CANADIAN AND MONTANA ROCKIES 



303 



history will be considered in a later chapter. Quoting from Lord et al. 

 (1947): 



The western system includes the St. Elias, Coast, Cascade, and Vancouver 

 Island Mountains. The St. Elias Mountains occupy an area in the extreme north- 

 west corner of British Columbia and adjacent southwestern Yukon. They are 

 the highest in Canada, extremely rugged, and in large part covered by an ice- 

 field. The elevation of Mount Logan, the highest peak in Canada, is 19,850 feet, 

 and other peaks exceed 15,000 feet. 



The Coast Mountains occupy a belt 100 miles wide and 1,000 miles long, and 

 border the Pacific coast from Yukon southeast almost to the International Bound- 

 ary at the 49th parallel. They rise abrupdy from the sea, and towards the axis 

 of the range are characterized by an almost unbroken succession of bare, rugged 

 peaks and saw-toothed ridges rising to elevations from 7,000 to more than 

 13,000 feet. Alpine glaciers and icefields are common, and in a few places in 

 the northern half of the range valley glaciers extend to sea-level. The range is 

 crossed by a number of deep river valleys, and its western margin is pene- 

 trated by numerous, long, narrow fiords continued inland by deep U-shaped 

 valleys. 



The Cascade Mountains project into Canada from the State of Washington 

 and are more than 100 miles wide where they cross the border. They lie on the 

 east side of lower Fraser River Valley, which separates them from the Coast 

 Mountains, and extends as far north as Thompson River. Many of the higher 

 peaks and ridges near the International Boundary attain elevations between 

 7,000 and 8,500 feet; and they are fully as rugged as those of the adjacent 

 Coast Mountains, and, like them, hold many alpine glaciers. 



Mountains occupy most of Vancouver Island and culminate, in the central 

 part, in peaks 5,000 to 7,000 feet or more above sea-level. The western side of 

 the island, like the western side of the Coast Mountains, is characterized by an 

 intricate set of fiords and by heavily timbered rocky slopes that rise abrupdy 

 '• from the sea to heights of several thousand feet. A lowland as much as 10 miles 

 wide borders the east coast. 



Central System 



The central system, like the western, is for the most part fundamentally 

 Nevadan in its geology. Its present geomorphic characteristics are ade- 

 quately described by Lord et al. ( 1947 ) . Referring again to the map of 

 Fig. 20.1 and quoting from them: 



The central system, composed of dissected plateaux and scattered mountain 



ranges, occupies a belt that averages more than 200 miles wide and extends 



,i southeast from the Alaska Boundary at Yukon River to the southern boundary 



of British Columbia at Okanagan River. In Yukon it includes the Yukon Plateau 



and Ogilvie, Selwyn, Pelly, and other mountains. In British Columbia north of 



latitude 54 and 55 degrees it includes Cassiar and Omineca Mountains, Babine 

 and Bulkley Mountains, and Stikine Plateau. In the southern part of the prov- 

 ince, it comprises the Interior Plateau and Cariboo, Monashee, Selkirk, and 

 Purcell Mountains. 



Yukon Plateau in Canada includes much of the drainage basin of Yukon 

 River and, commencing in northern British Columbia near Adin and Tcslin 

 Lakes, extends northwestward through Yukon and thence westward into Alaska 

 It has been deeply dissected by a drainage system whose main channels are 

 several thousand feet deep, and the once gently rolling upland has been broken 

 into a series of high, flat-topped hills and ridges. Ogilvie and Selwyn Mountains 

 border it on the north and northeast respectively, and to the southeast the 

 plateau ends against Pelly Mountains. 



Little is known about Ogilvie and Selwyn Mountains. The former, with bor- 

 dering peaks as high as 7,000 feet, extend easterly from the Alaska boundary, 

 near latitude 65 degrees, for 150 miles. There they join Selwyn Mountains, 

 which form the northeast rim of the Yukon Plateau and stretch nearly 400 miles 

 southeasterly to end in low country east of Frances River near latitude 61 

 degrees. Selwyn Mountains rise from the Plateau along an irregular front, and 

 are broken into groups of mountains by broad valleys and other depressions. 

 Probably a few peaks are more than 10,000 feet above sea-level, and many rise 

 to elevations in excess of 7,000 feet. Selwyn Mountains are bordered on the 

 northeast by the Mackenzie Mountains of the eastern physiographic subprov- 

 ince. 



Pelly Mountains form a triangular area in the southern part of the Yukon 

 Plateau, with corners near Teslin Lake, Frances Lake, and Pelly River at longi- 

 tude 135 degrees. They include Glenlyon, Pelly, and Big Salmon Ranges, and 

 rise from adjacent plateau areas through border areas characterized by long, 

 smooth-topped spurs and dissected tablelands. The highest peaks of the main 

 unit, the rugged Pelly Range, may be more than 8,000 feet above sea-level, and 

 hold a few small alpine glaciers. 



Cassiar and Omineca Mountains constitute a continuous belt stretching 450 

 miles northwesterly from near Takla Lake into Yukon, and extending 50 to 75 

 miles west from Finlay and Parsnip Rivers. These mountains comprise a great 

 number of ranges separated by broad, transverse and longitudinal vallej s se\ - 

 eral thousand feet deep. The higher peaks and ridges range in elevation from 

 6,000 feet to more than 8,000 feet. Permanent ice is confined to rather small. 

 scattered, alpine glaciers. 



Babine and Bulkley Mountains and their northerly extensions occupy an area 

 of more than 20,000 square miles, bounded on the east by Cassiar and Omineca 

 Mountains, on the south by the Interior Plateau, on the west bv the Coast 

 Mountains, and on the north bv Stikine Plateau. Bulklev and Babine Moun- 

 tains lie on either side of the northwesterly trending Bulkley-upper Skeena 

 Valley. They comprise many individual mountains or mountain groups isolated 

 by wide low areas or great valleys. Most peaks are highly dissected, and some 

 rise more than 7,500 feet above the valleys. 



Stikine Plateau occupies much of the drainage basin of Stikine River east of 



