En 
278 Part III. Chapter 3. 
That such oscillations have occurred is proved by the record which geo- 
logists have determined. During the post-Miocene it is probable that all the 
islands then differentiated were mountainous masses belonging to the main- 
land. Judging from their topography, and the apparent genetic relationships 
of those of the northern group, the forms then existing probably included all 
the present islands, except San Nicolas and San Clemente. The latter appear 
not to have been elevated until, the close of the post-Miocene erosion period, 
or early in the Pliocene depression. The post-Miocene elevation of the coast 
was followed by the Pliocene depression during which the sea stood for a long 
time some 1500 feet above its present level and the coast had the aspect of 
an archipelago. During this depression at first Santa Catalina, San Clemente, 
San Pedro Hill, Santa Cruz and Santa Rosa all existed as islands, or as in 
the case of Santa Cruz and Santa Catalina, as two or more small islands. 
Then as now, Santa Cruz was probably the highest, if not the largest of the 
existing islands. This depression was followed by a post-Pliocene elevation. 
This elevation was perhaps sufficient to connect the northern islands with the 
mainland, none of the southern islands have had such connection since the, 
post-Miocene period of erosion. The most recent movement of the coast, 8 
indicated by drowned valleys and submarine features, is a comparatively slight 
depression. Paleontologic evidence is not wanting for in the pliocene rocks 
on the peninsula of San Francisco are found cones of Pinus insignis (P. radial 
Monterey pine), a tree which at the present time grows only at Monterey ) 
With this radical transformation in the physiography of the coast, there 
have doubtless been very important changes in the climate, and in this fact 
is to be found, the explanation of certain remarkable and anomalous featufe® 
in the distribution of the plants ofthe coast. As a consequence of the general 
uplift of the coast and southern California, the physiography of the country 
has been radically changed in the most recent geologic times. The ge 
below the sea or influenced by delta deposits was tenanted in the great centrä 
valley and along the slopes of the elevated mountains of southern a 
with plants derived from the south. These at the present day form the desef 
and chaparral vegetation of the summits of the lower hills which were once 
beneath water and on the mountain flanks, while the higher mountain summ i 
which existed as islands during the last submergence are clothed with a 
vegetation which during the Pliocene depression existed nearly at sea-level 
With increasing aridity the lower limits of the mountain forests was deter 
mined by available moisture. A tentative arrangement of the vegetation ele- 
ments in southern California according to their age is herewith given: 
1) FAIRBANKS, W. H.: The Age of the California coast Ranges. American Geologist unleze 
1896: 271. LAwsoNn, ANDREW C,: The post-Pliocene Diastrophism of the Coast of ge 
California. Bulletin Department Geology University of California I: 115—160. 6; 
LesLieE: The Great Valley of California do. Univ, of California I: 371—428- SMITH; z 
TANGIER: A topographic Study of the Islands of southern California do. Univ. of California 
179— 230. 
FEDER 
