CHAPTER XIV 

 THE COASTAL TERRACES 



Along the entire coast of Peru are upraised and dissected ter- 

 races of marine origin. They extend from sea level to 1,500 feet 

 above it, and are best displayed north of Mollendo and in the des- 

 ert south of Payta. The following discussion relates to that por- 

 tion of the coast between Mollendo and Camana. 



At the time of the development of the coastal terraces the land 

 was in a state of temporary equilibrium, for the terraces were 

 cut to a mature stage as indicated by the following facts: (1) the 

 terraces have great width — from one to five and more miles; (2) 

 their inner border is straight, or, where curves exist, they are 

 broad and regular; (3) the terrace tops are planed off smoothly 

 so that they now have an even gradient and an almost total ab- 

 sence of rock stacks or unreduced spurs; (1) the mature slopes 

 of the Coast Range, strikingly uniform in gradient and stage of 

 development (Fig. 148), are perfectly organized with respect to 

 the inner edge of the terrace. They descend gradually to the ter- 

 race margin, showing that they were graded with respect to sea 

 level when the sea stood at the inner edge of the highest terrace. 



From the composition and even distribution of the thick-bed- 

 ded Tertiary deposits of the desert east of the Coast Range, it is 

 concluded that the precipitation of Tertiary time was greater than 

 that of today (see p. 261). Therefore, if the present major streams 

 reach the sea, it may also be concluded that those of an earlier 

 period reached the sea, provided the topography indicates the per- 

 fect adjustment of streams to structure. Lacustrine sediments 

 are absent throughout the Tertiary section. Such through-flowing 

 streams, discharging on a stable coast, would also have mature 

 valleys as a consequence of long uninterrupted erosion at a fixed 

 level. The Majes river must have cut through the Coast Range 



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