1 24 University of California. [Vol. t . 



little of its terraced effect. Even where the canons are close together, 

 the ridges between them are not sharp, as in the case of older 

 topography, where a different effect, due to the intersection in ridge 

 crests of the slopes of adjoining canons, is produced. The plateau 

 effect has not yet been destroyed, and the topography of the hill, 

 as a whole, is yet in its juvenescence. 



Geological Structure. — San Pedro Hill is composed of the white, 

 siliceous shale which characterizes the Miocene of the coast, 

 together with limestone. Much of the shale is similar to the rocks 

 of the Monterey series at Carmelo Bay.* Certain beds at Redondo 

 beach are rich in siliceous organisms. The dip of the beds at the 

 east end of the hill is westward at an angle of about 22 , and gener- 

 ally over the hill the strata appear to be inclined at angles for the most 

 part not exceeding 30 . Systematic observations were not made for 

 the direction of the dip. The only part of the hill which is not com- 

 posed of" these Miocene rocks is the lower northern and eastern 

 flanks, where Pliocene and later formations have been deposited 

 around its base. These Pliocene formations are rich in fossils, and 

 have attracted the attention of geologists more than the hill itself, 

 so that the Pliocene of San Pedro Harbor is the only Tertiary 

 formation which has been recorded as occurring here. 



Evidence of Uplift. — To most geological readers, what has been 

 said of the physiography of San Pedro Hill is in itself sufficient 

 evidence of recent uplift, the inference being that the terraces, 

 which are such striking features of the topography, are sea terraces, 

 and represent ancient ocean strands. That such is the origin of 

 these, and of similar terraces along the coast, has been denied by 

 Mr. George Davidson, of the United States Coast and Geodetic 

 Survey. Mr. Davidson has had exceptionally good opportunities 

 for observation. Although not a professional geologist, his remarks 

 and criticisms are worthy of consideration, and geological science 

 is indebted to him for his keen interest in the terraces as topographic 

 forms, and to the Coast and Geodetic Survey for the many excellent 

 bits of topographic maps which it has given us, of those portions of 

 the coast where the terraces are well displayed. Mr. Davidson not 

 only rejects the idea of the terraces having been developed by the 



*Cf. this Bulletin, Vol. I, p. 22. 



