Geologic framework and processes of Lake Pontchartrain, Louisiana
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Geology topics
Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey
Publications and source records attributed to Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey.
U.S. Geological Survey World Wide Web Information
The U.S. Geological Survey (USGS) invites you to explore an earth science virtual library of digital information, publications, and data. The USGS World Wide Web sites offer an array of information that reflects scientific research and monitoring programs conducted in the areas of natural hazards, environmental resources, and cartog-raphy. This list provides gateways to access a cross section of the digital information on the USGS World Wide Web sites.
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Map scales
To be most useful, a map must show locations and distances accurately on a sheet of paper of convenient size. This means that all things included in the map-ground area, rivers, lakes, roads, distances between features, and so on must be shown proportionately smaller than they really are. The proportion chosen for a particular map is its scale.
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Digital orthophoto quadrangles
A digital orthophoto quadrangle (DOQ) is a computer-generated image of an aerial photograph in which image displacement caused by terrain relief and camera tilts has been removed. It combines the image characteristics of a photograph with the geometric qualities of a map.
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US GeoData Digital Elevation Models
Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The U.S. Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.
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Ordering procedures for photographic enlargement products--NAPP, NHAP, and custom
Established in 1987, the National Aerial Photography Program (NAPP) collects aerial photographs of the 48 conterminous States on a 5-year cycle. Copies of NAPP images are available in black-and-white and (or) color- Figure 1. NAPP paper-print sizes and their corresponding scales for standard enlargements.* infrared film at 1 :40,000 scale. Figure 1 shows NAPP paper-print sizes and their corresponding scales for standard enlargements.
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U.S. Geological Survey Information Sources
As the nation's largest water, earth and biological science and civilian mapping agency, the U.S. Geological Survey (USGS) works in cooperation with more than 2000 organizations across the country to provide reliable, impartial, scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, to contribute to the conservation and the sound economic and physical development of the nation's natural resources, and to enhance the quality of life by monitoring water, biological, energy and mineral resources.
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Educational materials from the U.S. Geological Survey
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Center for Integration of Natural Disaster Information
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US GeoData Available Through the Internet
The U.S. Geological Survey (USGS) offers certain US GeoData data sets through the Internet. They can be retrieved using the World Wide Web or anonymous File Transfer Protocol (FTP). The data bases and their directory paths are as follows: * 1:24,000-scale digital line graph data in SDTS format (/pub/data/DLG/24K) * 1:2,000,000-scale digital line graph data in SDTS format (/pub/data/DLG/2M) * 1:100,000-scale digital line graph data (/pub/data/DLG/100K) * 1:100,000-scale land use and land cover data (/pub/data/LULC/100K) * 1:250,000-scale land use and land cover data (/pub/data/LULC/250K) * 1:24,000-scale digital elevation data (/pub/data/DEM/7.5min) * 1-degree digital elevation model data (/pub/data/DEM/250)
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Revision of Primary Series Maps
In 1992, the U.S. Geological Survey (USGS) completed a 50-year effort to provide primary series map coverage of the United States. Many of these maps now need to be updated to reflect the construction of new roads and highways and other changes that have taken place over time. The USGS has formulated a graphic revision plan to help keep the primary series maps current. Primary series maps include 1:20,000-scale quadrangles of Puerto Rico, 1:24,000- or 1:25,000-scale quadrangles of the conterminous United States, Hawaii, and U.S. Territories, and 1:63,360-scale quadrangles of Alaska. The revision of primary series maps from new collection sources is accomplished using a variety of processes. The raster revision process combines the scanned content of paper maps with raster updating technologies. The vector revision process involves the automated plotting of updated vector files. Traditional processes use analog stereoplotters and manual scribing instruments on specially coated map separates. The ability to select from or combine these processes increases the efficiency of the National Mapping Division map revision program.
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U.S. talc; baby powder and much more
When most people think of talc, they probably envision talcum and baby powder. Since talc is very soft and easily carved, one might also think of sculptures in soapstone (massive talc). In fact, these uses of talc are quite minor compared to its wide variety of applications in manufacturing and agriculture. High-quality (pure) talc has many physical and chemical properties favorable for its use, such as its softness, purity, fragrance retention, whiteness, luster, moisture content, oil and grease adsorption, chemical inertness, low electrical conductivity, high dielectric strength, and high thermal conductivity (Virta, 1998).
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