136 BULLETIN UNIVERSITY OF MONTANA 



stronger throw on the southern end. This resulted in a much larger slip on 

 the southern end of the range than on the northern. In fact the slight 

 slip on the north together with the erosion by weathering and valley gla- 

 ciers has resulted in a complete termination of this range, per se, near the 

 University of Montana Biological Station as noted above. The slip must 

 have been several thousand feet at the southern end as the peaks near 

 the St. Ignatius mission are 7,000 feet higher than the plain below. The 

 weathering following the elevation of this range has left the escarpment 

 in jagged and precipitous cliffs making the range one marked by most 

 picturesque scenery. 



With the most superficial study only, it is suggested that the range 

 noted above, the Kootenais, N. E. of the Mission range and forming the 

 Tjoundary of Flathead valley, was probably formed by a similar fault. The 

 range of foothills which forms an irregular boundary of the Mission valley 

 and of Flathead lake on the west, reaches westward to a considerable size 

 and shows the strata once continuus with those of the Mission range. They 

 ■were evidently depressed coincident with the tilting of the Mission which 

 movements, together with the erosion in the trench like valley formed, 

 "■'^t "hout the long valley extending 100 miles north and south. 



Such a valley likewise is the Bitter Root valley, though the peculiar 

 feature of this larger valley under discussion is that while the other val- 

 leys of similar history in the state show plainly by their drainage that ero- 

 sion by streams and rivers has played an important part in the cutting and 

 enlarging of the depression along the fault plane, this one by its peculiar 

 termination at the Jocko hills on the south and by its entire lack of evi- 

 dences of stream courses from Flathead lake to the south end gives indi- 

 cations of a different history. More detailed study may show that the 

 valley was once occupied by a large stream, or that the drainage, unlike 

 that of to-day, was to the northward instead of southward. 



The Jocko hills may have been faulted or raised after the valley 

 erosion had been finished. I have never been able to find any record 

 of excavations in the valley bottoms by which could be learned the depth 

 of the soil and gravel to the rock. 



It has been noted above that the Mission valley has a general eleva- 

 tion of from 100 to 250 feet above the lake while the Flathead valley is 

 much more regular in its surface and is but slightly elevated above tha 

 lake. These two valleys are of different history in so far as the bottoms 

 are concerned. 



Flathead valley plains show clearly that the soil is made almost en- 

 tirely of sediments deposited in the still waters of the lake. This ac- 

 counts for the level character of the plains. Little if any glacial de- 

 posit has been formed in this valley. Some is found in the rounded 

 hills near the mouth of Swan river and along the eastern border of the 

 valley below Kalispell. These are undoubtedly closely connected with 

 the glacier deposits found nearer Swan river valley. The lake which filled 

 the valley ecrtainly much higher than at present evidently receded rapidly 

 as I have been unable to find any bench marks or terraces on the hill- 

 sides. However it apparently receded more slowly after it had reached 

 the level of the Flathead valley sediments as several old stream courses 

 are plainly discernible between the town of Kalispell and the lake. 



