Skip to main content
Advanced Search

Filters: Tags: Marine Geology (X)

572 results (309ms)   

Filters
Date Range
Extensions
Types
Contacts
Categories
Tag Types
Tag Schemes
View Results as: JSON ATOM CSV
thumbnail
A nearshore-bar system was surveyed periodically through a storm and the following recovery period. The data showed a very rapid response of morphology to changing wave conditions and allowed various models on bar formation to be tested. Under low-energy conditions prior to the storm a small bar was surveyed 13 m offshore. Both the high reflectivity of the beach and the cross-shore distance to the bar are consistent with a model of sediment convergence at the node or antinode of a standing wave of incident period. Such a small-scale bar may be a common feature on beaches with steep foreshores and more gentle offshore slopes. With the increase in wave height during the storm, the bar became better developed and migrated...
Categories: Publication; Types: Citation; Tags: Marine Geology
thumbnail
Samples of total suspended matter (TSM) were collected at the surface over the northern outer continental margin of the Bering Sea during the summers of 1980 and 1981. Volume concentrations of surface TSM averaged 0.6 and 1.1 mg l-1 for 1980 and 1981, respectively. Organic matter, largely plankton, made up about 65% of the near-surface TSM for both years. Distributions of TSM suggested that shelf circulation patterns were characterized either by meso- and large- scale eddies or by cross-shelf components of flow superimposed on a general northwesterly net drift. These patterns may be caused by large submarine canyons which dominate the physiography of this part of the Bering Sea continental margin. ?? 1987.
Categories: Publication; Types: Citation; Tags: Marine Geology
thumbnail
Tidal resuspension experiments were carried out on two occasions during the winter of 1988-1989 at a disposal site for hydraulically dredged sediments in northern Chesapeake Bay to determine the influence of tidal resuspension on erosion of recent deposits. The results indicate that normal tidal erosion depths were only a fraction of a millimeter per half tidal cycle and probably did not account for the majority of the apparent sediment loss. Erosion rate was found to be a linear function of the excess of estimated shear stress over a critical value, but both the constant of proportionality (M = 0.5 mg/cm2/h) and the critical shear stress (??c = 0.16 dynes/cm2 were much less than many previously reported results....
Categories: Publication; Types: Citation; Tags: Marine Geology
thumbnail
The storm-protected continental shelf of Monterey Bay, part of the Monterey Bay National Marine Sanctuary, north-central California, is subject to abundant, episodic sediment input from fluvial sources. North of Monterey Bay, conditions of reduced sediment supply combined with the exposed nature of the shelf provide an effective laboratory for studying the contrasting effects of storm- versus fluvial-dominated conditions on modern sedimentation. Textural analyses performed on surface sediment samples collected from more than 380 box cores and MultiCores??? document the existence of a clearly defined mud belt occupying the mid-shelf throughout the region. Inshore sands combined with these mid-shelf muds represent...
Categories: Publication; Types: Citation; Tags: Marine Geology
thumbnail
Geophysical and geological survey data were collected off Town Neck Beach in Sandwich, Massachusetts, in May and July 2016. Approximately 130 linear kilometers of subbottom (seismic-reflection) and 234-kilohertz interferometric sonar (bathymetric and backscatter) data were collected along with sediment samples, sea floor photographs, and (or) video at 26 sites within the geophysical survey area. Sediment grab samples were collected at 19 of the 26 sampling sites and video and (or) photographic imagery of the sea floor were taken at all 26 sites. These survey data are used to characterize the sea floor by identifying sediment-texture, seabed morphology, and underlying geologic structure and stratigraphy. Data collected...
thumbnail
Aerial photographs of the coastline from Teller to Nome were collected between August 26, 2015 - August 27, 2015. The photographs were processed using Structure-from-Motion (SfM) photogrammetric techniques. Global Positioning System (GPS) checkpoints were collected via a Global Navigation Satellite System (GNSS) survey conducted between August 15 and September 14, 2015. For the purposes of open access to elevation and orthoimagery datasets in coastal regions of Alaska, this collection is being released as a Raw Data File with an open end-user license. This file is a single-band, 32-bit float DSM (digital surface model) which represents surface elevations of buildings, vegetation, and uncovered ground surfaces in...
thumbnail
Surveys of the bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site (HARS), offshore of New York and New Jersey, were carried out in 1996, 1998, and 2000 using a Simrad EM1000 multibeam echosounder mounted on the Canadian Coast Guard ship Frederick G. Creed. The objective of the multiple echosounder surveys was to map the bathymetry and surficial sediments over time as dredged material was placed in the HARS to remediate contaminated sediments. Maps derived from the multibeam surveys show sea-floor bathymetry, shaded-relief bathymetry, and backscatter intensity (a measure of sea-floor texture and roughness) at a spatial resolution of three meters. The area was mapped by the...
thumbnail
Sandy ocean beaches in the United States are popular tourist and recreational destinations and constitute some of the most valuable real estate in the country. The boundary between land and water along the coastline is often the location of concentrated residential and commercial development and is frequently exposed to a range of natural hazards, which include flooding, storm effects, and coastal erosion. In response, the U.S. Geological Survey (USGS) is conducting a national assessment of coastal change hazards. One component of this research effort, the National Assessment of Shoreline Change Project, documents changes in shoreline position as a proxy for coastal change. Shoreline position is an easily understood...
thumbnail
In 2012, US Geological Survey (USGS) and National Oceanic & Atmospheric Administration (NOAA) embarked on an ambitious project to digitize surficial seafloor data from existing National Ocean Service (NOS) smooth sheets in the Gulf of Alaska including numerous bays bordering the Gulf. USGS and NOAA are using the data for the nation-wide usSEABED ( http://walrus.wr.usgs.gov/usseabed) project that seeks to compile and unify existing seafloor characterization point data into GIS-friendly data using the dbSEABED program (Jenkins, 1997; Reid and others, 2005; Buczkowski and others, 2006; Reid and others, 2006) and for the North Pacific Research Board’s Gulf of Alaska Integrated Ecosystems Research Program (NPRB, GOA-IERP,...
As part of the USGS's California State Waters Mapping Project, a 50-m grid of sediment thickness for the seafloor within the 3-nautical mile limit between Point Sur and Point Arguello was generated from seismic-reflection data collected between 2008 and 2014, and supplemented with geologic structure (fault and fold) information following the methodology of Wong (2012). Water depths determined from bathymetry data were added to the sediment thickness data to provide information on the depth to base of the post-LGM unit. Reference Cited: Wong, F. L., Phillips, E.L., Johnson, S.Y., and Sliter, R.W., 2012, Modeling of depth to base of Last Glacial Maximum and seafloor sediment thickness for the California State Waters...
thumbnail
Model experiments that attempt to simulate climates of the past serve to identify both similarities and differences between two climate states and, when compared with simulations run by other models and with geological data, to identify model-specific biases. Uncertainties associated with both the data and the models must be considered in such an exercise. The most recent period of sustained global warmth similar to what is projected for the near future occurred about 3.3–3.0 million years ago, during the Pliocene epoch. Here, we present Pliocene sea surface temperature data, newly characterized in terms of level of confidence.
thumbnail
These data are part of the effort to map geologic substrates of the Stellwagen Bank National Marine Sanctuary (SBNMS) region off Boston, Massachusetts. The overall goal is to develop high-resolution (1:25,000) interpretive maps, based on multibeam sonar data and seabed sampling, showing surficial geology and seabed sediment dynamics. The data were collected in collaboration with the Stellwagen Bank National Marine Sanctuary and will aid research on the ecology of fish and invertebrate species that inhabit the region. Sediment samples were collected aboard the Sanctuary's research vessel, R/V Auk at 679 locations on and near Stellwagen Bank using a customized Van Veen grab sampler integrated into the USGS SEABed...


map background search result map search result map Digital seafloor character data of the Gulf of Alaska from historical National Ocean Service (NOS) smooth sheets National Assessment of Shoreline Change: A GIS compilation of Updated Vector Shorelines and Associated Shoreline Change Data for the Gulf of Mexico Coast Bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996, 1998, and 2000 Photogrammetric digital surface models and orthoimagery for the continuous coastline, Wales to Platinum, Alaska, segment B: Teller to Nome Shotpoint navigation at a 500-shot interval for chirp seismic-reflection data collected in 2016 by the U.S. Geological Survey off Town Neck Beach Sandwich, Massachusetts during field activity 2016-017-FA Revised PRISM3 Pliocene Sea Surface Temperature Estimates Location and analyses of sediment samples collected on Stellwagen Bank off Boston, Massachusetts from November 5, 2013 to April 30, 2019 on U.S. Geological Survey field activities Shotpoint navigation at a 500-shot interval for chirp seismic-reflection data collected in 2016 by the U.S. Geological Survey off Town Neck Beach Sandwich, Massachusetts during field activity 2016-017-FA Bathymetry and backscatter intensity of the sea floor of the Historic Area Remediation Site in 1996, 1998, and 2000 Location and analyses of sediment samples collected on Stellwagen Bank off Boston, Massachusetts from November 5, 2013 to April 30, 2019 on U.S. Geological Survey field activities Photogrammetric digital surface models and orthoimagery for the continuous coastline, Wales to Platinum, Alaska, segment B: Teller to Nome National Assessment of Shoreline Change: A GIS compilation of Updated Vector Shorelines and Associated Shoreline Change Data for the Gulf of Mexico Coast Digital seafloor character data of the Gulf of Alaska from historical National Ocean Service (NOS) smooth sheets Revised PRISM3 Pliocene Sea Surface Temperature Estimates