39. How far into the ocean can one "see" the effect of a river? 



By using an echo sounder as eyes, one can "see" the effect of rivers 

 in the submarine canyons that extend seaward for hundreds of miles 

 from the mouths of some rivers. 



Hudson RivEW 



A submarine canyon 4 miles wide and 240 feet deep extends from 

 the mouth of the Ganges River into the Bay of Bengal for a distance of 

 more than 1,000 miles. The Congo Canyon has been traced for 145 

 miles to a depth of 7,500 feet. 



Off the Hudson River a canyon extends 200 miles across the con- 

 tinental shelf. This canyon was surveyed by the Woods Hole Oceano- 

 graphic Institution vessel ATLANTIS (cover illustration). 



The continental shelf along the Pacific Coast of the United States is 

 narrow and its submarine canyons are deep and steep-sided. The Mon- 

 terey Canyon, off California, is sometimes compared with the Grand 

 Canyon. 



The origin of submarine canyons is still under dispute. There is 

 speculation that channels may have been cut by rivers while the land 



41 



