GEOLOGY OF PERU ADAMS. 421 



RAISED BEACHES. 



The action of the sea in cutting cliffs may be well observed along 

 the coast of the northern coastal plains, where the Tertiary forma- 

 tions at many places rise in sheer bluffs. The same process has been 

 in operation at other places on the coast where elevation has taken 

 place and the cutting action of the sea is displayed in a succession of 

 marine terraces. These are especiallA?^ noticeable on the coast between 

 Pisco and Lomas, where the Pisco formation displays approximately 

 ten distinct terraces rising to a height of perhaps 1,000 feet. Along 



Fig. 10. — Section sbowiug: marine cut terraces at the moutli of the Ocofia River. 



the southern part of the Peruvian coast in front of the range of coast 

 hills where the rivers have cut their canyons through, there are ter- 

 races in the igneous rocks which constitute the hills and also in the 

 remnants of what were once delta formations of these streams. The 

 terraces at the mouth of the Ocoila River, as seen by the writer and 

 measured with an aneroid, are represented in the following sketch 

 (fig. 10). The upj)er terrace at Ocoiia is the highest one which was 

 found on the coast. 



Terr oca cut in igrieous roe/^ 



/OSOft. 



Fig. 11. — Section showing marine cut terraces at the mouth of the Ilo River. (Compare 



fig. 8.) 



Tlie railroad station, Tambo near Mollendo, on the Southern Rail- 

 way, has an elevation of 1,000 feet and is situated on the north side of 

 the River Tambo near its mouth, on an extensive terrace which must 

 have attracted the attention of many travelers, although its origin is 

 not explained in any scientific article which has come to the writer's 

 notice. 



The terraces south of the Ilo River, near its mouth, are indicated in 

 the above sketch (fig. 11). 



