24 
SANTA MARTA OTL DISTRICT, CALIFORNIA. 
Where steep hills descend toward the coast there is almost without 
exception a coastal terrace starting at the top of the sea cliff, which, 
as a rule, ranges in height from a few feet to more than 50 feet above 
the water. Most of these terraces extend up to an elevation greater 
than 200 feet. Some of them have left traces at a height of 300 feet 
or more, and others continue perfect to this altitude or even higher. 
GENERAL TOPOGRAPHIC FEATURES. 
The point of especial interest in the topography of the central region 
between the two bounding ranges is its characteristic reflection of the 
structure of the formations, whereas in the mountains, as has been 
noted, the topographic development has been less in accordance with 
the lines of structure. An anticline in the central region is apt to be 
coincident with a ridge, as, for example, in the long ridge of the 
Purisima Hills, which lies close to the axis of a broad anticline. 
Moreover, some of the larger valleys mark the synclinal axes of the 
broad lines of structure—a statement illustrated by the Santa Ynez 
Valley in parts and by its structural, although not actual, continua¬ 
tion in the Santa Rita Valley. It is also exemplified bv the upper por¬ 
tion of the Los Alamos Valley and by Harris Canyon. These topo¬ 
graphic features may be accounted for by the facts that the main 
movements in these hill ranges have been gentle as compared with 
those in the older mountain masses, that the disturbances giving 
them form have been comparatively recent, and that deformation 
has not gone so very far. Wherever there are low areas of rolling 
hills it is almost sure to be found that a syncline or plunging fold has 
given rise to structural depressions in which deposits of soft sand pro¬ 
ducing low topographic forms have been laid down. 
The character of the different formations shows its influence on the 
topography. The areas of serpentine with associated Franciscan rocks 
have irregular broken surfaces with many outcrops and usually an old, 
well-worn appearance. The dominantly sandstone and shale terranes 
described under the headings “pre-Monterey rocks” and “Vaqueros, 
Sespe, and Tejon formations, undifferentiated,” do not give rise to a 
very distinctive topography. They form a succession of ridges and 
V-shaped canyons of moderate relief and comparative regularity. In 
many places the truncated edges of the tilted strata form steep, rough 
strike slopes. The Monterey shale produces the forms of highest relief 
in this region, as well as forms of low relief, according to the amount 
of folding that has taken place in it and to its hardness. The 
brittle shale closely folded gives rise to sharp ridges, many of them 
serrate, with steep, rocky flanks. Ridges of highly tilted shale are 
shown in PI. VI, B (p. 46). The lower folds produce hills of gentle 
incline and long unbroken ridges, in places parallel with the strike 
