HIGH PENEPLAIN 123 



ference rests partly on the trends of structure lines deter- 

 mined by the Canadian Geological Survey in neighboring 

 parts of the continent, partly on the trends of the straighter 

 valleys and channels of the region itself. 



From this complex the pre-Pleistocene topography was 

 developed by erosion. The only constructional forms we 

 saw which might have antedated the Ice Age were a few 

 volcanic cones. The system of relief was related to three 

 known base-levels. The plane of the first is now high in 

 air, above some of the mountains and among the peaks of 

 others. The second is not far from present sea-level, and 

 the third is below sea-level. 



The High Peneplain. The uplands of the mainland 

 are remarkably uniform in general height over large areas, 

 not indeed presenting plain surfaces, but either exhibiting 

 harmony of crest lines, despite profound and general dis- 

 section, or else occupied by numerous small shallow val- 

 leys, which are strongly contrasted with the deep steep- 

 walled trenches of a less complete dissection. These 

 features can be most readily presented in connection with 

 some of the accompanying illustrations. Figures 3, 61, 

 62, 63, 75, and 77 were drawn from photographs by the 

 Canadian Boundary Commission. 



Figure 61 shows the upland topography north of the 

 western end of Cross Sound. (The reader can identify 

 the locality on the map, page 120, as the third cape west 

 of the mouth of Glacier Bay.) We stand on a summit 

 above Cape Spencer, and look northwest. At the left is 

 the Pacific Ocean; in the center distance, the end of 

 Fairweather Range (the nearest high peak being La Pe- 

 rouse, 10,750 feet) ; at the right, Brady Glacier, its foot 

 separated from Taylor Bay by a gravel strand. Between 

 us and the base of the mountains, 18 miles away, are a 

 series of hills somewhat uniform in height. The higher 

 points (as we learn from the Commission's contour map) 



