been rapidly cut into such great upheaved blocks form part of the
world's most striking scenery. The Grand Canyon of the Colorado
with its tremendous platforms, mesas, and awe-inspiring cliffs
could have been formed in no other way. Equally wonderful are
some of the narrow canyons in the broadly upheaved plateaus of
southern Utah where the tributaries of the Virgin and other
rivers have cut red or white chasms thousands of feet deep and so
narrow that at their bottoms perpetual twilight reigns. It is a
curious proof of the fallibility of human judgment that these
great gorges are often cited as the most striking examples of the
power of erosion. Wonderful as these gorges certainly are, the
Piedmont plain or the northwestern peneplain is far more
wonderful. Those regions had their grand canyons once upon a
time, but now erosion has gone so far that it has reduced the
whole area to the level of the bottoms of the gorges. Though such
a fate is in store for all the marvelous scenery of the western
cordillera, we have it, for the present at least, as one of the
most stimulating panoramas of our American environment. No man
worthy of the name can sit on the brink of a great canyon or gaze
up from the dark depths of a gorge without a sense of awe and
wonder. There, as in few other places, Nature shows with
unmistakable grandeur the marvelous power and certainty with
which her laws work out the destiny of the universe.

In other parts of the great American cordillera some of the
simplest and youngest mountain ridges in the world are found. In
southern Oregon, for example, lava blocks have been broken and
uplifted and now stand with steep fresh faces on one side and
with the old surface inclining more gently on the other. Tilted
blocks on a larger scale and much more deeply carved by erosion