NATURAL SALT PANS 355 



best known. (\\^alther-6i : /Sq.) This is a low-lying coastal area, 

 flooded during the southwest monsoon period in some parts to the 

 depth of I meter. The Rann is the true salt plane; it covers an 

 area 300 km. long and 100 km. broad. It merges into flat planes 

 free from vegetation, the so-called Put, and is surrounded and 

 diversified by the sand-dune region, the so-called Thurr. Here the 

 dunes are 25 to 130 meters high, with flat areas often carrying 

 lakes up to 20 meters in depth, and this region is inhabited chiefly 

 by foxes, jackals, wolves, rats, snakes, etc. In the region of the 

 Rann proper animal life, as well as plant life, is exceedingly scarce. 

 The smooth, flat surface of the Rann is composed of sandy clay, 

 which is constantly kept moist by the included salt. The shallow 

 pools scattered about on its surface are covered in winter by crusts 

 of pure salt, generally only about 10 cm., but occasionally over a 

 meter in thickness. 



The Nile delta, too, is characterized by a large number of salinas 

 or natural salt pans. These extend along the coast from Abu Sir 

 to Sheik Zayed, and owe their salt to the flooding from the Medi- 

 terranean and the rapid evaporation due to the desert climate of the 

 coast. The salt is often covered by wandering sand dunes, which 

 when they reach a great thickness become filled through efflores- 

 cence with crystals of gypsum 3-5 cm. long. These unite into 

 heads i to 4 meters broad and from 0.5 to i meter in thickness. 



On the borders of the Red Sea are a number of salinas. One, 

 west of Amfila (Hanfela) Bay on the Abyssinian border, lies below 

 sea-level, and is surrounded by a wall of gypsum. The streams 

 flowing from the East Abyssinian Mountains into this depression 

 evaporate, adding their contribution to the saline deposits. At 

 Allolebod, on the southern coast of the Red Sea, the deposits in the 

 natural pans show regular interstratification by layers of gypsum, 

 similar to the annual rings of the Stassfurt salt. These layers mark 

 the periodic inundation of the salt pans. Though extensive, these 

 salt deposits can in no wise be compared with those of past geologic 

 periods. (Grabau-19.) 



Evaporation of Cut-offs from the Sea. 



When, in an arid region a portion of an indentation of the sea 

 is cut ofif, by tectonic movements, by delta deposits, or otherwise, 

 the waters thus separated may evaporate, leaving a salt sea or salina 

 in which the salt of the original water body becomes concentrated. 

 The Salton-sink region in the Lower Colorado P.asin of California 

 is an example of such a cut-off. The delta built by the Colorado 



