{
    "tag": 16155,
    "title": "Tone-matched enhanced TIFF sidescan-sonar image from Temple Basin and Iceberg Canyon, Lake Mead - UTM projection",
    "pubdate": "2003",
    "sername": null,
    "series_name": null,
    "issue": "03-320",
    "publish": null,
    "publisher_name": null,
    "onlink": "https:\/\/cmgds.marine.usgs.gov\/catalog\/whcmsc\/open_file_report\/ofr2003-320\/tempice_enhmeta.faq.html",
    "format": null,
    "email": null,
    "descript": "Lake Mead is a large interstate reservoir located in the Mojave Desert of southeastern Nevada and northwestern Arizona.  It was impounded in 1935 by the construction of Hoover Dam and is one of a series of multi-purpose reservoirs on the Colorado River.  The lake extends 183 km from the mouth of the Grand Canyon to Black Canyon, the site of Hoover Dam, and provides water for residential, commercial, industrial, recreational, and other non-agricultural users in communities across the southwestern United States.  Extensive research has been conducted on Lake Mead, but a majority of the studies have involved determining levels of anthropogenic contaminants such as synthetic organic compounds, heavy metals and dissolved ions, furans\/dioxins, and nutrient loading in lake water, sediment, and biota (Preissler, et al., 1998; Bevans et al, 1996; Bevans et al., 1998; Covay and Leiker, 1998; LaBounty and Horn, 1997; Paulson, 1981).  By contrast, little work has focused on the sediments in the lake and the processes of deposition (Gould, 1951).  To address these questions, sidescan-sonar imagery and high-resolution seismic-reflection profiles were collected throughout Lake Mead by the USGS in cooperation with researchers from University of Nevada Las Vegas (UNLV).  These data allow a detailed mapping of the surficial geology and the distribution and thickness of sediment that has accumulated in the lake since the completion of Hoover Dam.  Results indicate that the accumulation of post-impoundment sediment is primarily restricted to former river and stream beds that are now submerged below the lake while the margins of the lake appear to be devoid of post-impoundment sediment.  The sediment cover along the original Colorado River bed is continuous and is typically greater than 10 m thick through much of its length.  Sediment thickness in some areas exceeds 35 m while the smaller tributary valleys typically are filled with less than 4 m of sediment.  Away from the river beds that are now covered with post-impoundment sediment, pre-impoundment alluvial deposits and rock outcrops are still exposed on the lake floor.",
    "lang": null,
    "journal": null,
    "pwid": null,
    "originator": [
        {
            "name": "Twichell, David C.",
            "role": "Author"
        },
        {
            "name": "Cross, VeeAnn A.",
            "role": "Author"
        },
        {
            "name": "Belew, Stephen D.",
            "role": "Author"
        }
    ],
    "index_term": [
        {
            "thcode": 2,
            "code": "470",
            "name": "geophysics",
            "scope": "Branch of geology studying the physical characteristics and phenomena of the earth and its atmosphere."
        },
        {
            "thcode": 2,
            "code": "474",
            "name": "geospatial datasets",
            "scope": "Collections of related digital information that are geographically referenced."
        },
        {
            "thcode": 2,
            "code": "2046",
            "name": "image mosaics",
            "scope": "Composite images formed by overlapping existing images, typically arranged to achieve greater spatial coverage."
        },
        {
            "thcode": 2,
            "code": "2091",
            "name": "lakebed acoustic reflectivity",
            "scope": "Acoustic energy received by a sonar system, providing a measure of the roughness of the lakebed."
        },
        {
            "thcode": 2,
            "code": "2038",
            "name": "sidescan sonar",
            "scope": "Acoustic technique for creating oblique backscatter imagery of the seafloor or lakebed."
        },
        {
            "thcode": 15,
            "code": "008",
            "name": "geoscientificInformation",
            "scope": "Information pertaining to earth sciences, for example geophysical features and processes, geology, minerals, sciences dealing with the composition, structure and origin of the earth's rocks, risks of earthquakes, volcanic activity, landslides, gravity information, soils, permafrost, hydrogeology, groundwater, erosion"
        },
        {
            "thcode": 15,
            "code": "010",
            "name": "imageryBaseMapsEarthCover",
            "scope": "Base maps, for example land\/earth cover, topographic maps, imagery, unclassified images, annotations, digital ortho imagery"
        },
        {
            "thcode": 15,
            "code": "012",
            "name": "inlandWaters",
            "scope": "Inland water features, drainage systems and characteristics, for example rivers and glaciers, salt lakes, water utilization plans, dams, currents, floods and flood hazards, water quality, hydrographic charts, watersheds, wetlands, hydrography"
        }
    ],
    "place_term": [],
    "image": [],
    "fan": [
        "2001-007-FA"
    ]
}