86 I. C. RUSSELL — HANGING VALLEYS 



required to excavate it. This case does not stand alone, and there are 

 at least some reasons for thinking it may prove to be typical rather than 

 exceptional in the topographic history of glaciated mountains. 



Another example of topographic conditions similar to those just cited 

 is furnished by the canyon of Rush creek, near Mono lake, California. 

 In the case of Rush Creek canyon, as is well shown on an admirable map 

 of the basin of Mono lake made by Willard D. Johnson,* a deep horse- 

 shoe-shaped valley is present at the eastern base of the Sierra Nevada, 

 which has four or five hanging valleys arranged along its precipitous 

 outer margin. Two of the tributary valleys were formerly occupied by 

 valley glaciers, and where they enter the main valley, at right angles to 

 its course, there is a steep descent of about 1,600 feet, and two others of 

 the tributary hanging valleys are little more than cirques, and enter the 

 main valley at about the same horizon as the larger tributaries and also 

 at about the level of the highest lateral moraines in the lower valley. 

 The main valley had essentially no source of snow supply except the 

 contributions from its own hanging valleys, and it is inconsistent with 

 the known behavior of glaciers to assume that the tributary glaciers 

 from the lateral valleys abruptly changed their direction of flow and at 

 the same time and at localities in definite alignment one with another 

 deepened their troughs at least 1,600 feet in excess of their upstream 

 portions. On the contrary, the facts just referred to are in harmony 

 with the view that the horseshoe-shaped portion of Rush Creek canyon, 

 and at least the larger of its tributary valleys, were in existence previous 

 to the development of the glaciers of that region and gave direction to 

 the glaciers which occupied them. In this instance, as in the case of 

 Kieger canyon, pre-Glacial topographic conditions seem clearly to have 

 given direction to the flow of the ice which occupied the canyon and to 

 have been modified by ice abrasion to only a secondary degree. 



Returning to the consideration of Stein mountain, it is situated about 

 180 miles east of the Cascade range, is of about the same height as that 

 range, is composed of similar rocks, and, so far as can now be judged, 

 was upraised at about the same time that volcanic eruptions built the 

 principal part of the larger mountains. It may therefore reasonably be 

 assumed to have experienced the same climatic changes as the Cascade 

 range, but in a less intense degree. Its history may, as it seems, be 

 taken as a simplified example of the more voluminous and more com- 

 plex records of events inscribed on the greater mountain with which it 

 is somewhat remotely associated. I venture to assert, in part from per- 



* Israel C. Russell : "Quaternary history of Mono valley, California." Eighth Annual Report, 

 part i, U. S. Geol. Survey, plate xvii. A description of Rush Creek canyon, etcetera, is contained 

 in the same report. 



