From Norton's "Elements of Geology." By permission of Ginn and Company
A BABY MOUNTAIN THAT STOPPED TO REST
A mountain, as you can readily imagine, isn't made in a day. Here is a little mountain near Hancock, Virginia, that started up ages ago and then stopped to rest; one of the ripples in which the great Appalachian waves died away. This baby mountain has no granite mass in its centre, as big mountains have, because the wrinkling didn't reach down far enough into the earth to release the pressure on the molten rock.
Why should mountains show such a fancy for salt water? It seems strange, doesn't it? I know why it is because I helped make a mountain myself once—up on the Canada Coast it was—and I learned a good deal of the mountains and their ways. I will tell you about the mountains and the sea a little later; after I have told you some other things. First of all, this is how the Granite family helped make mountains. As the great stone sides of the mountain rise the enormous pressure on the melted rock farther down in the earth is released, and is forced up under the mountain as it rises. Then, cooling, it crystallizes into granite, as explained on [page 131].
MOUNTAINS MADE TO ORDER
Of course nobody ever watched a mountain crumpling up in the way mountains are believed to crumple up, the process is so slow. Yet, to try out the theory, geologists in the universities make layers of different material, corresponding to the strata of different kinds of stone, and then subject this composition to pressure at both ends, as the earth crust is supposed to be pressed in the crumpling process. The result is that these artificial strata take similar forms to those we see in mountain rock. And that's the answer!
Notice the similarity of the rock wrinkles in the baby mountain in Virginia and these imitation mountains of the laboratory.
WHY MOUNTAINS RUN NORTH AND SOUTH
Look at your relief map once more. Which way do the mountains run in North America? In South America? In Africa? They all run in a general north and south direction, don't they? Do you see why? The fact that they were made along the coasts of the oceans would make them run north and south, too, wouldn't it? The same thing explains why the Alps do not run north and south. They were made by the sinking of a sea that runs east and west, and so they started out to run east and west, too; then they got a wrench, the particulars of which we need not go into here, and were much mixed up, as we find them to-day.