Fig. 14.—Sketch map showing the trace of the great fault fracture along which a renewed sudden movement of as much as twenty feet took place to cause the San Francisco earthquake of 1906. (After U. S. Geological Survey.)
The San Francisco earthquake of 1906 was produced by renewed movement along the great fault which extends lengthwise through the Coast Range Mountains for several hundred miles. It is literally correct to say that, for 250 miles along this great earth fracture, one part of the Coast Range instantaneously slipped from two to twenty-two feet past the other. More or less of the movement extended at least several thousand feet down into the earth. In this case both sides slipped and the movement was very largely horizontal rather than vertical. The land on the east side of the fault moved south and that on the west side moved north, the amount diminishing away from the fault on each side so that some miles out the actual crustal movement was only a few inches. When one thinks of the tremendous volumes of earth material involved in this shifting of the earth’s crust, is it any wonder that such destructive earthquake waves were produced? Many buildings were wrecked, several hundred people were killed, the disastrous San Francisco fire resulted, water mains were broken, and fences and roads crossed by the fault were dislocated as much as fifteen to twenty feet.
Plate 5.—Swift Current Valley in Glacier National Park, Montana. This was once a deep V-shaped canyon carved out (eroded) by stream action. Then a great valley glacier slowly plowed its way through it during the Ice Age and, by ice erosion, the present nearly straight U-shaped canyon has resulted. (Photo by Campbell, U. S. Geological Survey.)
Plate 6.—View in the Yosemite Valley from Near the Western Entrance. The great rock called “El Capitan,” on the left rises 3,500 feet above the river, and Bridal Veil Falls on the right is 620 feet high. All the rock is granite, the nearly vertical walls of which have resulted from the action of a great glacier which plowed its way through the valley during the Ice Age; the valley walls have been cut back by the removal of large vertical joint blocks. The flat bottom of the valley has resulted from the filling with sediment of a postglacial lake in the valley. (Photo by F. N. Kneeland, Northampton, Mass.)
During the great earthquake on the coast of Alaska in 1899 notable changes took place along the shore for some miles, one portion having suddenly risen as much as forty-seven feet, while another portion sank below sea level.