53 



The Coastal system from about the 50th to nearly 

 the 60th parallel of north latitude embraces only the 

 Coast range, if the islands to the west be considered to 

 form a separate range [29, p. 4; 30 pp. 61, 62], but this 

 simplicity is interrupted near the head of Lynn canal, 

 whence northward and northwestward, the Coastal system 

 consists of different ranges, in some cases separated by 

 wide valleys, as well as by other subordinate mountain 

 masses. The Coast range, after following the coast line 

 from Southern British Columbia to nearly the head of Lynn 

 canal, passes behind St. Elias range, and thence northward 

 constitutes the most easterly portion of the Coastal system, 

 becoming gradually less prominent until it merges into the 

 Yukon plateau near Lake Kluane, at latitude 61 ° and 

 longitude 138 30'. The Coast range consists, in a general 

 way, of an irregular series of peaks and ridges, that possess 

 but little symmetry other than a rough alignment parallel 

 to a northwesterly-trending axis. The range has every- 

 where a precipitous and jagged aspect, and consists largely 

 of knife-edged crests, rugged or even needle-like summits, 

 and sharply-incised valleys. The summits in the vicinity 

 of the White Pass and Yukon railway rise to altitudes of 

 5,000 to 6,000 feet (1,500 to 1,800 m.) above sea-level, 

 and on account of a certain uniformity of summit level, 

 which bears no relation to structural features, this terrane 

 has been considered by a number of geologists [33, p. 128; 

 66, p. 132; 6, pp. 286-290; 293] who have studied it topo- 

 graphically, to- represent a peneplanated or at least a 

 mature to old surface of erosion, subsequently elevated. 

 As mentioned in the Prince Rupert — Skagway section, 

 however, the evidence on this point does not appear to be 

 conclusive, and the uniformity of summit level may be 

 the result of various other causes. 



Bordering the Coastal system along its inland edge, 

 and stretching thence eastward, northeastward, and 

 northward to the Rocky Mountain system is the great 

 Interior system of plateaus and mountains, the most 

 northerly member of which, the Yukon plateau, has a width 

 in Northern British Columbia and Yukon of 250 to 300 

 miles (400 to 480 km.). In places some well defined 

 ranges or groups of mountains lie within this plateau 

 province. 



Into the upland surface of the Yukon plateau in 

 Southern Yukon, the main drainage courses have incised 

 channels varying from 3,000 to 4,000 feet (900 to 1,200 m.). 



