20 GEOLOGICAL AREAS OF CANADA, 



schists. It is through these ranges, therefore, rather than along the 

 line of the " Rocky Mountains " as defined on maps, that the core of 

 the great chain would seem to be continued to the north. 



(2.) The District of the Central Table-Land. — This district com- 

 prises the great plateau which extends from the Selkirk and other 

 mountain ranges, on the east, to the Cascade and Coast Mountains 

 on the west. It lies at an average elevation of from 2,000 to 4,000 

 feet above the sea, and presents for the greater part a more or less 

 mountainous character. Numerous lakes occur upon its surface 

 and it is traversed by the Columbia, Fraser, and other rivers, floAving 

 mostly in deeply-cut channels or canons. In many places it is thickly 

 wooded ; but gravelly and comparatively sterile tracts prevail over 

 considerable areas, and swamps are also numerous. So far as known 

 at present, its lower rocks appear to consist of granitic, talcose, and 

 micaceous formations (more or less tilted or contorted), succeeded by 

 shales, conglomerates, and limestones of Middle and Upper Palseozoic 

 age, or by more recent strata of altema,ting sandstones, shales and 

 lignites, with bedded volcanic products (partly of trappean, and partly 

 of scoriaceous lava-like aspect) — the whole overlaid, very generally, 

 by accumulations of sand and gravel. The latter, as seen more 

 especially in the valleys of the Fraser, Thompson, and other rivers, 

 often form sharply-defined terraces or beaches at vai'ying elevations 

 on the flanks of the older rocks. These sands and gravels, especially 

 in the streams which descend from the Cariboo and Gold ranges, and 

 in the valley of the Lower Fraser, are more or less auriferous. The 

 lignite-bearing strata an(i associated volcanic beds are probably in 

 part Cretaceous, although chiefly of Cainozoic age. 



(3.) The Coast and Western Mountain District. — This is essentially 

 an alpine region, forming the western margin of the high Table-land, 

 and extending from the latter to the coast-line of the Pacific Ocean. 

 With the exception of some comparatively restricted areas u.pon the 

 coast, as at the mouth of the Fraser and smaller rivers, it is occupied ■ 

 entirely by the northern ranges, and their spurs, of the Cascade 

 Mountains, which present an average elevation, in this district, of 

 from 5,000 to 7,000 feet above the sea, with perhaps here and there 

 a peak of somewhat higher altitude.* Glaciers occur in many of the 

 higher gorges ; and deep fiords, between, in many places, high walls 



* Mt. Baker, Mt. Hood, and Mt. Eegnier or Rainier, although referred to in many works on 

 Physical Geography as belonging to British Columbia, lie south of the Province boundary-line 

 as now adopted— i.e., the parallel of 49°. 



