Читать книгу The Book of the National Parks - Robert Sterling Yard - Страница 17

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The granite national parks are Yosemite, Sequoia, including the proposed Roosevelt Park, General Grant, Rocky Mountain, and Mount McKinley. Granite, as its name denotes, is granular in texture and appearance. It is crystalline, which means that it is imperfectly crystallized. It is composed of quartz, feldspar, and mica in varying proportions, and includes several common varieties which mineralogists distinguish scientifically by separate names.

Because of its great range and abundance, its presence at the core of mountain ranges where it is uncovered by erosion, its attractive coloring, its massiveness and its vigorous personality, it figures importantly in scenery of magnificence the world over. In color granite varies from light gray, when it shines like silver upon the high summits, to warm rose or dark gray, the reds depending upon the proportion of feldspar in its composition.

It produces scenic effects very different indeed from those resulting from volcanic and sedimentary rocks. While it bulks hugely in the higher mountains, running to enormous rounded masses below the level of the glaciers, and to jagged spires and pinnacled walls upon the loftiest peaks, it is found also in many regions of hill and plain. It is one of our commonest American rocks.

Much of the loftiest and noblest scenery of the world is wrought in granite. The Alps, the Andes, and the Himalayas, all of which are world-celebrated for their lofty grandeur, are prevailingly granite. They abound in towering peaks, bristling ridges, and terrifying precipices. Their glacial cirques are girt with fantastically toothed and pinnacled walls.

This is true of all granite ranges which are lofty enough to maintain glaciers. These are, in fact, the very characteristics of Alpine, Andean, Himalayan, Sierran, Alaskan, and Rocky Mountain summit landscape. It is why granite mountains are the favorites of those daring climbers whose ambition is to equal established records and make new ones; and this in turn is why some mountain neighborhoods become so much more celebrated than others which are quite as fine, or finer—because, I mean, of the publicity given to this kind of mountain climbing, and of the unwarranted assumption that the mountains associated with these exploits necessarily excel others in sublimity. As a matter of fact, the accident of fashion has even more to do with the fame of mountains than of men.

But by no means all granite mountains are lofty. The White Mountains, for example, which parallel our northeastern coast, and are far older than the Rockies and the Sierra, are a low granite range, with few of the characteristics of those mountains which lift their heads among the perpetual snows. On the contrary, they tend to rounded forested summits and knobby peaks. This results in part from a longer subjection of the rock surface to the eroding influence of successive frosts and rains than is the case with high ranges which are perpetually locked in frost. Besides, the ice sheets which planed off the northern part of the United States lopped away their highest parts.

There are also millions of square miles of eroded granite which are not mountains at all. These tend to rolling surfaces.

The scenic forms assumed by granite will be better appreciated when one understands how it enters landscape. The principal one of many igneous rocks, it is liquefied under intense heat and afterward cooled under pressure. Much of the earth's crust was once underlaid by granites in a more or less fluid state. When terrific internal pressures caused the earth's crust to fold and make mountains, this liquefied granite invaded the folds and pushed close up under the highest elevations. There it cooled. Thousands of centuries later, when erosion had worn away these mountain crests, there lay revealed the solid granite core which frost and glacier have since transformed into the bristling ramparts of to-day's landscape.