Smith.] 



Islands of Southern California. 



'93 



northern slopes of the island. On the small hachured map (U. S. 

 C. & G. S.) of Santa Rosa, the appearance of this half of the island 

 is that of a platform dissected by numerous streams flowing in 

 comparatively open valleys. It would seem that these platform-like 

 areas could be ascribed only to marine action, either deposition or 

 abrasion or both. No very decided indications of terraces, how- 

 ever, appear on the map for this part of the island, except close to 

 the northern shore. At the western extremity and at various 

 points along the northern shore a narrow elevated terrace appears, 

 of the marine origin of which there can be little doubt. The main 

 ridge descends gradually from the island's crest to the northwest, 

 and along its course are found several nearly level stretches. At 

 about 1,000 feet the ridge is nearly level for over a mile; the inter- 

 val between the 540- and 580-foot contours, along the ridge, is more 

 than half a mile, while that between the 420- and 440-foot contours, 

 near the western extremity of the island, is a mile and a half. The 

 forms near this western extremity are probably more or less modi- 

 fied by drifting sand, as indicated on the small map. 



Santa Rosa faces the mainland, which is distant only about 

 thirty miles, so that the waves on the landward side have not the 

 sweep that they have in the case of San Nicolas, distant about 

 sixty miles from that part of the coast which it faces. In the case 

 of both islands, the waves from the open sea can strike the northern 

 coast only at a considerable angle. Judging from the submarine 

 contours, the greatest cutting in the case of San Nicolas is on the 

 northwestern extremity, where a low angle of slope is presented 

 toward the open sea. The same is true of San Miguel Island, to 

 the west of Santa Rosa ; and the cutting in the case of Santa Rosa 

 would doubtless be more pronounced were it not that the western 

 end of the island is somewhat protected from wave action by San 

 Miguel. 



Santa Rosa has one broad and open bay, which is not con- 

 nected with the present stream valleys of the island. There are no 

 bays at the mouths of the present stream valleys, comparable in size 

 to the harbors at Avalon and at the Isthmus on Santa Catalina, nut 

 this is apparently due to a lack of valleys of sufficient size and devel- 

 opment. The same thing is true of Santa Cruz Island. Small bays 



