234 llie American Geologist. October. i897 
both sides of the bay dij) under it. The form of tlie depres- 
sion does not however indicate a simple syncline, for the de- 
scent is gradual both on the north and south to the 100 fath- 
om line below which it changes quite abruptly becoming very 
steep. The submarine valley proper on a section between San- 
ta Cruz and Monterey is not over 4 miles wide, descending to 
400 fathoms, while the main bay is 24 miles across. Accord- 
ing to Lawson the sedimentary rocks dip westward at Pajaro, 
and taking in connection with this, the submerged northwest 
prolongation of Point Pinos, an east and west structural de- 
pression is rendered improbable. Granting that the broad fea- 
tures of Monterey bay are due to folded Miocene strata, that 
is are structural, the portion of the submarine trench extend- 
ing up close to the shore near the mouth of the Salinas river 
must lie in strata more recent than the Miocene. In all prob- 
ability the rocks of this age are much more than 1000 feet be- 
low the surface, which about the mouth of the river consists 
of Pleistocene and Pliocene strata. The Salinas well some 
distance back from the mouth of the river did not apparently 
reach through the Pleistocene at a depth of 1300 feet. 
The recent subsidence at the Golden Gate forming a new 
outlet for the Great Valley accords very well with the ab- 
sence of any marine valley at that point and supports the 
view of professor Le Conte tliat the outlet was at one time in- 
to the bay of Monterey. 
Several submarine valleys* have been detected oif the coast 
of northern California. These lie near together south of cape 
Mendocino and are quite remarkable in several ways. The 
distance between them is 8-10 miles and thej cut across the 
submarine plateau at depths varying from 400 to 520 fathoms. 
Only one of them lies opposite a river's mouth, the coast gen- 
erally rising very steeply to hights of 4000 feet a little over 
two miles from shore. The submarine valleys extend in re- 
markably close to the shore, one having a depth of 25 fatl.ioms 
less than one third of a mile out. Another reached to a point 
where the water is not more than 15 fathoms deep. They all 
lie very nearly perpendicularly to the coast line. The sub- 
merged plateau between them has a gentle and even slope 
down to the 100 fathorfi contour at a distance of 8 to 10 miles 
*Proc. Cal. Acad, of Sci., 1886-1887. 
