. The Atlantic continental shelf and slope, a program for study. Continental shelf. it ranges from less than 15 km off Florida to 500 km in tlie Gulf of Maine. The total area is about 510,000 sq km, of which nearly half is in the Gulf of Maine (for simplicity considered here as Continental Shelf). The surface of the Con- tinental Shelf is a plain made somewhat irregular by glacial features in the Gulf of Maine by nu- merous submarine valleys, most of which only indent the shelf-break, by submerged wave-cut cliffs along most of its length, and by sand waves on Georges Bank and elsewhere (fig. 1
. The Atlantic continental shelf and slope, a program for study. Continental shelf. it ranges from less than 15 km off Florida to 500 km in tlie Gulf of Maine. The total area is about 510,000 sq km, of which nearly half is in the Gulf of Maine (for simplicity considered here as Continental Shelf). The surface of the Con- tinental Shelf is a plain made somewhat irregular by glacial features in the Gulf of Maine by nu- merous submarine valleys, most of which only indent the shelf-break, by submerged wave-cut cliffs along most of its length, and by sand waves on Georges Bank and elsewhere (fig. 1). Beyond the shelf break is a complex array of of continental slope, marginal plateau, and con- tinental rise. The continental slope is steep (averaging 5°), and it descends to between 900 and 3,000 m. The average width is about 50 km and the area is about 150,000 sq km. Along most of its length, the continental slope is cut by sub- marine canyons. Benches, believed to have been produced by outcrops of resistant strata, occur along part of its length. At the base of the continental slope is a broad apron, the continental rise. Much of the shal- lower part may be of structural origin, but the deeper part is probably a fan of debris deposited by turbidity currents. At its toe is an abyssal plain 5,000 to 5,500 m deep. The average width of the continental slope, marginal plateau, and continental rise between the shelf-break and the 5,000-m contour is 550 km, and the total area is about 1,400,000 sq km. Contour charts of the Continental Shelf and slope are being prepared from most existing soundings; the charts will be contoured at 10-m intervals on the shelf and at 200-m intervals on the slope. The results of new surveys by the Coast and Geodetic Survey will be incor- porated as they become available. In addition, sounding lines will be run about 18 km apart with the Precision Depth Recorder (which re- cords in meters) aboard Gosnoldduring the course of sampling operations and i
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