THE RED SEA AND THE ARCHIPELAGO OF 

 DAHLAK 



There is a number of theories as to the geological origin of 

 the Red Sea; I will briefly quote two of them. 



The first theory is that the Red Sea has its origin in 

 enormous faults in the Eocene strata and the flooding of 

 these depressions with water from the north, that is, from the 

 Tethys Sea. Following a later interruption of the link with 

 the Tethys Sea, the Red Sea was subject, in the Miocene 

 period, to intensive evaporation. Besides destroying all forms 

 of life, because of the high increase in the salinity of the sea, 

 this process of evaporation left great deposits of saline rock 

 which can still be found on certain stretches of the coasts. 

 Towards the end of the Pliocene period the Red Sea became 

 connected with the Indian Ocean and forms of life passed 

 from one sea to the other. 



The second theory, by Sewel, maintains that after a drop 

 in marine levels caused by the expansion of the glaciers of 

 the Pleistocene period, the communication between the Red 

 Sea and the Indian Ocean may have been interrupted by the 

 appearance of a bar between the two seas. Since the Red 

 Sea was already separated from the Tethys Sea it was 

 transformed into a salt lake and practically all forms of life 

 vanished. With the recession of the glaciers in the second 

 phase of the Ice Age and the raising of the sea level, com- 

 munication between the two seas was re-established. Fauna 

 then passed into the Red Sea. (After the cutting of the Suez 

 Canal in 1869, it was ascertained that some forms of life 



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