638 K. PUMPELLY EVOLUTION OF OASES AND CIVILIZATIONS 



Asia. Later, during the middle Tertiary, this connection was broken, 

 leaving a great interior sea called the Sarmatic, which once extended 

 from Austria to beyond the Aral. 



In the progressive development of land and climate, during Pliocene 

 or late Tertiary time, this sea in turn broke up into separate land-locked 

 basins of fresh and brackish water, the deposits and faunae of which are 

 designated as belonging to the Pontic stage. 



Deserts 



Tracts with no outlet 

 seaward 



Figure 1.— Arid Regions and closed Basins of Asia. 

 From Elisee Reclus "The Earth and its Inhabitants." 



In these changes we see the evolution of central Asia as an interior 

 region. Differentiated from the periphery of the continent by moun- 

 tains that intercepted the moisture from the ocean on the south, and 

 otherwise climatically at a disadvantage on account of its geographical 

 relation to the laws of atmospheric circulation, this vast region entered 

 upon an independent course of development. 



