Upper Black Squirrel Creek Basin is primarily used for rural grazing and agriculture; however, municipal development is ongoing. In 2021, the U.S. Geological Survey, in cooperation with the Upper Black Squirrel Creek Ground Water Management District, began a study to establish a baseline dataset and assess the groundwater resources of the aquifers within the Black Squirrel Basin. A network of 39 wells was established in 2021; discrete groundwater-level measurements were made bimonthly. Nine of the 39 wells were equipped with pressure transducers to record hourly groundwater-level data. Seven wells had statistically significant seasonal trends, and trends at 3 wells were negative. For the discrete data, 16 wells had a significant trend for the study period, and 4 wells had negative trends. For the time-series data, 8 wells had significant trends, and 3 wells had negative trends. Potentiometric surface maps were created for this study using discrete, static groundwater levels measured in April 2023. These maps showed the estimated groundwater flow direction from the north-northwest to the south-southeast in the alluvial aquifer and from the northwest to the east-southeast for the lower Dawson and Denver aquifer wells. This study indicates the potential benefit of monitoring wells in the areas near municipal pumping. Additional monitoring could lead to a better understanding of connectivity between aquifers and be an important tool for assessing long-term sustainability of groundwater use.

Colorado↗
USGS2026

Geologic map of pre-Middle Jurassic basement rocks beneath the Atlantic and Gulf Coastal Plains in Florida

Much of the southeastern United States, including all of Florida, is covered by flat-lying sedimentary strata of the Atlantic and Gulf Coastal Plains which have accumulated since Middle Jurassic time. The pre-Middle Jurassic rocks that underlie these coastal plains in Florida, here collectively referred to as “basement,” are known only from a relatively small number of boreholes. This scientific investigations map presents an interpretation of the basement geology in a 1:1,000,000-scale subsurface geologic map with supporting text, data, and figures. The subsurface mapping methodology integrates petrographic, geochronological, thermochronological, geochemical, and mineralogical analyses of drill cores and cuttings in the context of regional geophysical data. The pre-Middle Jurassic rocks of Florida consist of the Gondwanan (West African) Suwannee terrane which was accreted to Laurentia during the Alleghanian orogeny and subsequently intruded by Permian granites, superposed by early Mesozoic rift basins, and partially overlain by bimodal Jurassic volcanic rocks. The younger basement components, specifically the Southwest Florida volcanic province, North Florida tholeiites, early Mesozoic rift basins, and Alleghanian granitoids, have correlative and contemporaneous units throughout the Appalachian orogen. In contrast, Florida’s older basement rocks, including Paleozoic siliciclastic strata of the Suwannee basin, North Florida volcanic series, Osceola and Gaskin intrusive complexes, and the St. Lucie Metamorphic Complex, have neither surface exposures nor unequivocal correlates. Major structures include early Mesozoic normal faults and northwest-striking transfer zones such as the Jay fault. Many of these faults define the boundaries of subbasins within the South Georgia rift system. Top-of-basement structure contours show gentle arches and embayments that are also recognized in overlying coastal plain strata.

Florida↗
USGS2007

Ground water flow modeling with sensitivity analyses to guide field data collection in a mountain watershed

In mountain watersheds, the increased demand for clean water resources has led to an increased need for an understanding of ground water flow in alpine settings. In Prospect Gulch, located in southwestern Colorado, understanding the ground water flow system is an important first step in addressing metal loads from acid-mine drainage and acid-rock drainage in an area with historical mining. Ground water flow modeling with sensitivity analyses are presented as a general tool to guide future field data collection, which is applicable to any ground water study, including mountain watersheds. For a series of conceptual models, the observation and sensitivity capabilities of MODFLOW-2000 are used to determine composite scaled sensitivities, dimensionless scaled sensitivities, and 1% scaled sensitivity maps of hydraulic head. These sensitivities determine the most important input parameter(s) along with the location of observation data that are most useful for future model calibration. The results are generally independent of the conceptual model and indicate recharge in a high-elevation recharge zone as the most important parameter, followed by the hydraulic conductivities in all layers and recharge in the next lower-elevation zone. The most important observation data in determining these parameters are hydraulic heads at high elevations, with a depth of less than 100 m being adequate. Evaluation of a possible geologic structure with a different hydraulic conductivity than the surrounding bedrock indicates that ground water discharge to individual stream reaches has the potential to identify some of these structures. Results of these sensitivity analyses can be used to prioritize data collection in an effort to reduce time and money spend by collecting the most relevant model calibration data.

Groundwater Monitoring & Remediation↗
USGS1995

Geologic map of the Hayward fault zone, Contra Costa, Alameda, and Santa Clara counties, California: A digital database

The Hayward is one of three major fault zones of the San Andreas system that have produced large historic earthquakes in the San Francisco Bay Area (the others being the San Andreas and Calaveras). Severe earthquakes were generated by this fault zone in 1836 and in 1868, and several large earthquakes have been recorded since 1868. The Hayward fault zone is considered to be the most probable source of a major earthquake in the San Francisco Bay Area, as much as 28% chance for a magnitude 7 earthquake before the year 2021 (Working Group on California Earthquake Probabilities, 1990). The Hayward fault zone, as described in this work, is a zone of highly deformed rocks, trending north 30 degrees west and ranging in width from about 2 to 10 kilometers. The historic earthquake generating activity has been concentrated in the western portion of the zone, but the zone as a whole reflects deformation derived from oblique right-lateral and compressive tectonic stress along a significant upper crustal discontinuity for the past 10 million or more years. The Hayward fault zone is bounded on the east by a series of faults that demarcate the beginning of one or more structural blocks containing rocks and structures unrelated to the Hayward fault zone. The eastern bounding faults are, from the south, the Calaveras, Stonybrook, Palomares, Miller Creek, and Moraga faults. These faults are not considered to be part of the Hayward fault zone, although they are shown on the map to demarcate its boundary. The western boundary of the zone is less clearly defined, because the alluvium of the San Francisco Bay and Santa Clara Valley basins obscures bedrock and structural relationships. Although several of the westernmost faults in the zone clearly project under or through the alluvium, the western boundary of the fault is generally considered to be the westernmost mapped fault, which corresponds more or less with the margin of thick unconsolidated surficial deposits. The Hayward fault zone is truncated to the south by the Calaveras fault, which trends about north 10 west, and so forms an oblique east and south boundary. All of the faults within the southern part of the zone probably splay into the Calaveras fault. The northern margin of the zone as dealt with herein is San Pablo Bay, but the zone of deformation undoubtedly continues north of the Bay through the area bounded by the Rodgers Creek and Tolay faults.

California↗
USGS1952

Geology of the Quartz Creek Pegmatite District, Gunnison County Colorado

The Quartz Creek pegmatite district includes an area about 29 square miles in the vicinity of Quartz Creek in Gunnison County,. Colo. This area contains 1,803 pegmatites that are intruded into pre-Cambrian rocks. The rocks exposed in the district range in age from pre-Cambrian to Recent. The oldest pre-Cambrian rocks are chiefly quartzites interbedded with a few arkoses and conglomerates. These rocks are surrounded by more abundant hornblende gneiss and tonalite. A small body of biotite tonalite was intruded and two thin layers of dacitic pillow lava were extruded into this series. The hornblende gneiss and tonalite have the same composition and differ only in texture. The older material (hornblende gneiss) has a well-marked lineation, whereas the younger (tonalite) is equigranular. Subsequently, a large body of quartz monzonite was intruded along the northern boundary of the mapped area. Later, coarse-grained granite was intruded into the southern part of the area. Dikes of fine-grained granite cut the coarse-grained variety. The last period of intrusive activity in pre-Cambrian time is marked by a large number of pegmatites. The pre-Cambrian rocks were tilted and eroded, and the flatlying Jurassic Morrison formation was deposited on the irregular surface. This formation is conformably overlain by the Cretaceous Dakota sandstone. Faulting produced a vertical offset of 410 feet in the Mesozoic sediments along the only large fault in the area. At the end of Mesozoic time there was another period of erosion. Tertiary (?) tuff is exposed in small, scattered areas in the southern part of the district. It overlies both the Dakota sandstone and pre-Cambrian formations. Glacial till occurs along the edges of Quartz Creek and Wood Gulch. Quaternary alluvium fills the valley bottoms. Although the composition of the country rock has little effect on the shape of the pegmatites, the foliation imposed on this rock has a localizing effect and in part controls the ultimate shape of pegmatites. Zoned and related internal structures are not well developed in the pegmatites of this region. Many of the pegmatites are homogeneous and those that are zoned usually contain a large wall zone and small discontinuous cores. In addition to the more common homogeneous and zoned pegmatites, 7 percent of the pegmatites show a layered structure of textural and mineralogical units not repeated on the opposite side of the pegmatite. Other internal structural units include pegmatites which vary in composition along strike, multiple or “line-rock pegmatites” and fracture fillings. The mineralogy of the pegmatites is described in detail. Specific attention was given to most of the 27 observed minerals. A study of the index of refraction of 439 specimens of plagioclase showed that the variation from zone to zone and layer to layer is minor and that there is no systematic variation in respect to the entire district. No correlation could be found between the refractive index of plagioclase in the pegmatites and the type country rock, or the presence of various accessory minerals. Index of refraction determinations on 95 specimens of muscovite showed no constant variation from wall zone to core or from layer to layer. Curved muscovite has identical optical properties with the flat variety. The index of refraction was determined for 189 beryl specimens. The beryl in the pegmatites containing only a wall zone and a core showed no difference between zones, but in pegmatites that have intermediate zones, the indices of refraction of the beryl showed an inward increase in the alkali content from the contact. Beryl occurs with almost all of the pegmatite minerals and is not restricted in its mineral associations. Tourmaline, except the black variety, is associated with lepidolite. Dark green and blue tourmaline is found in the outer zones of pegmatites containing lepidolite, and the pink and light green varieties are found in direct contact with lepidolite. Lepidolite occurs in aggregates of fine grains, in flat plates, and in curved plates; the three varieties are optically identical. The lighter-colored varieties have higher indices of refraction and contain less lithia than the darker varieties. In addition, the occurrence of the following minerals is described in detail: perthite, quartz, martite, biotite, garnet, columbite-tantalite, monazite, microlite, topaz, gahnite, allanite, and an unidentified mineral. The lack of alteration in the wall rocks adjacent to the pegmatites is interpreted as indicating that the original pegmatite magma did not have an excess of materials such as B, OH-, and P that are needed to form alteration minerals. Because of their low concentration, the above materials were available only in the pegmatitic magma during its crystallization. Pegmatites that contain the rare minerals such as beryl, tourmaline, curved muscovite, biotite, magnetite, monazite, columbite-tantalite, cleavelandite, topaz, lepidolite, and microlite show a grouping in clusters within the district. Beryl-bearing pegmatites occur most abundantly in hornblende gneiss and are only rarely found in either granite or quartz monzonite. The types of minerals that form in a pegmatite appear to be determined by the character of the material segregated from the original magma and the period in which it segregated. The elements escape at one period and may be from only-a specific pocket in the magma. These liquids tend to form groups of pegmatites in which the later bodies contain a high proportion of volatiles. Inferred reserves of the district are estimated for beryl, scrap mica, both hand-cobbing and milling feldspar, lepidolite, columbite-tantalite, topaz, monazite, and microlite. No sheet mica was found. Reserves are small and transportation costs are high so substantial production of low-priced feldspar and scrap mica will depend on the adoption of economica milling techniques for recovering the large quantities of feldspar available. Beryl is irregularly distributed and its recovery as a byproduct will depend on the establishment of a stable market for feldspar and scrap mica. Lepidolite reserves are small low grade.

Colorado↗
USGS2004

Digital data to support development of a pesticide management plan for the Standing Rock Indian Reservation, Sioux County, North Dakota, and Corson County, South Dakota

As part of a program to support development of pesticide management plans for Indian Reservations, the U.S. Geological Survey has been working in cooperation with the U.S. Environmental Protection Agency to make selected information available to the Tribes or in a format easier for the Tribes to use. As a result of this program, four digital data sets related to the geology or hydrology of the Standing Rock Indian Reservation were produced as part of this report. The digital data sets are based on maps published in 1982 at the 1:250,000 scale in "Geohydrology of the Standing Rock Indian Reservation, North and South Dakota," U.S. Geological Survey Hydrologic Investigations Atlas HA-644 by L.W. Howells. The digital data sets were created by 1) scanning the appropriate map to create an image file, 2) registering the image file to real-world coordinates, 3) creating a new image file rectified to real-world coordinates, and 4) digitizing of the features of interest using the rectified image as a guide. As digital data sets, the information can be used in a geographic information system in combination with other information to help develop a pesticide management plan.

Data Series↗
USGS2012

High-resolution digital elevation dataset for Crater Lake National Park and vicinity, Oregon, based on LiDAR survey of August-September 2010 and bathymetric survey of July 2000

Crater Lake partially fills the caldera that formed approximately 7,700 years ago during the eruption of a 12,000-foot volcano known as Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama devastated the surrounding landscape, left a thick deposit of pumice and ash in adjacent valleys, and spread a blanket of volcanic ash as far away as southern Canada. Because the Crater Lake region is potentially volcanically active, knowledge of past events is important to understanding hazards from future eruptions. Similarly, because the area is seismically active, documenting and evaluating geologic faults is critical to assessing hazards from earthquakes. As part of the American Recovery and Reinvestment Act (ARRA) of 2009, the U.S. Geological Survey was awarded funding for high-precision airborne LiDAR ( Li ght D etection A nd R anging) data collection at several volcanoes in the Cascade Range through the Oregon LiDAR Consortium, administered by the Oregon Department of Geology and Mineral Industries (DOGAMI). The Oregon LiDAR Consortium contracted with Watershed Sciences, Inc., to conduct the data collection surveys. Collaborating agencies participating with the Oregon LiDAR Consortium for data collection in the Crater Lake region include Crater Lake National Park (National Park Service) and the Federal Highway Administration. In the immediate vicinity of Crater Lake National Park, 798 square kilometers of LiDAR data were collected, providing a digital elevation dataset of the ground surface beneath forest cover with an average resolution of 1.6 laser returns/m 2 and both vertical and horizontal accuracies of ±5 cm. The LiDAR data were mosaicked in this report with bathymetry of the lake floor of Crater Lake, collected in 2000 using high-resolution multibeam sonar in a collaborative effort between the U.S. Geological Survey, Crater Lake National Park, and the Center for Coastal and Ocean Mapping at the University of New Hampshire. The bathymetric survey collected 16 million soundings with a spatial resolution of 2 meters using an EM1002 system owned and operated by C&C Technologies, Inc. The combined LiDAR and bathymetric dataset has a cell size of 1 meter and will contribute to understanding past volcanic events and their deposits, recognizing of faults and volcanic landforms, and quantifying landscape modification during and after the next volcanic eruption at Crater Lake.

Oregon↗
USGS2003

The Long Valley Caldera GIS database

This database provides an overview of the studies being conducted by the Long Valley Observatory in eastern California from 1975 to 2001. The database includes geologic, monitoring, and topographic datasets related to Long Valley caldera. The CD-ROM contains a scan of the original geologic map of the Long Valley region by R. Bailey. Real-time data of the current activity of the caldera (including earthquakes, ground deformation and the release of volcanic gas), information about volcanic hazards and the USGS response plan are available online at the Long Valley observatory web page (http://lvo.wr.usgs.gov). If you have any comments or questions about this database, please contact the Scientist in Charge of the Long Valley observatory.

Data Series↗
USGS1991

Major results of gravity and magnetic studies at Yucca Mountain, Nevada

About 4,000 gravity stations have been obtained at Yucca Mountain and vicinity since the beginning of radioactive-waste studies there in 1978. These data have been integrated with data from about 29,000 stations previously obtained in the surrounding region to produce a series of Bouguer and isostatic-residual-gravity maps of the Nevada Test Site and southeastern Nevada. Yucca Mountain is characterized by a WNW-dipping gravity gradient whereby residual values of -10 mGal along the east edge of Yucca Mountain decrease to about -38 mGal over Crater Flat. Using these gravity data, two-dimensional modeling predicted the depth to pre-Cenozoic rocks near the proposed repository to be about 1,220??150 m, an estimate that was subsequently confirmed by drilling to be 1,244 m. Three-dimensional modeling of the gravity low over Crater Flat indicates the thickness of Cenozoic volcanic rocks and alluvial cover to be about 3,000 m. Gravity interpretations also identified the Silent Canyon caldera before geologic mapping of Pahute Mesa and provided an estimate of the thickness of the volcanic section there of nearly 5 km.

Conference Paper↗