Lawson.] 



The Upper Kern Basin. 



343 



was not, as has just been shown, a fault dislocating the Chagoopa 

 Plateau, but it might well have been a rift fissure. Such a 

 structure once established would continue to control the future 

 process of erosion so long as the stream bed was above the base 

 level, and it has not yet reached base level. Along such a rift 

 there might be a recurrence of the tendency to open, which tend- 

 ency woidd undoubtedly result in the engulfment of wedges 

 formed by the intersection of auxiliary slip planes with the main 

 rift. In this sense the canon of the Kern is both a rift valley 

 and an erosional trough. Probably only a minor proportion of 

 the cross-section of the canon is to be accounted for by the pro- 

 cess of engulfment of graben wedges or slabs, and the most of it 

 has been removed by the ordinary processes of stream erosion. 



THE KERN LAKES. 



In the foregoing description of the features of Kern Canon 

 frequent reference has been made to Upper and Lower Kern 

 Lakes. These have been referred to, moreover, as occupying 

 intervals between kernbuts, and the reader may possibly have 

 gained the impression that these lakes are due to damming by 

 the formation of the kernbuts. This is not the case. The lakes 

 are quite recent features of the canon, and owe their origin to 

 special causes, some account of which may now be given. Lower 

 Lake is the older of the two. It is about half a mile in diameter 

 and is separated from Kern River by a levee of sand and silt on its 

 east side, the stream following a straight course at the base of 

 the east wall of the canon. The outlet of the lake is by a small 

 rivulet which traverses this levee at its southern end. Prior to 

 the completion of the levee, the lake had been partially silted up 

 by sediment from the river, and since it has been shut off from 

 the river, the silting process has been continued by the minor 

 drainage from the west side of the canon, and by lake vegitation; 

 so that a considerable fraction of its area is swamp. The dam 

 which holds up the lake is the debris of the large rock-slide, 

 already referred to, which fell from the east wall of the canon 

 immediately opposite a kernbut about three miles below the 

 mouth of Coyote Creek. This dam is a chaotic aggregation of 

 huge blocks of granite through which the stream makes its way 



