CHAPTER XIII. 



GEOLOGY OF THE CORDILLERAS. 



Chain known by the name of oordilleras. — Direction. — Repetitions of the chain. — Passes. — Character, of the ca.ion pass 

 AND SAN GOUGOxo.— Altitude OF the passes. — Conglomerate of the slopes. — Strata in the oajon pass. — Cause of the 

 DIP of the strata. — Different aspect of the Cordilleras viewed from the western and eastern sides. — A.xial rocks of 

 THE CORDILLERAS.— Structure at warker's and the ca.ion. — The sedimentary strata on the west slopes. — Period of 

 elevation OF the chain.- San emilio mountain. — Geology op the district surrounding. — The most elevated land in 



southern CALIFORNIA. PeRU RIVER. CaSoNS OF, THROUGH QBANITIO ROOK. SEGREGATION OF MINERALS OF THE GRANITE. 



Ce-stek PLAIN. — Sandstones of, conformable to the Cordilleras but not to the sierra Nevada. — Relative modern 



APPEARANCE OF THE FORMER RANGE. — CONTINUITY OP SAN EMILIO WITH POINT PINOS RANGE. — RaDIATION OF THE CHAINS FROM 

 SAN EMILIO DISTRICT. — SaNTA BARBARA CHAIN ELEVATED INDEPENDENT OF THE CORJILLERAS. — DIRECTION OF THE VOLCANIC 

 FISSURES OF THE COAST RANGES. 



Under this term is included the mountain range which extends from the point of junction 

 of the Sierra Nevada and the coast ranges to the Mexican boundary line, and thence southward 

 into Lower California, of which it forms the spine. It is not, by any means, a continuous 

 chain, but a series of disjointed masses running in a nearly parallel direction, the intervals in 

 the chain being the passes from California proper into the desert. 



The direction of the Cordilleras is uniform. If a line be extended from San Emilio mountain 

 in a direction south 50° east to parallel 34°, it will be found to cover the great mass of the 

 range lying between these two points, the southern termination being the great mountain San 

 Bernardino. The length of this range is about 150 miles. 



Temecula mountain, in 33° 30', commences another range, which extends south 45° east, 

 and passes into the peninsula of Lower California. The observed length of this range was 80 

 miles. The continuity of these two ranges is preserved by the San Jacinto mountain, which 

 lies between San Bernardino and Temecula mountains. 



The passes which occur in these two ranges, leading from the coast into the Great Basin and 

 the Colorado desert, are — 



1. San Francisquito pass^ (also called Turner's pass.) 



2. New pass. 



3. Cajon pass. 



4. San Gorgoiio pass. 



5. Warner's pass. 



Of these, only passes 1, 3 and 5 will be noticed here, as they alone were subjects of observa- 

 tion. It may be doubted if passes 1 and 2 are true arrests of the upheaving power ; they might 

 be more properly considered as alterations of denudation and fracture, produced in a continuous 

 range by actions occurring long posterior to the elevation ; while in the Cajon pass there is a 

 wide separation of several miles between the lofty mountain masses of Kikal Mungo and the 

 range prolonged northwest from San Bernardino, a separation so wide that, looking from the 

 plain at any point south of the pass — as from the Mormon town — a wide passage can be plainly 

 discerned between the ranges. The ranges are really connected by the stratified sandstones of 



