THE BAHAMA ISLANDS 9 



The irregular outline of the Bahama plateau is one of its most significant 

 characteristics. In the northeast portion this is particularly well marked on 

 account of the separation of the Little and Great Bahama Banks by Providence 

 Channel and also by the embayments known as " Tongue-of-the-Ocean " and 

 " Exuma Sound." These embayments dissect the Great Bahama Bank so that 

 it resembles a letter S and admits the deep waters of the ocean into the very 

 heart of the plateau. The southeastern half of the platform does not appear 

 so irregular in outline; but this is due to the fact that passages such as 

 Crooked Island, Caicos, Turks, and Silver Bank have taken the place of 

 embayments; or, in other words, that erosion has destroyed whatever con- 

 necting banks formerly existed and now allows the ocean to pass unobstructed 

 between the individual island groups. 



There is another feature which marks the northwestern portion of 

 the plateau strongly from the southeastern, and that is the greater pre- 

 ponderance of shallow water in the former and of deep water in the latter. 

 Throughout the northwestern. Little and Great Bahama Banks, with the 

 islands which they carry on their surfaces, stand out in marked contrast 

 to the more insignificant banks of the southeastern half, which form groups 

 independent of one another. This contrast between the two divisions of the 

 Bahama platform conveys the impression that the surface as a whole slopes 

 toward the southeast. This impression is increased from the fact that the 

 Silver and Navidad Banks, situated in the extreme south, are devoid of islands. 

 But one should not too quickly conclude from this that the platform is 

 actually depressed toward the southeast. On the contrary the facts would seem 

 to indicate that the difference in depths of water are due not so much to 

 deformation as to differential erosion and that the southeastern half has 

 suifered relatively more than the northwestern. 



Surface. — The surface of the Bahama platform is divisible into a deep- 

 water and a shallow-water facies. The former, as has just been said, is more ex- 

 tensively developed throughout the southeastern half of the region, while the 

 latter dominates the northwestern. Concerning the physical features of the 

 surface, the methods employed in the exploration of the deep-water facies have 

 not been sufficiently delicate to reveal more than salient features. Judging from 

 the data procuied from soundings, its surface appears to be flat and practi- 

 cally featureless except where it rises abruptly to form banks and pass over 

 into the shallow-water facies. More is known regarding the shallow- water 

 facies, for it lies so near the surface of the ocean that it can be distinctlv 



