Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/578

 528

CAN ADA

to over 4000 feet along the base of the Rocky Mountains. This interior plain of the continent represents the area of an ancient sea by which it was occupied in Mesozoic times. The Cretaceous and early Tertiary rocks by which it is in the main floored still lie nearly unaltered and undisturbed where they were deposited, although now raised far above the sea-level, particularly along that border impinging upon the Rocky Mountains where they are broken into foothills along the base of the range. These strata have been subjected to great denudation, but owing to their comparatively soft character this has been, in the main, nearly uniform, and has produced no very bold features of relief. Coals and lignite coals are the principal minerals of economic value met with in the area of this central plain, but its chief value lies in its vast tracts of fertile soil or of well-grassed uplands affording perennial pasturage for cattle, horses, and sheep. The Cordilleran Belt.—The wide mountainous Pacific border of the continent, constituting the “ Rocky Mountain region,” may best be named as a whole the Cordillera or Cordilleran belt. The Rocky Mountains proper in Canada comprise only the well-defined eastern system of ranges of this belt. The Cordillera includes nearly the entire province of British Columbia, with the whole of the Yukon district of the North-West Territories. Its width is about 400 miles, and it is throughout essentially a mountainous country, very complicated in its orographic features and interlocking river systems, but as yet in the main very imperfectly delineated on any maps. Two principal mountain axes may, however, be defined as its ruling features—the Rocky Mountains proper, above referred to, and the coast ranges of British Columbia. These run nearly parallel, and in a direction corresponding to that of the Pacific coast. Between them are many other ranges, but less regular in trend and much shorter, such as the Selkirk Mountains, the Gold ranges, and the Cariboo Mountains. There is also, in the southern inland country of British Columbia, a region which has, because of its essential difference from the adjacent mountain ranges, and although itself rugged and broken in character, been described as the interior plateau. This, beginning near the 49th parallel of latitude or international boundary, runs north-westwards for about 500 miles, with a general width of about 100 miles. It affords the greatest areas of arable land and pasture land comprised in British Columbia. Similar wide tracts of less broken country occur to the southward, between the mountain ranges in the Western States, and beyond it, to the north-west, after traversing an entirely mountainous region in the northern part of British Columbia, its physical characters are again to some extent repeated in the country on the Yukon watershed, where wide valleys and rolling hills alternate with short mountain ranges of no great altitude. The Pacific border of the coast ranges of British Columbia is dissected by a system of fiords perhaps unequalled elsewhere in the world. These represent submerged valleys, worn out by rivers on the steep western slope of the continent, when the land stood at a high level. A bordering mountain system of the continent, now also in a partly submerged condition, forms Vancouver Island and the Queen Charlotte Islands. The highest known mountains in the Cordillera of Canada are Mount Logan (19,500 feet), and Mount St Elias (18,000 feet), both situated near the intersection of the 141st meridian with the Pacific coast and on the borders of Alaska. The Rocky Mountains proper stand next in regard to altitude, frequently attaining 12,000 feet in their southern part, and with Robson Peak, the highest yet accurately measured, reaching 13,700 feet. Several summits in the Selkirks are known to surpass 10,000 feet, and many points in the coast ranges reach 8000 or 9000 feet.

[geography

Closely connected with the grand orographic features of this western region are its climate and its character as regards vegetation. It may, as a whole, be described as forest-clad, but forests of extraordinary luxuriance are found in the humid coast region. The conditions favourable to forest growth are to some extent repeated on the western slopes of the Selkirks, Rocky Mountains, and other main systems, on which the rainfall is ample. On the eastward slopes • and in the intervening lower tracts the forests are less dense, and considerable areas of dry, open grass - land occur in the interior plateau and in many of the larger valleys. The geological structure of the Cordilleran belt is very complicated, inasmuch as the rocks of this region have been subjected to repeated flexure and disturbance, recurrent up to a late date in the geological time-scale, and therefore including all but the most recent deposits. Rocks of Archaean age occur, particularly in and near the Selkirk ranges, which, with their representatives farther to the northward, are much older than either the Rocky Mountains proper or the coast ranges. The Rocky Mountains proper are referable to folding and fracture caused by pressure of the earth’s crust from the Pacific side, which has taken place chiefly at a date subsequent to the Laramie or closing stage of the Cretaceous. These mountains are mainly composed of Palaeozoic rocks, ranging from early Cambrian to Carboniferous in age, and consisting in large part of limestones. The coast ranges and that of Vancouver Island, carrying with them in their elevation portions of the Cretaceous rocks, are referable, in their present form, to the same or a not much earlier date. They, comprise, however, in their central parts, and particularly in the case of the coast ranges, great masses of granite that have welled up as “ bathylites ” along the axis of elevation. The coast ranges of British Columbia may, in fact, be considered in the main as a granitic belt, over 900 miles in length, and with a width of over 100 miles in many places. The interior plateau of British Columbia presents considerable areas of formations still nearly horizontal, and referable to various stages of the Tertiary or Cainozoic. These include the products of great volcanic activity, ending in the later Miocene in wide basaltic flows. Tertiary rocks are likewise found in some places fringing the Pacific coast, but with a limited spread. The Cordilleran belt, or Rocky Mountains region, as a whole, is the most important part of Canada in regard to mining. It constitutes the continuation to the north of the mining country of the western states of the American Union, and its length in Canada is equal to that in the United States. Its economic development has only begun in any systematic way, but great advances have already been made) means of communication have been provided in its southern part, and gold, silver, copper, lead, and other ores are now being worked on a large scale in that region. Coal has long been an important product of Vancouver Island, and valuable coalfields are now also beginning to be worked in the Rocky Mountains proper, in the valley of the Bow river, and along the line of the Crow’s Nest Pass. Attention was first directed to British Columbia as a mining countiy about 1858, when placer gold deposits began to be worked. The development of the rich Cariboo district followed with that of other districts less commonly known. Within the last few years the placer gold of the ukon basin, and more particularly that of the Klondyke division, has attracted world - wide attention, and all this northern mountain country, once valued only for its scanty harvest of rich furs, is being traversed and examined by the prospector. The alluvial gold deposits are naturally those first developed, but the lodes and veins from which these have been derived, together with the deposits of other