xvin THE CRATERS OF THE RIFT VALLEY 227 



and Suswa ; and the Aberdare mountains with the 

 high peak of Kinangop (13,214 ft.). 



The Rift Valley differs from the common kind of 

 valley in the character of its lateral boundaries. In 

 valleys, as a rule, the sides slope gradually from the 



Giant Lobelias (L. Deckenii). 



high ground to the low, but in this valley the sides 

 are, in places, as steep and abrupt as those of a grave : 

 indeed the traveller may suddenly come to the edge of 

 one of these steep walls and run a risk of tumbling over. 

 Steep boundaries of this kind are called " escarpments " ; 



Q 2 



