77?^ Ocean 



Fig. 2. Percentage distribution of water and land areas in five degree zones. 



The arrangement of the continents outlines the irregular distribution of the sea. 

 The sea fills the depressions between the continents as far as its volume allows. On 

 closer inspection a division into three major oceans can be recognized: the Atlantic, 

 the Pacific and the Indian Ocean. They are all connected with each other, forming a 

 continuous ocean belt in the higher latitudes of the Southern Hemisphere. This can 

 be seen very clearly on Steinhauer's star projection centred on the south pole. Here 

 the Atlantic and the Indian Oceans appear as very large and extended bays radiating 

 out from the circumpolar Southern Ocean (Fig. 3). 



The main boundaries of the three oceans are fixed in the first place by the conti- 

 nents. Conventional boundaries are necessary only to the south of Australia, South 

 America and Africa where distinct morphological boundaries are missing. These have 

 been fixed by international agreement (Intern. Hydrogr. Bureau, Monaco, 1937; 

 WiJST, 1939). 



The three major oceans are subdivided by the continental coast lines which in some 

 places are remarkably irregular. There is a particularly marked contrast between the 

 open ocean and the seas enclosed between mainland and groups of islands. The sea 

 areas which are separated from the ocean and project to a greater or lesser extent into 

 the continents are denoted adjacent seas, and according to the degree of separation 

 from the open ocean they may be either marginal or mediterranean seas. The demarca- 

 tion from the ocean is usually topographical. The more important adjacent seas are 

 listed in Table 4 (see p. 1 7), together with the area, the mean and maximum depths of the 



