INTERIOR AND YUKON PLATEAUS 123 



which lies between the Coast range and the Rocky mountains has an 

 average width of about 100 miles and a mean elevation of 3,500 feet. 

 The plateau character of its surface is recognized only when it is viewed 

 in a broad way and contrasted with the mountains by which it is bor- 

 dered. It is cut off from the great lava plain of the Columbia river, on 

 the south, by some moderatel}^ high interpolated mountains near the 

 49th parallel, and on the north it is interrupted near latitude 55° 30' by 

 the ends of several ranges lying between the greater mountain features 

 on either side. Beyond the northern end of the Interior plateau, the 

 interval between the Rocky mountains and the Coast range appears to 

 be occupied by an irregular mountainous country extending toward the 

 northwest for a distance of 250 miles, where, in the vicinity of the 58th 

 parallel, a plateau is again noted. The elevation near the mountains is 

 about 2,500 feet, but there is a gradual slope toward the northwest in 

 the upper drainage basin of the Yukon river.* The general character 

 of the Yukon plateau is similar to that which the corresponding feature 

 exhibits in British Columbia. The interstream areas rise to a height of 

 from 1,500 to 2,000 feet or more above the beds of the rivers, and it is 

 only when a broad expanse of country comes under the eye that the 

 plateau character is recognized. The average width of the Yukon plateau 

 from the northern front of the Saint Elias range to the bounding moun- 

 tains on the Yukon river is about 180 miles. The feature extends west- 

 ward, touching Bering sea at various places, and probably merging with 

 the tundra which quite generally borders the open ocean on the west. 



The Interior and Yukon plateaus are generally admitted to be uplifted 

 peneplains. 



Correlation of Peneplains 



Two lines of evidence lead to the conclusion that the peneplains which 

 have been described in the preceding paragraphs are mutually equiv- 

 alent. The history of the drainage features throughout the province, 

 which furnishes at once the most acceptable and territorially the most 

 widely applicable basis for this correlation, will be given in the next 

 section after directly comparing the attitudes and relations of peneplains 

 in adjacent physiographic belts. 



It is known that in the central and northern portions of the Coast 

 range the plateau-like crest of the mountains has a slope toward the 

 interior of the continent. This relation is to be observed in the vicinity 

 of the Stikine and Taku rivers and in the region adjacent to the White 



* George M. Dawson: The later physiographical geology of the Rocky Mountain region in 

 Canada, etcetera. Trans. Roy. Soc. Canada, vol. viii, 1890, sec. iv, p. 5. 



