Summary for Field Activity Number 1978-023-FA

Alternate Leg ID: CI 7-78-1

Area of Operations: Mid-Atlantic outer continental shelf and slope, United States, North America, North Atlantic

Dates: August 18, 1978 to September 04, 1978

Objectives: Study slumping or mass movements of sediments on the continental slope using high-resolution geophysical profiling gear.

Type of Activity: Seismic profiling

Information to be derived: Sea floor map
Morphology

Summary: Slumping and mass downslope sediment movement occurs widely over the continental slope at small scale (small thickness, small displacement) as well as large scale. Individual slump features, although readily identifiable as large masses on individual seismic profiles, may have small lateral extent or may change considerably in their form and location on the slope within the 0.5 nautical mile spacing of our profiles. Continental slope topography cannot be described by dip (offshelf) profiles. Strike (longslope) lines show much rougher topography on the upper continental slope than a series of dip lines would imply. Rough and smooth upper slope topography give the same appearance on dip lines. Sidescan sonar data may show a grain of small (several meter) features paralleling the continental slope. Airgun: 2050 km; Minisparker: 2100 km; 3.5 kHz: 2100 km; Sidescan: 22 km.

USGS Project Number: EA

Contact: Jim Robb (jrobb@usgs.gov)