14 



The Ocean 



The first scientific interpretation of the topographical chart of the ocean bottom 

 taken in conjunction with a contour map of the land areas of the Earth was a general 

 investigation of the relationships of heights and depths on the surface of the Earth crust. 

 This was a purely statistical analysis of the variations of the surface of the solid crust 

 about an average value, the mean crust level. If the whole of the solid crust of the Earth 

 were levelled off" to give a single solid sphere, the mean level of the solid surface would 

 be 2440 m below the present sea-level. The level of the sea itself would then be 

 about 260 m above the present level, that is, the solid crust would be covered by a 

 layer of water 2700 m thick (Kossinna, 1921). It would be expected that the fre- 

 quence of occurrence of individual heights and depths was entirely random. The mean 

 crust level (taking the present sea-level as zero: —2440 m) should occur most fre- 

 quently, and the frequencies of individual heights and depths around this should 

 form a probability curve. In these chance cavities the water would collect as oceans 

 and the formation of the oceans would then offer no problems, since they would 

 obviously form in the deepest depressions of the crust. 



The statistical distribution of the heights and depths of the Earth crust has, however, 

 led to the striking result that the frequency in no way approaches a Gaussian-probabi- 

 lity curve. On the contrary, there are two height-intervals which occur with high fre- 

 quency while the other, less frequent, intervals group themselves around these two 

 culmination points as two probability curves (Fig. 8, Table 2). 



6000 



4000 



2000 



2000 



E 4000 



6000 



! 12 16 



Frequency percentoge 



20 



24 



Fig. 8. Frequency distribution of different height and depth intervals over the entire surface 



of the Earth. 



The two maximal frequencies lie at the height-interval of 0-1000 m and at a depth 

 interval of 4000-5000 m; nearly 45% of the entire surface of the Earth falls within 

 these two intervals, while only 10% falls on the other eleven steps. It is especially 

 noticeable that the mean crust level of —2440 m (depth interval —2000 m to —3000 m) 

 occurs infrequently, and is indeed very near the minimum between the two maxima. 



