There
Is Circumstantial Evidence, Amounting Almost To Proof, And Figure 3 Of
Plate Facing Page 99 Suggests What That Evidence Is.
It should be carefully
noted that the Canyon has been cut through the highest portions of a ridge,
which runs generally from east to west, and the slopes of which, therefore;
were north and south from the ridge.
As one travels north from the Canyon,
he finds all the way along, for hundreds of miles, that he goes on a down
slope for a number of miles and then suddenly comes to the jutting edges of
slightly tilted strata (only 2 degrees) which make a cliff up which he must
climb. Arrived at the top of this, the downward descent begins again, until
another ridge of these slightly tilted strata appears, see Figure 3 of
plate facing page 99. Thus he continues up into Utah, and south and east
into Arizona.
Now, in imagination, restore these cliffs of Permian, Triassic, Jurassic
and even Cretaceous strata over the whole Canyon platform. Figure 4 of
plate facing page 99.
Red Butte, which is the prominent landmark seen from the railway on the
right, when going from Williams to the Canyon, is said to be a remnant of
the Permian.
Deposition of Strata in Shallow Water. It is, I believe, generally accepted
by the geologists that the accumulation of much of the sediments of the
Cambrian, Carboniferous, Permian, Triassic, Jurassic and Cretaceous periods
took place in shallow water, and that the sea bottom slowly sank under the
weight of the increasing deposits. Hundreds, thousands of years must have
elapsed during the process, for the indications are that the sinking did
not exceed a few inches every hundred years! As carefully measured, these
sediments then amounted to about two miles. Imagine, then, these Cambrian
rocks, that at El Tovar are clearly seen above the "granite" or Archaean,
sunk in the ocean, to the depth of two miles, and covered over with the
various strata, the topmost of which was barely above sea level at periods
of low tide.
Cretaceous Uplift. Then began another epoch of uplift. Slowly the
Cretaceous rocks emerged from the sea, and were subject to the fierce
attacks of nature that produce erosion. Now we have to grope blindly for a
while, as the wise ones do not have facts enough upon which to speak with
definite certainty. But it is assumed that a great warping of the earth's
crust took place, and that in this revolution some of the plateau
sank, - supposedly the northern part, though it certainly extended across
the Canyon nearly as far south as Williams and Ash Fork, and other
parts - the edges - arose, and thus formed a basin which became another vast
inland sea.
Eocene Lake. We know this was an inland sea, and had no connection with
the ocean, for all the fossils and sediments deposited in it reveal that
they are fresh-water organisms. In this sea, as in the earlier oceans, vast
deposits of sediment were made in the early Eocene period, and another
period of subsidence occurred. Then the great lake was drained, and the
uplift began, slow and sure; then, and not before, were the conditions
existent that have made the Canyon country as we see it to-day. Peaks and
islets received the rainfall, tiny rivers were formed that grew larger and
cut their way in deeper, as the uplift continued. The principal stream,
which was then born, was the Colorado. It is supposed, from various
evidences, that the rainfall was very much more abundant then than now, and
consequently the rivers had greater flow, and more eroding and carrying
capacity. The uplift continued, and the geologists tell us it did not cease
until about fifteen thousand feet, deposited since Cretaceous times, were
thrust up into the air. As almost all this mass of deposition has
disappeared from the immediate Canyon region, we are compelled to believe
that it has been swept away down the Colorado River to join the sands of
the Carboniferous and later periods in the Colorado Desert, the Salton
Basin, the great low region of Lower California, and the Gulf itself.
Less by Erosion in the Canyon Region. Now figure out for a few moments the
results of these different erosive periods. Eleven thousand five hundred
feet of Algonkian gone; a small amount of erosion in the Cambrian epoch,
the depth of which is unknown; and then the great denudation of the Eocene
period sweeping away upwards of fifteen thousand feet of strata, give us a
total of twenty-six thousand five hundred feet that have totally
disappeared from the Canyon region. A vertical mile is five thousand two
hundred and eighty feet. Mount Washington is about six thousand five
hundred feet above the sea, - a trifle higher than Mount Lowe, near
Pasadena, California. Take off from this six thousand five hundred feet,
say one thousand five hundred feet, for the level of the country at the
base of these two mountains, and then imagine a region five times as high
as both of them, covering an area of country of possibly thirteen thousand
to fifteen thousand square miles, slowly planed off by the erosive forces
of nature.
Formation of River Beds. How was it done? I have spoken of the peaks and
islets that first emerged from the Eocene Sea, and received the rains. Down
their slopes ran the earliest watercourses, first as rills, then as creeks,
finally as rivers. The higher the peaks ascended, the more the accompanying
land was lifted up, and therefore the longer and deeper became the rivers.
The course of a river once established, it is exceedingly difficult to
change it - hence the law that geologists call "the persistence of rivers."
By and by, the uplifted country appeared as one vast area of river valleys,
separated by stretches of plateau. Little by little, working by laws that
are pretty well understood, the swift flowing avers cut downwards. When
their velocity ceased, the widening of the river courses began, and
progressed with greater rapidity, so that, in time, the divides that
intervened between the rivers were worn away, - a process rudely shown in
Fig.
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