65 



Alaska into British Columbia. The character 

 of the scenery changes rapidly to the north of 

 the summit, becoming less rugged as the Yukon 

 Plateau is approached. Leaving the summit 

 the train runs along various small lakes and 

 streams to Lake Bennett. 



39.7 m. Bennett — Altitude 2,158 ft. (656 m.). At 



63.5 km. Bennett near the head of Lake Bennett, a stop 

 is usually made for luncheon. Continuing, the 

 train runs along the shores of the lake for 27 

 miles (43 km.), the scenery being particularly 

 beautiful. About 31 miles (50 km.) from the 

 summit, the 60th parallel of latitude is crossed, 

 which is the boundary between the provinces of 

 British Columbia and Yukon Territory. The 

 typical Coast Range intrusives continue along 

 the railway to a point about 11 miles (17 km.) 

 from Caribou, thence for 6 miles (9.6 km.) 

 porphyrites, andesites, basalts, tuffs, and tufa- 

 ceous sandstones and shales of Jura-Cretaceous 

 age outcrop along the railway. Thence for 

 about a mile, quartzites, slates, and limestones, 

 thought to be of Devonian age, are developed. 

 Typical granodiorites continue to Caribou. 



Lake Bennett and other similar bodies of 

 water forming the headwaters of Yukon river, 

 are of particular interest, and various theories 

 have been advanced to account for their origin. 

 It appears, however, that these lakes represent 

 the positions occupied by the last great tongues 

 of the retreating valley glaciers, and that the 

 ice melted so rapidly toward the last that the 

 depressions it occupied had not time to become 

 filled with glacial debris as did other valleys and 

 other portions of these valleys. 



The valley of Lake Bennett, which is really a 

 southern continuation of the broad depression 

 extending northward from Caribou toward 

 Whitehorse, is typically U-shaped, has high 

 precipitous walls rising abruptly from the 

 water's edge in places, and, particularly along 

 the western side of the lake, has had all pro- 

 jecting points and spurs planed away by north- 

 ward moving valley glaciers. Virtually all the 

 34883—5 



