This ends the brief geologic story of Colorado National Monument, except
for a peek into the future, a description of trips through and around
the Monument, and a comparison with other Parks and Monuments on the
Plateau. The temporary nature of lakes, rivers, and even mountains has
been discussed—the Monument of today and the new course of the Colorado
River are no exceptions.
The Colorado River did not solve its problems by abandoning its
hard-rock course in Unaweep Canyon in favor of a soft-rock course
through Ruby and Westwater Canyons—it just postponed them. The river has
again cut down into its old nemesis—the hard Proterozoic rock—in Ruby
Canyon just within the Colorado border, in Westwater Canyon in Utah, and
the Gunnison River has reached the hard rock at its confluence with
Dominguez Creek, not far above Whitewater, as shown in figure 34_D_.
Thus, once again hard rock is slowing down old man river, and will slow
him down for a long time to come. Someday, Westwater and Ruby Canyons
will be deep gorges like Unaweep Canyon. Then it is quite possible that
another young tributary may sneak around the Uncompahgre arch some miles
northwest of these canyons and pirate the river into a new soft-rock
course.
By this time, the Monument will have changed appearance considerably.
Some of the canyons will have come together by eating away the ramparts
that separated them—just as the two entrances of Monument Canyon have
already done. But as the lower canyons thus eliminate themselves, the
headwaters will bite deeper into Piñon Mesa, so perhaps the Monument
will simply creep slowly southwestward. However, renewed uplift, more
volcanos, changes in climate, or other events could alter the picture.
Still, if the geologic clock ran as fast as the ones we use, the picture
of the Monument we see today would be on the screen only a small
fraction of a split second. But the geologic clock ticks on, slowly but
surely, and, someday, the Holocene Epoch in which we live will become
just another brief chapter in the long geologic history of the Earth.
[Illustration: Petroglyph]