CLIMATE AND TERRESTRIAL DEPOSITS 187 



the entire eastern shore, terminating abruptly in the lofty and precipitous cliffs, 

 which for a thousand miles constitute the predominant feature of this coast. 



In addition to the characters described above, there may be mentioned as 

 among the more important features of these plains a series of deep transverse 

 valleys that extend from the Andes to the Atlantic. These are all true valleys 

 of erosion, and for the most part they are still occupied by considerable streams.^ 



The prominence of these cliffs indicates the extent to which the 

 waves have planed inland, beginning a new and lower cut upon each 

 uplift of the land. The inadequacy of subaerial denudation in this 

 semiarid climate, w^ith less' than ten inches annual rainfall, is indicated 

 by the presence, except in the few river valleys, of the shingle formation 

 left by the retreat of the sea and the fact that the large river valleys 

 are such as derive their waters from tlie Andes. In more rainy regions 

 the almost level and porous deposits left upon a retreat of the sea also 

 resist rain erosion in the interstream areas for considerable periods 

 of time, but in such regions there is much local drainage and the 

 development of a network of valleys which upon a pronounced uplift 

 permit a rapid erosion. 



Along the southwestern coast of Australia for a distance of seven 

 hundred miles the land is terminated by a line of cliffs more than 

 five hundred feet in height unbroken by any stream course and facing 

 a shallow sea which in the Great Australian Bight extends to one 

 hundred and fifty miles from land before attaining a depth of one 

 hundred fathoms. The rainfall is here not over ten inches per 

 year. Such lofty and unbroken walls indicating the dominance of 

 marine over subaerial erosion, it would seem impossible to match in 

 more generously watered regions of theworld; such cliffs as those of 

 Norway and Scotland being cut through on the contrary by valleys of 

 erosion besides forming the front of mountain regions and therefore 

 not necessarily implying a wide horizontal cut for their formation. 



The preceding discussion has turned upon the slowness of subaerial 

 erosion in arid climates when acting upon more or less horizontal and 

 debris-mantled formations. An indication of the relative slowness 

 of deflation may also be obtained from southern California and its 

 adjacent islands by noting the remarkable freshness of the naked 

 granite rocks and the sharpness of the post-Pliocene elevated sea- 



I J. B. Hatcher, Princeton Patagonia Expeditions, Vol. I, pp. 214, 215, 1903. 



