After many millions of tons had been thus ground up
and tossed about and mingled with the waters of the seas, the earth, in a
fit of fiery anger, turned and baked them, with intense heat, out of all
semblance to their former appearance. These baked masses, in the course of
time, were thrust up out of the seas, mashed and macerated once more, again
deposited as sand, silt, pebbles and boulders, and again burned. These
processes followed each other, how many times we do not know, the earth all
the while keeping up her steady uplift of the children of her bosom out of
the great sea. Higher and higher came the land. Further and further receded
the sea, until, in due course, the sun shone upon a vast area of land that
was the rude skeleton of what is now the continent of North America.
It would have taken a keen eye, however, to have imagined from that which
we see to-day what was there. The Gulf of California reached far up, even
into Nevada, and covered what are now the Mohave and Colorado Deserts;
there was no California Coast Range; the Gulf of Mexico was vastly larger
than it is to-day, covering all Florida, and reaching up the Mississippi
Valley half-way to the Great Lakes.
The First Strata. It was just preceding the last uplift of this epoch that
the era of deposition of rock debris was so prolonged that twelve thousand
feet of strata were washed into the bed of the sea, in the region now known
as the Grand Canyon Country. It was at the time when life was beginning to
dawn, for in the remnants of the strata are found fossils of the earliest
known life. These strata, therefore, are of immense interest to the
geologist, as they are the first known rocks containing life to emerge from
the primeval sea. Within the last few years, they have been called the
Algonkian Series, and later I shall speak of them more freely.
Prior to the deposition of these Algonkian strata, the Laurentian rocks
(the granite) upon which they rest were subject to a long period of
"planation," - as the grinding down and leveling of rock surfaces is termed.
After this planation was complete, a subsidence occurred; the whole area
became the bed of an inland sea, and upon the planed-down granite, the
debris that formed the Algonkian strata was washed.
While they were being deposited, the whole region was the scene of several
seismic and volcanic disturbances, for great dykes and "chimneys" of lava
are found, showing clearly that, by some means or other, the strata were
broken and shattered, cracked and seamed, and that through these cracks the
molten lava oozed - forced up from the interior of the earth. It spread out
over the Algonkian rocks in small sheets or blankets, which here and there
are still to be found to-day.
Tilting of the Algonkian Strata. Slowly this twelve thousand feet of strata
emerged into the sunlight. In the uplifting processes, the surface of the
earth, where they were, became tilted, and these strata therefore "dipped"
or "tilted" away from the perpendicular. As they emerged, weathering and
erosion began. It is most probable that this process of degradation began
and continued while the topmost strata were at or near sea level, so that
it was a simultaneous process with the uplift.
Erosion of the Algonkian. How many centuries this weathering and washing
away process consumed no one knows. At the close of this epoch, however,
the Algonkian strata had been eroded almost away, owing to its tilted
condition, so that in some places even the surface of the Archaean was
exposed, and suffered the planing-down process. Figure 1 on plate facing
page 98 is a suggestion as to the possible appearance of the rocks at this
time.
Even then, in those far-away, early ages of history, if one had been
present to measure these strata, he would have discovered the astounding
fact that, although he had measured them and found twelve thousand feet
before they began to emerge from the ocean, there were but about five
hundred feet of them left. This is one of the interesting facts in
geology, - that an observant reader can deduce so much from so little.
The twelve thousand feet deposit. "But," asks the layman, "I cannot
possibly see how, if only five hundred feet of strata are left, any one
could ever tell that there were once twelve thousand feet. If eleven
thousand five hundred feet are gone, how do you know they ever existed?"
A very reasonable question and one very easily answered. Refer to the
sketch. Let the bracket on the right show the present width of the
remaining strata, viz: five hundred feet. Now observe the tilted condition
of the remnants. To get the original height of the depositions begin with
No. 1, the stratum nearest the Archaean and measure that. Suppose it gives
us five hundred feet. No. 2 gives two hundred feet; No. 3, five hundred
feet; No. 4, one hundred and seventy-five; and so on up to No. 14. As these
strata were deposited horizontally, all we have to do is to mentally
replace them in their horizontal position. Throw the tilted strata back
again into their original condition, and by this method of measurement it
is seen that the twelve thousand feet can be made up. Figure 2, facing page
98.
Another interesting question here arises: "What became of the vast quantity
of sand and silt and pebbles that formed and were carried away during such
a gigantic process? For, think of it, eleven thousand five hundred feet of
strata, or rock, two miles high, almost three times as high a mass as the
present distance in vertical height from El Tovar to the river!
