Arthur Philemon Coleman

“ The broad valleys seem peaceful enough, and it is hard to imagine the relentless war of the river and its tributary torrents upon the mountains until one works out the cross-section which they have cut from the summits on one side to those on the other, and figures the many cubic miles of rock which have been destroyed and carried down to the plains by the flow of water. ”

“ As one climbs out of the main valleys, especially on the western side of the Rockies, when timber-line is passed, snow begins to show itself, and at length there are snow-fields draining into glaciers, which creep thousands of feet down into the valleys. Finally the warmth of the lower elevation balances their slow advance and from an ice cave at the end there flows a milky mountain torrent, loaded with the stones and gravel and rock flour ground from the rock floor of the glacier above. ”

“ From the higher levels one sees, too, how the glaciers eat back their U-shaped valleys into the solid rocks of the central mountain blocks, even little "cliff glaciers" carving for themselves nests shaped like a half kettle, cirques, as they are called in the Alps. ”

“ Passing through the Rockies by the lower valleys as in the Kicking Horse Pass, one sees mainly the work of running water. Where the river has a somewhat gentle slope, like the Bow, the valley which it has cut is broad and open, with terraces on each side sweeping with a curve up to the foot of the cliffs, which have their bases buried under vast heaps of talus blocks from above, mainly quarried by frost. ”

“ Above the snow-line the sculptors which shaped them are chiefly frost, the avalanche and the glacier; on the lower slopes frost and rain and torrents have done most of the work; while the larger rivers have sawn their way down through the rocks, hollowing canyons and broad valleys, and sweeping downwards toward the plains or the sea all the debris, the rocks and pebbles, the sand and the clay, delivered to them by the agents working at higher levels. ”

“ The raising of mountains is a difficult bit of engineering to explain, and geologists are by no means agreed as to the causes that thrust one part of the earth's crust skyward and sink other parts into ocean depths. The most commonly accepted cause is the shrinkage of the earth's interior, by cooling, or by the loss of gases, or by condensation due to gravity. In this process the solid outer crust becomes too large for the interior and must be crushed and crumpled to adjust itself. ”

“ In these upper regions the jointage of the rocks plays a large part, those with numerous joints, into which the water from thawing snow may sink by day, only to freeze at night and pry asunder the blocks, are quickly shattered even if of hard materials; while rocks with few open fissures stand their ground far better and rise amidst the slopes of debris as walls or pinnacles. ”

“ Hard quartzite or solid limestone resist best and stand out as cliffs and ridges, while softer slates and sandstones crumble and slide, giving long slopes of loose scree into which the foot sinks, the whole surface often slipping with the climber. ”

“ During all this time of slow growth in height the destructive forces were at work, frost and weather and running water and ice, tearing down the structures just as they do now, though the constructive forces were more than a match for them, at least in the earlier history of the mountains. The present forms of the Rockies are due then to a balance between the upbuilding and the down-tearing influences which have been at work during the past millions of years since the end of Cretaceous times. ”

“ Hundreds or even thousands of summits rise from ten to twelve thousand feet above the sea, but very few get above that limit. Some geologists account for this by supposing that a vast tableland has been elevated and then carved into the innumerable crests and valleys; but it is very doubtful if such a tableland ever existed. Certainly no important remnant of it can be recognized now. It seems more probable that the higher summits, rising with steep slopes much above the protecting snowfields, have been more rapidly attacked by frost and storms, and so have paid the penalty of greatness. ”

“ The higher the summit the more rapidly it is cut down, till it reaches a level where slopes are gentler and snow and ice give some protection from erosion; and so there is a tendency to uniformity of height. ”

“ The fundamental structure of the Rockies is simple when contrasted with the complex foldings and faultings in different directions shown by the Alps. The folds in our mountains are often rather broad and uncomplicated, especially toward the Pacific side of the range; while toward the northeast vast blocks of the sediments. ”

“ We must not think of this process as taking place suddenly in one mighty convulsion, but very deliberately, a small push with its earthquake shock, followed by a long quiescence before the next instalment of elevation; so that age by age the mountains grew, perhaps are growing even yet. ”

“ The loftiest mountains must always be geologically young, for, once elevated, every century means wear and tear and loss, till finally only stumps remain, as in the most ancient ranges of America, the Laurentide Mountains of northeastern Canada. ”

“ Towards the middle of the Rockies the tilted blocks of the eastern side give place to broad folds, more or less dome shaped at times, where there are wide anticlines; while at others the anticlines have been destroyed and shallow synclinal forms make the mountain tops. ”