USGS Geological Research Activities with U.S. Minerals Management Service

Sea-Floor Mapping

Over the past century, managers, decision makers, and scientific researchers in coastal and marine environments faced a critical issue; an almost complete lack of accurate sea-floor base maps. Accurate base maps are essential for any geological study. For land-based studies, aerial photographs, USGS 7.5-minute quadrangle maps, and satellite imagery are commonly used as base maps. Many marine base maps of sea floor have been constructed in the past, however, the depth and navigational accuracies of these maps have been questionable.

The USGS and its partners are using high-resolution, multibeam systems and advanced data processing techniques to systematically map the sea floor and sediments of the U.S. continental shelf, with emphasis in areas of critical economic or biologic importance. The USGS Pacific Seafloor Mapping project uses state-of-the-art digital multibeam systems to systematically map the sea floor. With these types of efforts, the marine navigational accuracy has now approached 1 meter and the depth resolution 50 centimeters.

The two types of data collected through this project include high quality bathymetry (sea-floor depth) and quantitative backscatter (data that can provide insight into the geologic makeup of the sea floor and used to make shaded-relief maps).

The high-resolAugust 23, 2007ne habitat biologists, State, Federal, and local authorities to generate geological and biological information and to set regulations on sea-floor uses. Among it many applications are:

• Predicting underlying sea-floor facies;
• Calculating volume of material needed to be excavated for large ships to pass safely;
• Predicting seafloor stability in tectonically active areas with faults and underwater landslides;
• Studying historical seafloor change;
• Mapping the distribution of offshore dredge disposal sites; and
• Using as real-time ground control for remotely operated vehicles (ROV), allowing the operator and scientists to view the ROV relative to a large area of the ocean floor.

In 2002, a collaborative effort between the USGS, MMS, and the Flower Garden Banks National Marine Sanctuary (FGBNMS) has resulted in mapping additional areas of the northwestern Gulf of Mexico to produce high-resolution (5-m spatial resolution) multibeam echosounder images of the area. Both MMS and FGBNMS funded the mapping effort. The USGS organized the ship and multibeam systems through a cooperative agreement between the USGS and the University of New Brunswick. USGS personnel were responsible for the overall cruise including the final data processing and digital map products.

The USGS has collected about 45 days of high-resolution multibeam data in both the northeastern and northwestern Gulf of Mexico. To date, less than 5 percent of the northwestern Gulf of Mexico has been mapped and possibly as much as 10 percent of the northeastern Gulf of Mexico. All of the data are available on the web (http://walrus.wr.usgs.gov/pacmaps). USGS has provided the MMS with Open-File Report CD-ROM's containing all the data.

 

 

 

 

Sea-floor images by the USGS Coastal and Marine Geology Program and cooperators:

Region mapped	Page in USGS Circular 1199	Web site or reference
Western United States
Pacific sea floor (Hawaiian Islands, San Diego, Los Angeles)	p.22	http://walrus.wr.usgs.gov/pacmaps/; Dartnell and Gardner (1999)
San Francisco Bay	p.10	http://terraweb.wr.usgs.gov/TRS/projects/SFBaySonar/; http://sfbay.wr.usgs.gov/access/mapping/multibeam/; Dartnell and Gardner (1999)
Monterey Bay National Marine Sanctuary	p.13	http://terraweb.wr.usgs.gov/TRS/projects/MontereySonar/
Lake Tahoe	--	http://blt.wr.usgs.gov; Gardner and others (2000)
Gulf of Mexico and Southeastern United States
Gulf of Mexico	p.21	http://coastal.er.usgs.gov/east_gulf/
Lake Pontchartrain	p.10	http://coastal.er.usgs.gov/pontchartrain/
Florida Keys	p.13	Lidz and other (1997)
West Florida	p.20	Briere and others (2000)
Oculina Bank off east-central Florida	p.13	Scanlon and others (1999)
Northeastern United States
New York, New Jersey Bight	p.7	Schwab and others (1997)
Long Island Sound	p.8	Poppe and others (1997, 1998a,b); Twichell and others (1997, 1998); Knebel and others (1999)
Stellwagen Bank National Marine Sanctuary	p.13	Valentine and others (2000)
Massachusetts Bay and Boston Harbor	p. 7, 24	Bothner and others (1992); Butman and Lindsay (2000)