COPPER RIVER DISTRICT 121 



"The Chugach mountains occupy a coastal belt connected with the mountains 

 of the Saint Elias range toward the east and with Kenai peninsula toward the 

 west. The width of this belt is about 60 miles, and the mountain summits reach 

 an elevation varying between 5,000 and 7,000 feet, though usually grouped about 

 the elevation of 6,000 feet, while above this occasional peaks rise to perhaps 8,000 

 feet. To one who crosses the range by way of the valleys and low passes, this gen- 

 eral uniformity of level is not apparent ; but from any considerable elevation 

 within the region the impression is strikingly presented that the summits of the 

 Chugach mountains represent the surface of an ancient plateau from which the 

 mountain masses have been carved. 



" The plateau character is well seen from the foothills of mount Blackburn (in 

 the Wrangell group). The level crest line is a very striking feature to the eye, for 

 at a distance of 25 or 30 miles the details of the dissection which the plateau has 

 suffered since its uplift are lost, and only the upland is noted. On a clear day the 

 snow-covered peaks in the vicinity of mount Saint Elias may be plainly distin- 

 guished, rising high above the general level of the plateau." 



The tributaries of the Copper river, ramifying over an area of approxi- 

 mately 25,000 square miles, take practically all of the drainage of the 

 Chugach and Wrangell mountains. This extensive drainage system is 

 believed to have been developed during the erosion of the Chugach pene- 

 plain, and to have persisted with all, of its major characteristics, by 

 means of the active downcutting of stream channels continued pace by 

 pace with regional uplift. 



Peneplains in the Pacific Mountains 



The existing descriptions of the coastal mountains southeastward from 

 the Copper River region are few, but all of them are favorable to the 

 suggestion that the summits of the various ranges are representative of 

 uplifted peneplains. 



The only description we have of the southern portion of the Saint 

 Elias range is that of J. B. Tyrrell, but the partial quotation given is 

 sufficient to show the similarity of the physiography of this region with 

 that of the Chugach mountains. 



'* From Farrow mountain southwest of Aishihik lake the Chilcat range presents 

 the appearance of a vast white plain with the higher peaks rising above. It is a 

 vast plateau lying close to the Pacific coast. Farther north the mountains are 

 more rounded and graded. As a rule they rise 3,000 to 4,000 feet above the bot- 

 toms of the intervening valleys. 



"Standing on one of the summits, a great number of similar mountains may be 

 seen on every side, all about the same height and probably cut out of the same 

 extensive pre-Tertiary peneplain." * 



* J. B. Tyrrell : Bull. Geol. Soe. Am., vol. 10, 1890, p. 194. 



