GEOLOGY OF THE COAST SYSTEM OF MOUNTAINS. 19 
the Gavilan Range on the south. This fault is interesting for several reasons: it lies 
approximately in the axis of the geosyncline of the Bay of Monterey; it is transverse 
to the San Andreas Rift and intersects it; and it is near the place where the surface rup- 
ture of the San Andreas fault ceased on April 18, 1906. 
South of the Bay of Monterey, one of the dominant structural lines of the Coast Ranges 
is the Santa Lucia fault, at the base of the Santa Lucia Range on the border of Salinas 
Valley. It is traceable from the vicinity of Bradley to the Bay of Monterey and it is 
probably the chief factor in determining the course of the Salinas-Valley and the steep 
easterly front of the Santa Lucia Range. Near its southern end, the Santa Lucia fault 
is paralleled on the southwest by another fault which probably determined to some 
extent the course of the valley of San Antonio River. Farther south a fault parallels 
the last two, between Dove and Templeton; and to the southwest of this lies the much 
longer fault hich passes close to San Luis Obispo, extending from near San Simeon to 
the drainage of the Santa Ynez. 
The northeastern flank of the San Emidio Range, at the southern end of the great 
valley, is with little question a fault-scarp. The same may be said of the north flank 
of the Santa Ynez Range and the south flank of the Santa Monica Range. The San 
Gabriel fault, which bounds the range of that name on the south, branches from the San 
Andreas fault near San Bernardino and follows the base of the range with an east-west 
trend. Beyond Pasadena it bends slightly to the north and extends thru to the coast 
in the vicinity of Carpenteria. Near Pasadena a branch fault leaves it, with a north- 
westerly strike, on the northeast side of the Verdugo Mountains. Southeast of Los 
Angeles, the most notable faults are the San Jacinto and Elsinore faults, both of which 
have very pronounced scarps. There are, however, several others. All the faults in 
this region have a northwest-southeast strike, and are thus in contrast ta the system of 
faults extending from Point Conception to the Colorado Desert along the Sierra Madre, 
in which the dominant trend is east and west. 
The foregoing summary enumeration of the more important faults at present known 
in the Coast System of mountains makes it clear that the San Andreas fault, upon which 
movement took place on April 18, 1906, is not a singular or unique feature fe the struc- 
ture of these mountains. It is only one of many faults, on all of which in time past 
there have occurred many differential movements, each productive of. an earthquake. 
Map No. 1, upon which the above faults are represented, indicates other faults in Cali- 
fornia, Nevada and Oregon at present known to geologists.‘ Perhaps the most 
interesting of these, from the present point of view, is the fault at the eastern base of 
the Sierra Nevada, upon a portion of which the movement took place that caused the 
earthquake of 1872. The map may be regarded as a preliminary attempt to bring 
together, in cartographic form, our knowledge of the position of faults in this region. 
A full discussion of these features, with references to the literature bearing upon them, 
would be out of place here, altho their occurrence suggests seismic possibilities. 
GEOMORPHIC FEATURES. 
Certain of the geomorphic features of the Coast Ranges, particularly as regards their 
margins, have necessarily been alluded to in the discussion of the structure. It is pro- 
posed here to describe quite briefly the salient characters of the relief, in their relation 
to the structure. 
The Coast Ranges in general, between the coast and the Great Valley and north of Santa 
Barbara Channel, comprize a series of ridges and intervening valleys of mature aspect. 


1 In compiling the data for the representation of the faults of California, free use has been made of 
information kindly supplied by Messrs. H. W. Turner, W. Lindgren, W. C. Mendenhall, H. W. Fairbanks, 
J. 8. Diller, F. M. Anderson, R. Arnold, J. C. Branner, G. D. Louderback, and O. H. Hershey. 
