The work of mountain building is still active in the western cordillera, as is evident from such an event as the San Francisco earthquake. In the Owens Valley region in southern California the gravelly beaches of old lakes are rent by fissures made within a few years by earthquakes. In other places fresh terraces on the sides of the valley mark the lines of recent earth movements, while newly formed lakes lie in troughs at their base. These Owens Valley movements of the crust are parts of the stupendous uplift which has raised the Sierra Nevada to heights of over 14,000 feet a few miles to the west. Along the fault line at the base of the mountains there runs for over 9.50 miles the world's longest aqueduct, which was built to relieve Los Angeles from the danger of drought. It is a strange irony of fate that so delicate and so vital an artery of civilization should be forced to lie where a renewal of earthquake movements may break it at any time. Yet there was no other place to put it, for in spite of man's growing control of nature he was forced to follow the topography of the region in which he lived and labored. On the southern side of the Mohave Desert a little to the east of where the Los Angeles aqueduct crosses the mountains in its southward course, the record of an earthquake is preserved in unique fashion. The steep face of a terrace is covered with trees forty or fifty years old. Near the base the trees are bent in peculiar fashion. Their lower portions stand at right angles to the steeply sloping face of the terrace, but after a few feet the trunks bend upward and stand vertically. Clearly when these trees were young the terrace was not there. Then an earthquake came. One block of the earth's crust was dropped down while another was raised up. Along the dividing line a terrace was formed. The trees that happened to stand along the line were tilted and left in a slanting position on the sloping surface between the two parts of the earth's crust. They saw no reason to stop growing, but, turning their tips toward the sky, they bravely pushed upward. Thus they preserve in a striking way the record of this recent movement of the earth's crust.