Lawson.] 



The Upper Kern Basin. 



M9 



Glacial Modification of Kern Canon. — The question as to the 

 extent to which the trunk glacier of the Kern modified the canon 

 in which it flowed may now be briefly considered. As has been 

 already pointed out, the path of the glacier in the canon falls 

 into two parts, an upper part, in which the Kern has been 

 engaged in vertical corrasion since the retreat of the ice, and a 

 lower part in which it has been engaged in aggradation. Part of 

 this aggradation, may, however, have been accomplished while 

 the ice was still in the upper part of the canon in the late stages 

 of its retreat. But as the meadows of the canon floor show no 

 evidence of dissection and are still subject to flooding by the 

 stream which winds through them, it may safely be inferred that 

 the aggradation is still in progress. This portion of the stream 

 then is below grade for the load that it carries, and as the main 

 terminal moraine is well dissected, the latter cannot be regarded 

 as a cause of the retardation of the stream, especially as it flows 

 on bedrock a short distance below the moraine. Now the stream 

 below the limit of glaciation is far above grade, and it seems, 

 therefore, probable that the entire course of the stream in pre- 

 glacial time was above grade. If this be the case, then it is evi- 

 dent that the portion of the canon now aggraded represents an 

 over-deepening of the canon floor by glacial scour, a process 

 which has been exemplified in many glacial troughs, such as in 

 some of the lochs of Scotland and fjords of Norway. The depth 

 of this aggradation is not known, but it may well have been 

 sufficient to have left a lake for a time after the retreat of the 

 ice. Both the degraded and aggraded portions of the glaciated 

 canon are U-shaped in profile, but the most perfect U-shaped pro- 

 file is in the former, and is true of the rocky floor and sides of 

 the canon. The U-shaped effect of the aggraded portion is 

 largely due to the talus slopes at the base of the canon walls. 

 If the rocky bottom of the canon beneath the meadow floor be 

 also U-shaped, as is very probable, then the depth of the aggra- 

 dation accumulation may be not more than a hundred feet. 



The width of Kern Canon, below the Kern-Kaweah River, 

 does not appear to have been appreciably increased by the occupa- 

 tion of the ice. This is practically proven by the following con- 

 sideration. The depth of the ice in the canon averaged probably 



