SUBMARINE VALLEYS ON THE PACIFIC COAST. 267 



are remarkably steep. The 100 fathom curve of the valley 

 comes close between the general 30 fathom curve on the 

 north and south, where they are one-third of a mile apart. 



The opening of this valley through the edge of the 100 

 fathom plateau is 520 fathoms deep, and is only six miles S. 

 62^ W. from Point Gorda. The barrier of coast line at the 

 head of this valley is over 2,000 feet high. 



Suhmai^ine VaUey Til. Between Point Gorda and Cape 

 Mendocino there is a second submarine valley, a little 

 nearer to the cape. It comes in from the westward, but 

 does not indent the 20 fathom line along the shore, but the 

 depth of 100 fathoms in the valley is only one-third of a 

 mile outside the regular 25 fathom coast line, and lies five 

 miles S. by E. from Cape Mendocino light house. 



The 450 fathom sounding in the entrance to the valley is 

 only six and a half miles SW. by S. from the cape, and this 

 valley is comparatively wide. Its north side is formed by a 

 30 fathom submarine plateau extending ^\q miles from the 

 cape. This valley heads under the great mountain mass, 

 rising behind Cape Mendocino and reaching 3,400 feet ele- 

 vation. 



The bottom of the valley is green mud, and yet in two 

 places, at depths of 320 fathoms, broken shells were brought 

 up with gravel. Both slopes of the valley are green mud 

 up to about 30 or 35 fathoms, when the bottom changes to 

 fine gray sand. 



Between the two submarine valleys of Point Gorda (II.) 

 and Cape Mendocino (HI.)) the submarine ridge carries 50 

 fathoms out for four and a quarter miles from shore; the 

 bottom is green mud outside of 35 to 40 fathoms, with fine 

 gray sand inside. 



Northward of the Cape Mendocino submarine valley, the 

 irregular bottom off Cape Mendocino, marked by Blunt's 

 reef, stretches well to the westward of the usual coast 



