<P> Continental shelves in the Atlantic are wide off Newfoundland, southern-most South America, and north - eastern Europe . In the western Atlantic carbonate platforms dominate large areas, for example the Blake Plateau and Bermuda Rise . The Atlantic is surrounded by passive margins except at a few locations where active margins form deep trenches: the Puerto Rico Trench (8,414 m or 27,605 ft maximum depth) in the western Pacific and South Sandwich Trench (8,264 m or 27,113 ft) in the South Atlantic . There are numerous submarine canyons off north - eastern North America, western Europe, and north - western Africa . Some of these canyons extend along the continental rises and farther into the abyssal plains as deep - sea channels . </P> <P> In 1922 a historic moment in cartography and oceanography occurred . The USS Stewart used a Navy Sonic Depth Finder to draw a continuous map across the bed of the Atlantic . This involved little guesswork because the idea of sonar is straight forward with pulses being sent from the vessel, which bounce off the ocean floor, then return to the vessel . The deep ocean floor is thought to be fairly flat with occasional deeps, abyssal plains, trenches, seamounts, basins, plateaus, canyons, and some guyots . Various shelves along the margins of the continents constitute about 11% of the bottom topography with few deep channels cut across the continental rise . </P> <P> The mean depth between 60 ° N and 60 ° S is 3,730 m (12,240 ft), or close to the average for the global ocean, with a modal depth between 4,000 and 5,000 m (13,000 and 16,000 ft). </P> <P> In the South Atlantic the Walvis Ridge and Rio Grande Rise form barriers to ocean currents . The Laurentian Abyss is found off the eastern coast of Canada . </P>

Which one of the following is the cold current of south atlantic ocean