chains,
making a sudden turn nearly east and west, or almost at a right angle.
The Sierra Nevada also bends around towards the west and meets the
Coast Ranges, and hence results a confusion of topographical structure
and of geological formation. The highest elevation of the belt, that of
Mount San Antonio in the San Gabriel range, is here attained.
South
ot Los Angeles the coast line returns nearly to its former northwest
and southeast course, and the ranges appear to come into general
conformity with it; but there is apparently much irregularity in the
details, of which, in fact, but little information is extant.
General Geological Structure.—As
a general rule the rocks of the belt of the Coast Ranges are altered
and unaltered sandstones, shales and slates of cretaceous and tertiary
formations, with more or less limestone. The sedimentary beds have been
metamorphosed over wide areas, crushed and folded to form the various
ranges. In some regions volcanic rocks appear in large quantities.
Granite occurs here and there, but almost always in small masses,
except where the Sierra Nevada makes its influence felt. It forms an
important feature, however, in some of the chains south of Monterey
Bay, and forms the axis of the Santa Monica range, which differs in
this respect from the other Coast Ranges. Other rocks are almost
unknown, except where the Coast Ranges and the Sierra come into close
contact.
Metamorphism—The
metamorphism of the rocks is principally chemical, and is very
prevalent throughout the belt, often to such an extent that it is
extremely difficult, if not impossible, to distinguish between rocks
of the most opposite nature, such as the eruptive and the sedimentary.
Especially noticeable is the enormous extent of change of slates into
serpentine, in connection with which broken jaspery rocks, also a
product of the alteration of slates, very commonly occur. These
combinations of serpentines and jaspers are important to the
