Page:Canadian Alpine Journal I, 2.djvu/56

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The "EverlasingEverlasting [sic] Hills" have become proverbial, so that we are apt to think of mountains as the very emblems of stability and permanence, and very few except geologists ever inquire into their past to see how they were lifted up and sculptured to their present shape, or look into the future to forecast their ultimate fate. There is nothing more certain, however, than the fact that mountains, like every other creature of earth, have their birth, their youth, and middle age, and at last sink into decrepitude. 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.

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. This crushing and crumpling takes place along the lines of weakness, usually where sea and land meet, as in our Pacific coast region. There, from time to time, through the geologic ages the ocean floor has pushed itself inland, thrusting up the parallel ranges of British Columbia and Alberta, the Selkirks first and the Rocky Mountains last.