B. THE HYDROSPHERE. 



CHAPTER HI. 



MORPHOLOGY AND SUBDIVISIONS OF THE HYDROSPHERE. 



The hydrosphere consists of the oceans and their prolongations 

 into the land blocks, the lakes, the rivers, and the ground water. 

 The oceans and their extensions into the land blocks constitute the 

 marine portion of the hydrosphere ; the lakes, rivers, and ground 

 waters constitute the non-marine or continental portion. In the 

 present chapter their morphological characteristics will be discussed, 

 and an attempt will be made to outline a natural classification of the 

 various subdivisions, based primarily on origin. 



A. THE MARINE DIVISION OF THE HYDROSPHERE. 



REGIONAL SUBDIVISIONS OF THE SEA. The classifica- 

 tion of oceans and minor subdivisions of the sea has attracted the 

 interest of geographers from the earliest times. Many and varying 

 systems of classification have been proposed, based on size, form, 

 position with reference to the land, composition, origin, etc. Otto 

 Kriimmel (23 :^p) has published a very comprehensive system of 

 the seas, in which he recognizes as primary divisions : ( i ) The 

 independent, and, (2) the dependent types; the former comprising 

 the oceans, the latter the mediterraneans — subdivided into (a) inter- 

 continental, and (b) intracontinental mediterraneans — and the mar- 

 ginal seas. Added to these are: (3) the gulfs or bays, and (4) the 

 straits. Two other subdivisions are made on the basis of ingression 

 of the sea into existing depressions, with the subsidence of the land, 

 forming ingression seas, gulfs, or straits ; or, on the partial breaking 

 down of the surface and sinking of fault blocks, permitting the sea 

 to enter the land and forming tectonic seas, gulfs, or straits. 



In a natural subdivision of the sea into basins, its relation to the 

 continental blocks must be considered of primary importance, since 



99 



