688 W. ,C. ALDEX PRE-WISCONSIN GLACIAL DRIFT IX MONTANA 



There are in the cirques at the heads of the valleys, high up on the 

 flanks of the mountains in the heart of the Lewis Eange, one hundred or 

 more existing glaciers, ranging in size from those a few square rods in 

 extent to ice fields of 2 or 3 miles area. Besides the cirques in which 

 these glaciers lie, there are a multitude of glacial amphitheaters, in 

 many of which are beautiful lakes, but in which glaciers do not now 

 exist. These cirques are among the most wonderful phenomena of the 

 park. From these cirques broad-bottomed, steep-walled, U-shaped val- 

 leys extend to the mountain front, showing in their contours and in the 

 deposits of drift which they contain the effects of a former much more 

 numerous existence and much greater extension of the valley glaciers. 

 Numerous trunk glaciers, fed by a multitude of tributary glaciers, ex- 

 tended eastward and westward to and beyond the mountain front. The 

 deposits of those extending out on the plains to the east of the range 

 have been described by Mr. F. H. H. Calhoun in professional paper 

 number 50 of the United States Greological Survey, entitled "The Mon- 

 tana Lobe of the Keewatin Ice-sheet.^^ Ice discharging from the moun- 

 tain valleys tributary to Two Medicine Eiver is described as having 

 coalesced and spread over the plain as "a large piedmont glacier which 

 extended about 50 miles from the main divide and which in its widest 

 part was over 30 miles across.^ This is referred to as the "Blackfoot 

 Glacier," a somewhat infelicitous designation, inasmuch as the largest 

 •of the existing glaciers in the park, but 10 miles distant from the head 

 of Two Medicine Valley at the nearest point, bears the name "Black- 

 feet." A better name for the extinct glacier, which headed principally 

 in valleys tributary to Two Medicine Eiver, would be the "Two Medicine 

 Glacier." Perhaps I may be pardoned if on account of this conflict in 

 nomenclature I make this substitution. At the head of Lower Two 

 Medicine Lake the ice in this valley had a thickness of about 1,000 feet. 



Ice in the valleys of the north and south forks of Cut Bank Creek, the 

 next stream north of the Two Medicine, coalesced several miles from 

 the mountain front forming the Cut Bank glacier, which extended about 

 18 miles from the Continental Divide. Two small lobes of the glacier 

 spilled northward through sags in the crest of Milk Eiver Eidge^ into 



3 Loc. cit, p. 18. 



* There seems to be some confusion of usage of names applied to the several ridges of 

 Cretaceous sandstone and shale east of the mountain front. Mr. Calhoun, in his paper, 

 refers to the ridge east of Lower Saint Mary Lake as "Milk River Ridge," and to the 

 ridge north of Lower Two Medicine Lake as "Cntbank Ridge." On the topographic 

 maps, however, the name "Saint Mary Ridge" is applied to the ridge east of Lower Saint 

 Mary Lake, and the name "Milk River Ridge" to the ridge north of North Fork of Cut- 

 bank Creek. This latter usage, which appears to be the common one, will be followed 

 in the present paper. The name "Cut Bank Ridge" will be applied to the ridge between 



