ountains 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.

Volcanoes as well as earth movements have occurred on a grand scale
within a few hundred years in the cordillera. Even where there is today
no visible volcanic activity, recent eruptions have left traces as
fresh as if they had occurred but yesterday. On the borders of the Grand
Canyon of the Colorado one can see not only fresh cones of volcanic
ash but lava which has poured over the edges of the cliffs and hardened
while in the act of flowing. From Orizaba and Popocatepetl in Mexico
through Mount San Francisco in Arizona, Lassen Peak and Mount Shasta
in California, Mount Rainier with its glaciers in the Cascade Range of
Washington, and Mount Wrangell in Alaska, the cordillera contains an
almost unbroken chain of great volcanoes. All are either active at
present or have been active within very recent times. In 1912 Mount
Katmai, near the northwestern end of the volcanic chain, erupted so
violently that it s