268 



lloor, underl.vin.ii the sens l)eyond the limits of la-esent national Jurisdiction, he- 

 fore events take an irreversihle course. 



The dark oceans were the womb of life : from the protecting oceans life 

 emerged. We still bear in our bodies — in our itlood, in the salty bitterness of our 

 tears — the marks of this remote past. Retracing the past, man, the present 

 dominator of the emeiged earth, is now returning to the ocean depths. His peiic- 

 (ration of the deep <'ould mark the lieginning of the end for man, and indeed 

 for life as we know it on this eartii : it could also be a unique opportunity to lay 

 solid foundations for a peaceful and increasingly prosperous future for all 

 peoples. 



The air is the atmosphere of our planet : the seas and the oceans are the atmo.s- 

 phere of the submerged land which constitutes more tlian tive-sevenths of the 

 area of tliis earth. The sea has been used as a means of connnunication in ijeace 

 aud war for thousands of years : it.s living rt^sources, plants and fish have long 

 been exploited: and around the use of the surface and upper layei"s of the seas 

 a complex of international law has developed, but the depths of the oceans and 

 the ocean floor were of little interest until little more than a hundred years ago 

 when the question of laying a trans-Atlantic cable came to the fore. It was at 

 that time that the first scientific deep-sea surveys were undertaken. Sub.'^equent- 

 ly, the invention of the echo-sounder enaliled scientists to o])tain much more 

 precise and detailed information on the sJiape of the bottom of the seas and 

 oceans than had been possible by using the previous method of the weighted 

 line. Ocean floor photography and deep submergence vessels with near-bottom 

 capability now enable us to acquii-e an ever-increasing store of Icnowledge about 

 the sea-beds and the abyss, although we nuist remember that vast areas still 

 remain to be mapped. 



It may be useful at this stage to give a general idea of the geophysical fea- 

 tures, known resources of the ocean floor and present technological capability 

 to exploit them. 



The land underlying the seas and the oceans constitutes nearly three quarters 

 of the land area of this earth. It is commonly divided into the continental shelf, 

 the continental slope and the abyss. 



The continental shelf can be defined as that area of the sea or ocean floor 

 between the mean low water line and that sharp change in the inclination of 

 the floor that marks the inner edge of the continental slope. The sharp change 

 in inclination from about one-eighth of one degree to more than three degrees, 

 occurs at varying depths, usually around the 130 to 150 metre contour line. The 

 width of the shelf ranges from less than one mile to up to 800 miles. Continental 

 shelves, frequently scarred by deep canyons, can be generally characterized as 

 the geological continuation of adjacent land areas of wliicli they are the 

 submerged extension. 



The continental slope, usually from ten to twenty miles wide, extends from 

 the outer edge of the continental shelf to the abyss or ocean floor. The inclination 

 of the slope varies widely from as little as three degrees to over forty-five 

 degrees : slopes of twenty-five degrees are connnon. 



The abyss or ocean floor appears to be a rolling plain from 3,300 to about 

 5,500 meters below the surface of the sea : it is scarred by deep gorges called 

 trenches and studded with sea mounts and guyots. The mean depth of the sxiper- 

 jacent waters is 3.800 metres. More than seventy-five per cent of the ocean floor 

 lies at a depth of less than 5,000 metres. 



Ocean basins are frequently separated by great submarine mountain ranges. 

 a few of the peaks of which sometimes rise above the water. The greatest 

 mountain ranges on earth are not on any continent, but in the sea. The Mid- 

 Atlantic ridge extends the entire length of the Atlantic, spanning one-third of 

 the circumference of the globe and frequently rising 3,500 metres above the 

 ocean floor. The Mid-Oceanic ridge extensively mapped during the years 1959- 

 1965 by the International Indian Ocean Expedition, organized by the Inter- 

 national Council of Scientific Unions, cui'ves in a great arc, in places 1.500 

 miles broad, from the Arabian peninsula to the Crozet Islands, rising occasion- 

 ally to 5,000 metres above the abyss, yet even its highest peaks miss the surface. 



The floors of the seas and oceans are covered by sediments: terrigenous com- 

 paratively near the coast, pelagic farther from shore. Pelagic sediments are 

 called clays when they contain less than 30 per cent of organic renuiius. and 

 oozes when they contain more than 30 per cent of these remains. The oozes in 

 turn are divided into two main groups : calcareous oozes and siliceous oozes. 

 Oozes and clays are the dominant sediments of the ocean floor: however, other 



