2'2S The American Geologist. • October, 1807 
former land connection that no question can be raised in re- 
gard to it. It might be supposed, however, that the islands 
were formed simply by a sinking of the region now occupied 
by the Santa Barbara channel. This view is not supported 
by the conditions existing since the early Pleistocene; no 
differential movements of such magnitude are known to have 
occurred. The recent downward movement has been general, 
affecting both mainland and islands. Tiiere are numerous 
facts, however, which point to the elevation of the coast as a 
whole, at the time when the mammoth flourished, which will 
be taken up in their proper place. 
The deepest point on the submarine ridge connecting the 
Santa Barbara islands with the mainland is 1 25 fathoms or 
about 750 feet. This connecting ridge extends eastward 
toward Point Hueneme, near the mouth of the Santa Clara 
river. In all probability the post-Pliocene elevation was more 
than 1,000 feet. An elevation of 1,300 feet would connect the 
western-most of the islands with point Conception. The 
centre of the channel forms a depressed basin with a depth 
of about 2,100 feet. 
The Submarine Phifeau. The work of professor George 
Davidson* has shown that the coast of California, as well as 
of Oregon and Lower California, is bordered by a submarine 
bench or plateau of varying width. Along the coast of north- 
ern California it is quite narrow, being not much over 10 
miles across. From Point Arena southward it begins to 
widen, sweeping just outside of the Farralones islands, and 
then narrowing again as the bay of Monterey is approached. 
Opposite the Golden Gate it has a width of about 32 miles. 
Otf the coast of California the plateau of the Pacific has 
a depth which varies from 2,000 to 2,400 fathoms. The 
marginal plateau generally slopes very gradually out to the 
region of the 100 fathom curve, when it takes on the much 
steeper descent to deeper portions of the plateau or abyssal 
depths. Opposite the high and rugged Santa Lucia mount- 
ains the 100 fathom curve runs four to six miles from the 
shore, and from that the descent is rapid until a distance out 
of 57 miles, when it reaches a depth of 2,000 fathoms. Far- 
*Hydrographic charts of the U. S. Coast and Geodetic Survey. Sub- 
merged Valleys of the Coast of California, Proc. Cal. Acad, of Scien- 
ces, 3rd series, vol. i. 
