|
||||||
|
|
|||||||
|
||||||||
|
Release of usSEABED Offshore Sediment Data for the Atlantic Coast Region—a Tool for GIS Mapping and Research
Explosive population growth and development are affecting all coastal regions of the Nation, and demographic projections indicate that people will continue moving to the coast, putting more people and development at increased risk from natural hazards. With the prospect of global climate change likely causing increased storminess and accelerated sea-level rise, coastal regions will be even more dynamic and vulnerable to erosion and storm-surge flooding. Continental-shelf regions adjacent to the U.S. mainland are products of complex geologic histories and dynamic oceanographic processes, dominated by marine transgression during Pleistocene and Holocene time (a rise in sea level of more than 100 m during the past 20,000 years). The Nation's Exclusive Economic Zone, generally defined as the area extending 200 nautical miles seaward from the coast, is larger than the continental United States and contains submerged landforms that provide various natural and societal benefits. These landforms serve as critical habitats for fisheries, landmarks for navigation, and sites for engineering activities (for example, oil and gas platforms, pipeline and cable routes, and potential wind-energy-generation sites). Some parts of the continental margins contain unconsolidated hard-mineral deposits, such as sand and gravel, which are regarded as potential aggregate resources to meet beach-nourishment needs or to augment aggregate resources from onshore deposits. A better understanding of the sea floor off the United States is also of growing concern for specialists in homeland security. The USGS, in collaboration with other Federal agencies, coastal States, and universities, is leading a Nation-wide program to gather existing marine geologic data into a fully integrated digital database called usSEABED. This innovative database, which combines a broad array of physical data and information about the sea floor, including textural, statistical, geochemical, geophysical, and compositional information, is being used to produce a suite of maps of sea-floor characteristics suitable for use in any geographic information system (GIS). These maps are part of ongoing efforts to conduct regional assessments of potential marine sand and gravel resources and to map sea-floor habitats; however, GIS products from usSEABED can also be used by planners and managers for numerous other purposes. The first of the data releases, usSEABED: Atlantic Coast Offshore Surficial Sediment Data Release, version 1, was published in 2005 as USGS Data Series 118. This report was coauthored by Jamey Reid, Jane Reid, Larry Poppe, the late Polly Hastings, Jeff Williams (all USGS), and Chris Jenkins of the University of Colorado. Other such publications for the Gulf of Mexico and the Caribbean (USGS Data Series 146, Buczkowski and others) and the Pacific coast (USGS Data Series 182, Reid and others) will be published over the next few months. Data are currently being compiled for sea-floor areas off Alaska and Hawaii. Each publication will be updated as additional data become available, with notices about these updates and other information posted on the usSEABED Web site. The data supplied in these reports are made available with geographic coordinates so that the data can be incorporated into any GIS product. Layers include numeric data from field or laboratory measurements (extracted, or EXT), numeric data from word-based descriptions (parsed, or PRS), data mined from the EXT and PRS data files using known relations (calculated, or CLC), composition and feature data of the sea floor as individual components (CMP), and combined facies (FAC) output files, along with base-map layers compiled in an Arc-View project file. The database currently includes more than 340,000 stations of sea-floor and sediment data. Federal Geographic Data Committee metadata are included, with data layers in three formats: HTML, FAQ, and text. In an effort to make the data more accessible to the public, geographically relevant subsets of DS 118 are being posted by Matthew Arsenault (USGS) to State GIS clearinghouse Web sites, such as the Rhode Island Geographic Information System and the Florida Geographic Data Library. Many of these sites serve as the primary source of GIS information for State and local agencies. The response from the State clearinghouses has been both positive and enthusiastic. Most of the holdings on these sites are for terrestrial features, and the addition of usSEABED data constitutes a substantial expansion of their coverage. As an added bonus, many of the clearinghouses have helped the USGS usSEABED team establish additional connections with local agencies and their data collections. Within regions of dense, high-quality data coverage on the continental margin, such as the New York Bight, usSEABED is being used to generate maps of sea-floor sediment types, such as gravel, sand, and mud. The database can also be used to generate maps of various other seabed parameters, such as areas of hard ground, texture classification, color, carbonate content, organic-carbon content, sea-floor roughness, and sediment shear stress. The resultant GIS sea-floor maps are providing fresh scientific insights into the geologic character and history of continental margins.
|
 |
in this issue:
special feature:
|
|||||||||||||||||||||||||
U. S. Department of the Interior | U.S. Geological Survey
previous story
