It is an interesting fact that in the Cordilleran region the mountains have been increasing in height in very recent years. We might almost say that they are growing to-day. In this region, then, we can actually see how mountains are made; we do not have to depend upon descriptions of the manner in which they are supposed to have been made thousands of years ago.
FIG. 22.—BLUFF FORMED BY AN EARTHQUAKE
At the foot of the Wasatch Range, Utah
Any good map will show that the mountains of the Cordilleran region have in general a north and south direction. Their direction was determined by fissures formed long ago in the crust of the earth. Movements have continued to take place along many of these fissures up to the present time, and probably will continue for some time to come.
In order to become better acquainted with these remarkable mountains, let us examine some of them, taking first the Wasatch Range in eastern Utah. The range has an elevation of nearly eleven thousand feet, rising gradually upon the eastern side, but presenting a bold and picturesque front upon the west, toward the plain of Great Salt Lake. A short drive from Salt Lake City brings us to the foot of the range, at the mouth of Little Cottonwood Cañon.
A peculiar bluff which extends for a number of miles along the base of the mountains at once attracts our attention. The steep face of the bluff, which is from fifty to seventy-five feet high, appears to have been formed by a rising of the land upon the side next the mountains, or a dropping upon the valley side. There are reasons for believing that the formation of the bluff was due to the occurrence of an earthquake some time within the last century. The bluff is closely related to the mighty mountains behind it. It was formed by the last of a series of movements in the earth which raised the great block known as the Wasatch Range to an elevation of six thousand feet above the plains at its base. Is it to be wondered at that disturbances of the earth which result in the erection of mountains of such height are frequently so severe as to destroy the strongest buildings?
Now let us go westward across the various parallel ranges of the Great Basin to Owens Valley at the eastern base of the Sierra Nevada mountains. This is the highest and longest continuous mountain range in the United States. For a distance of more than one hundred miles its elevation is from twelve thousand to over fourteen thousand feet.
FIG. 23.—EASTERN FACE OF THE SIERRA NEVADA MOUNTAINS