To an observer in space the planet Earth would appear as a globe 

 largely covered by water. The continental gardens and lesser islands 

 rising out of the sea occupy only 29 per cent of the total surface 

 area of the planet and are surrounded by water with an average 

 depth ranging from two to three miles. Throughout geological 

 time there have been many dramatic changes in the level of the sea 

 in relation to the land. At times a substantial portion of the oceans 

 has been locked up as ice, and coast lines everywhere have been 

 altered. At other times subsidence has drowned coastal areas and 

 cities — sometimes overnight. Today about half of the three hundred 

 major ports and coastal cities built between 3000 b. c. and the fall 

 of the Roman Empire are submerged and many are being excavated 

 by underwater archaeologists. 



Man's exploration of the oceans began long before recorded 

 history. Curiosity must have been one of the motives but the main 

 inducements were the search for food and wealth. During the fif- 

 teenth and sixteenth centuries the search for trade routes to the East 

 and the discovery of new lands were the main driving forces. Soon 

 after James Cook's famous voyages in the late eighteenth century 

 most of the great geographical pu22les of the oceans had been 

 solved. In the following century oceanography was to receive its 

 greatest stimulus from science, which sponsored expeditions like 

 the three-year voyage around the world of the research ship 

 H. M. S. Challenger. Today the scientific exploration of the oceans 

 is being carried out by many nations. Like the earlier explorers, 

 the scientist-explorers of the twentieth century continue to search 

 the sea for food, but in addition they are looking for ways to tap 

 the vast mineral wealth and to harness the energy locked up in 

 the oceans; but perhaps more important are the basic studies 

 that are refining our knowledge of the great chain of life in the seas, 

 the currents, the action of waves and tides, and geological and 

 geophysical aspects of the sea floor. 



The shadow relief maps appearing throughout this book stress 

 the features of the ocean floor rather than those of the land. In 

 most of the maps, therefore, the coloring of the land has been 

 subdued or treated in such a way that the reader's eye is directed 

 to the sea areas. Wherever physical configuration of the ocean floor 

 is important, relief coloring has been used: the lighter blues de- 

 noting shallower water and the darker blues deeper water. In many 

 maps color is used to provide additional information. For example, 

 a range of red tones on the currents map (pages 204-05) shows the 

 surface temperature of the sea. On another map a sequence of colors 

 ranging from yellow to green denotes the relative fertility of the 

 sea. Keys accompanying all such maps explain the meanings of 

 the colors. 



About this Book 



The world map on pages 6 and 7 shows the k 

 main features of the ocean floor - the great ' 

 abyssal plains, mountain ranges, ridges, and 

 continental sheli/es. The coloring of the 

 water ranges from light blue (shallow water) 

 to deep blue (deeper water) . 



Wolfgang Foges 

 Roy A. Gallant 

 Shirley Carpenter 

 Hans Erni 

 Judy Hannington 



EDITORIAL DIRECTOR 

 EDITORIAL ADVISER 

 GEOGRAPHICAL DIRECTOR 

 ART DIRECTOR 

 ART EDITOR 



