FIG. 1. Location of Fault line (after Gilbert). North of Pt. Arena the line passes under the ocean. The line has now been traced farther to the southeast than the map shows. a very short period, the waters on the north side of the fold flowed northward. Lands nearby were depressed and filled with water, forming marshes and sometimes permanent lakes. The latter still exist in Missouri, Arkansas and Tennessee. vices, muddy waters were thrown, geyser fashion, to a considerable height. To protect themselves from the danger of being engulfed in these crevices, the peopie felled trees at right angles to the crevices and built temporary homes on them. FIG. 2. Road near Olema (north of San Francisco). Not only is the road badly cracked, but the right side is a foot or two lower than the left side. These cracks represent the position of the stroyed property to the value of millions of dollars. In places large cracks were made in the ground, and at other places, depressions were formed. In point of violence, the shock was much smaller than those of the New Madrid earthquake referred to in the preceding paragraph. fault line. Within an hour, twelve minor shocks were noted, and others occurred later in the day, and on ensuing days. Prior to this event, earthquakes were not strangers in California. More than a century ago a shock was reported in the southern part of the state, and in 1868 one occurred FIG. 3. Road near Pt. Reyes Station (north of San Francisco). Before the earthquake the road was straight; now it is about 16 ft. out of line. The fault line cuts the road between the two straight stretches. gists have long known that the conditions along the Pacific coast of California are favorable to earthquake shocks. An earthquake is simply a shaking of the earth's crust and results from a jar. The latter may be produced by a volcanic explosion as in the cases of Krakatoa, Pelee, or Vesuvius. More commonly however, the jar is favorable for crustal movements which produce these jars and of course the resulting earthquakes. Especially is this true in young mountains, for the time that has elapsed since their formation may not have been sufficient to permit the readjustment of the rocks necessary that they may lie in an easier position. In consequence, the rock FIG. 4. Road near Inverress (north of San Francisco). Before the earthquake the road was about 8 ft. higher, its position being shown by the hat. The shocks produced many land-slides in this vicinity, and one of these carried the road down with it. youngest mountains in the United States, and moreover, are fractured along nearly vertical planes. Along these planes the rocks have been elevated on one side or depressed on the other, a condition known as a fault. Hence, not only may the rocks in these mountains lie in an uneasy pressed the opinion that the great earthquake had resulted from the movement of the rocks along one of these old faults. Subsequent investigation showed these forecasts to be correct. Area Affected and Intensity of Shock. The shock was felt as far north as Oregon and south as far FIG. 5. View near Stanford University. Before the earthquake the fence in the foreground was straight. Now the two panels make an angle. This has resulted from horizontal movement rectly over the fault line, but fortunately no town of importance was located on this line. Both east and west of this however, the shock was often severe. Further the severity was not always proportional to the distance from the fault line. Thus Santa Rosa lying about 20 miles east of the fault suffered greater of the land. for the great damage. To the west of the fault line the same general condition prevails, while those standing on more solid matter suffered less, even when nearer the fault line. The same principle applies in San Francisco also. Buildings constructed on loose earth, and espec |