Technological advances have provided geologists with new research tools to more effectively study the sea floor. By integrating bathymetric data and both long-range and deep-towed side scan data with observations and samples obtained from a deep diving submersible (each with increasing scales of resolution) we can identify sea-floor processes and consider their history and recently. Although the U.S. Atlantic continental slope and rise north of Cape Hatteras can, in general, be characterized as being dissected by numerous submarine canyons, the comparison of deep towed data from three areas of the margin shows similarities and differences in the details of the sea-floor morphology. The canyons are interpreted to be at different stages of development. Density type flows, bottom current activity, and mass wasting are among the processes which are thought to be important within the canyons on the slope and rise. Deep-towed side scan and submersible data are important not only in determining the sea-floor processes that occur in the slope and rise environment, but also in determining the temporal and special variability of the processes which control the sediment sources for the construction of the rise.
The U.S. Atlantic continental slope from Georges Bank to Cape Hatteras is dissected by numerous downslope-trending canyons (Fig. 1). Bathymetric surveys in the 1930's defined this dissected morphology for the first time Since that time as technology has advanced, so has our, understanding of sea-floor morphology and the processes that shaped it.
With improved navigation and narrow-beam echo sounders (1 1/2° to 3° half-angle beam width) in comparison to wide-beam echo sounders (30° half angle beam width), detailed surveys were the first steps to refining our knowledge of the continental slope and upper rise morphology (Fig. 2). Such data showed that not only was the slope dissected, but that the sea-floor gradient was highly variable, from less than 5° to greater than 26°, over short distances4. Both the irregularity of the sea floor and the steepness of the slopes produce hyperbolic echo that make the interpretation of echo-sounding profiles collected at the sea surface difficult. The detailed topography of the sea floor in the deep water of the continental slope and rise cannot be precisely resolved from the sea surface by acoustic means.
Another step toward defining the sea-floor morphology was the development of systems that provide a real view of the sea floor, not just point values along a track line. Such systems include Sea Beam multi-beam mapping, GLORIA long-range sidescan, and Sea MARC II which has both side scan and mapping capability? With these systems, maps of the sea floor can be constructed without interpolating between point values along widely spaced grids of track lines.
