In the St. Elias region the mountains have been produced by upheaval, and are not volcanic in their origin. The frequently repeated statement that Mount St. Elias is a volcano is incorrect. Although igneous rocks occur near its summit, they are of the nature of dikes or intrusions, probably of ancient date, and not lava-flows. The principal volcanic mountains of Alaska are farther west in the region of the Alaskan peninsula and the Aleutian Islands. This western extension of the continent is excessively rugged, but the mountains rise directly from the ocean and in part form a chain of precipitous islands with irregular topographic forms.
There are mountain ranges also in the central and northern portions of Alaska and the adjacent part of Canada, but this region awaits exploration, and but little accurate information concerning its topography is on record.
The Mountains of Western Canada.—Reference has already been made to the differences in the nomenclature applied to the portions of the Pacific mountains on opposite sides of the United States-Canadian boundary, and at present this lack of harmony cannot be adjusted. As is well known, the great Pacific cordillera crosses the boundary nearly at right angles, and there is no abrupt change in the topography of the land. From the western border of the Great plateaus to the Pacific, between the forty-fifth and fifty-sixth parallels, as stated by the Geological Survey of Canada, the cordillera has an average breadth of about 400 miles, and is composed of four great mountain chains, named in their order from east to west, the Rocky, Gold, Coast, and Vancouver Mountains. These four great chains are nearly parallel and have irregular northwest and southeast trends.
The Canadian Rockies rise abruptly from Great plateaus in which the rocks are nearly horizontal, and have a complex structure, due to the folding and other disturbances that have affected the strata. Deep dissection by stream erosion has occurred, as is the case generally throughout the Pacific cordillera, and the peaks and ridges remaining are remarkable for their grandeur. Although less elevated than the higher portions of the same great belt in the United States, many of the summits are from 8,000 to 10,000, and, as reported, in a few instances reach 13,000 feet in height, while the passes range is elevated from about 4,000 to 7,000 feet. The western border of the Rocky Mountain range is well defined for a distance of some 700 miles to the northward of the international boundary by a remarkably straight, wide valley, which is occupied by the head waters of several large rivers, namely, the Kootenay, Columbia, Fraser, Parsnip, and Findley. To the west of the great valley just referred to rises the Gold system, composed principally of the Selkirk, Purcell, Columbia, and Caribou Ranges. It is in this rugged region that some of the most remarkable of the splendid scenery of western Canada occurs.
To the west of the Gold system is a broad region of valleys and lesser mountains, known as the interior plateau of British Columbia, which is a northward extension of the Great Basin region of the United States. The breadth of this belt of comparatively low country is about 100 miles. Like the similar region in Washington and Oregon, it is without forests, but favourable as a grazing country. In part it is occupied by extensive lava-flows, similar to the Columbia River lava of the northwestern part of the United States.
The Coast Mountains of Canada, although stated by geologists to be distinct from the Cascade Mountains, are in part at least, as determined by the present writer, a direct northward extension of that range. The average elevation of the higher peaks in the Canadian Coast Range, as it is termed, is between 6,000 and 7,000 feet, while the culminating points reach an elevation of about 9,000 feet. How
far northward the nomenclature applied to the Pacific mountains in southwestern Canada will be found applicable can not be stated, as the region to the north of the fifty-sixth parallel is almost wholly unknown.
THE ANTILLEAN MOUNTAINS
As has been clearly pointed out by R. T. Hill, the Pacific cordillera ends at the south in south-central Mexico, while the Andean cordillera at its northern end terminates in the rugged mountains of Venezuela to the south of the Caribbean Sea. These two great cordilleras do not overlap, but there is a difference of about 10 degrees of latitude between them, and if extended they would pass each other at a distance of nearly 1,000 miles. In the space thus indicated, measuring some 600,000 square miles, is included the southern portion of Mexico, Central America, and the West Indies. The rocks in these countries present a great series of folds which trend in an easterly and westerly direction, and thus present a conspicuous exception to the major structural features of both North and South America. To this newly recognised division of the larger geological and geographical characteristics of the New World the name Antillean mountains has been given.