down and overridden by those of the mountains. These are only a
few of the countless forms of breaking, faulting, and crumpling
which have given to the cordillera an almost infinite variety of
scenery.

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