SIERRAN VALLEYS OF THE KLAMATH REGION l6l 



in width, drained by an insignificant creek through a narrow 

 valley. From the description, it is probably a short section of 

 the bottom of a Neocene valley, the gravel filling of which has 

 been cleaned out by erosion. It is also probable that at or in 

 the vicinity of the present Hyampom valley the old Trinity river 

 was joined by the Hay Fork river. 



It is apparent that the deformation of the Neocene surface in 

 the western part of Trinity county took the form of a broad arch. 

 It is believed that this extended north through Siskiyou county, 

 across the courses of the Salmon and Klamath rivers. It is 

 niarked by the deep, narrow, rocky gorges of all the streams 

 which cross it. These gorges invariably have the gulch type, so 

 characteristic of Pleistocene erosion in the Klamath region, and 

 their comparative youthfulness is beyond dispute. 



Hav Fork stream, between the Hay Fork and Hyampom 

 Neocene valleys, is said to flow for miles through a deep rocky 

 gorge whose relative narrowness is not satisfactorily explained 

 by the resistant properties of the formations trenched. New river, 

 a northern tributary of Trinity river, has trenched a deep valley 

 into the supposed arch. The New river country, although not 

 high and rugged as the Sierra Costa mountains, is so extremely 

 brokefi as to be almost inaccessible. An effort was made to con- 

 struct an especially well-graded trail along New river, yet in places 

 it climbs nearly a thousand feet above the stream to get around a 

 rockv point. The valley is characterized by immense landslides, 

 which form rough terraces and at one place supply enough level 

 land for a farm. These landslides are the result of the very 

 rapid down-cutting of the bottom of the valley. The phenomena 

 witnessed throughout this region tell of the newness of the cycle 

 of erosion. All the valleys are of the same gulch type as those 

 of Trinity Mountain, which are known to post-date the uplift of 

 the Neocene deposits. In the latter region, the vertical ele- 

 ment of the erosion hardly exceeded 1,500 feet, but in the lower 

 Trinity and New river country, it was not less than 3,000 feet. 



The gorge of the Salmon river between Bennett's and its 

 mouth seems to belong to the same category as those just men- 

 tioned. Perhaps the most magnificent example of the class is 



