* This chapter, while in manuscript, was read by Dr. Charles D. Walcott,
Secretary of the Smithsonian Institution and formerly Director of the
United States Geological Survey, and also by Professor Matthis, of the
Survey. It may therefore be accepted as a fairly accurate and authoritative
presentation of the geological conditions existent at the Canyon, with
their explanations, as accepted by the leading scientists of to-day.
The beginning of land. In the long ago centuries, when the world was
"without form and void," waters covered the face of the earth, and darkness
brooded over the waters. As the earth's crust began to shrink under the
water, in the process of cooling, the first masses to crumple up, to
wrinkle, were the first to arise above the surface of the vast, primeval,
shoreless ocean. They appeared as tiny islands, pinnacles, or ridges thrust
up, exactly as we see them sometimes on the coast,--hidden at high tide;
appearing again at low tide.
The Laurentian Hills. Nature had plenty of time before her, so she did not
hurry her work, and it took long centuries before there was any large
amount of land thrust up out of the bosom of the sea. The scientists are
able to tell us, with some definiteness, which came forth first. They say
that on the continent of America the earliest born land was a mass of
granitic rock in Canada,--the Laurentian Hills. The next to peer above the
surface and feel the warmth of the sun were peaks and ridges that made
islands of themselves, in what are now known as the Rocky Mountains and the
Appalachians. Now, at last, the great waves of the sea and the resistless
storms had something to play with, and they pounced down upon the land as
with tooth and claw. They rubbed and pounded, raged and smashed for a
thousand years, and then another thousand, and still another, while Mother
Earth uneasily thrust forth her rocky children out of the ocean into the
light of day. Surprised at such treatment by the storms and seas, the newly
born earth masses began to crumble and "weather." The detached fragments
slipped back, or were washed back, into the deeper or shallower parts of
the ocean, and were there tossed back and forth, pounded and ground into
sand and silt, into pebbles and boulders, while more land was slowly being
thrust out for the angry sea to work upon. Layer by layer, the ground-up
masses were deposited in the inner ocean bed, parts of which were now
practically shut off from the vast ocean beyond. How many centuries of
centuries this process continued geologists do not tell us. Time is so
vast, so long, that they cannot divide those early days into weeks, months
and years, as we now do.
The Continent is born. 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! Where has
it all gone?"
Naturally an answer to these questions is mere conjecture, as only from a
study of the facts revealed underneath the present strata, can any
comparative knowledge be gained of the conditions existent at that
prehistoric age. There may have been one river, or a score, or any number
between, and it is probable one or more rivers carried the Algonkian debris
westward and deposited it, as the Colorado River (not brought into
existence until centuries later) is now doing with the debris of the
existent strata.
Another Subsidence. Now, a new era is about to dawn. Planed and smoothed
off as they are, the Algonkian and Archaean masses are to be submerged once
more in the ever receptive ocean. A period of subsidence occurs, and the
whole area is soon hidden under the face of the sea. But, all around these
are masses, some day to be mountain peaks, that refuse to sink again into
the sea. Then the forces of the air assail them. If they cannot be drowned,
they shall be gnawed at, smitten, cut and worried by the air, the chemicals
of the atmosphere, the storms, the rain, the hail, the frost, the snow, and
thus made to feel their insignificance. Slowly or rapidly, they yielded to
this disintegrating process, and as the rocky masses broke up, they were
washed by the rills and streams into the bed of the sea, where they soon
rested upon the tilted ends of the Algonkian strata and exposed surfaces of
the Archaean masses, waiting for them.
The Deposition of the Tonto Sandstones. The wise men tell us that this
ocean was a salt sea, and that it was quite shallow while these new
sediments were being deposited. Little by little one thousand feet of the
sediments of this epoch were washed down, so that it is very likely that
the tilted strata upon which they rested slowly sank lower and lower to
accommodate them. Then, for some reason or other, there was a rest for a
while--a few hundreds or thousands of years--and the masses of sediments
became cemented into sandstone and shale, which we call the Cambrian
formation, or the Tonto sandstone. This is to be seen resting both upon the
Archaean and Algonkian from the porches of El Tovar. It is composed of
strata of dull buff, very different from the brilliant reds--almost
crimsons--of the Algonkian, and the bright reds of the strata which later
were to rest above them.
Geological Terms. What an audacious science this geology is! How ruthlessly
it wrests aside the curtain from the mystery of the past, and how glibly it
deals with thousands, millions of years, tying them up into packages, as it
were, and handing them out labeled "eras" and "periods." As usual, the
names made by the wise men are hard to pronounce, and seemingly hard to
understand. But a few minutes will take away the difficulty. They divide
the eras into four, viz.: 1, Proterozoic; 2, Paleozoic; 3, Mesozoic; 4,
Cenozoic. All these "zoics" have to do with life. Proterozoic means before
life, and signifies the rocks that contain no fossils indicative of life;
Paleozoic signifies the most ancient forms of life; Mesozoic signifies
"middle life" or those between the most ancient and the Cenozoic, or recent
forms of life. The periods are lesser divisions of the eras. In the
Proterozoic, there are two periods, viz.: the Archaean and the Algonkian.
The Paleozoic has six periods, viz.: the Cambrian, Ordovician, Silurian,
Devonian, Carboniferous and Permian. The Mesozoic era has three periods,
the Triassic, Jurassic and Cretaceous, while the Cenozoic era names five
periods,--the Eocene, Oligocene, Miocene, Pliocene and Pleistocene.
Absence of Certain Strata. To shorten our story, let me at once say that
during the periods that the Ordovician, the Silurian and the Devonian were
forming, the Grand Canyon region was either above water so that it received
none of these sediments, or, if any were deposited, they were almost
entirely removed by the weathering processes before described, ere the
region again sank into the ocean to receive the deposits of the
Carboniferous epoch.
The Carboniferous. During this latter period, more than three thousand feet
of strata were deposited. These are the most striking in appearance of all
the Canyon strata, for they reach from the Tonto shales to the rim, and
consist of three principal strata (with many smaller ones in between). The
largest is the red-wall limestone, which constitutes the base of nearly all
the architectural forms found in the Canyon, and is the thickest of all the
strata. It presents the "tallest" wall of the series. The two separate
walls, one above the other, on the top of the Canyon, as seen in the arms
of the amphitheatre at El Tovar, are the other two wide members of this
Carboniferous period. The lower is the cross-bedded sandstone, and the
upper the cherty limestone. There is a remarkable difference in the
appearance and the material of which these Carboniferous strata are formed,
and those of the East and Europe. We generally think of coal-beds--carbon
when this period is mentioned. Here there are none. In the East, in
England, and in other parts of Europe, vast marshes existed in this period,
and the rank vegetation of these marshy areas formed the coal-beds, with
which the Carboniferous there abounds. It is only by the fossils found that
the periods to which the various strata belong are determined, and the
fossils, millions of which abound in the upper limestone, are clearly of
the Carboniferous epoch.
As these strata and this period bring us to the "rim" of the Canyon, it
might be easy to imagine that the processes of uplift and subsidence, and
deposition of more strata, as far as the Canyon region is concerned, now
cease. Such, however, is not the case.
Later Strata. As we go away from the Canyon, either north or east, we find
thousands of feet more of the later depositions, and the geologists affirm
that many of these at one time may have overlaid the Canyon region. 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. 5 A. B. C. and D. of plate on page 110.
The Formation of the Canyon. Now, in imagination, let us hark back to the
day when this plateau was in the condition thus described. Nearly
everything in the way of strata has been planed down to the Carboniferous
rocks. The plateau is about at sea level. One great river already exists,
with two arms, now called the Green and the Grand, the main river some day
to be known as the Colorado. Slowly the uplift begins. It is a fairly even
process, and yet there is slightly more pressure brought to bear under the
southern portion, so that the whole mass has a slight tilt to the north.
Professor Salisbury found certain beds of rock at seven thousand eight
hundred feet above sea level at the base of the San Francisco Mountains
near Flagstaff. Forty-five miles north, at the Grand Canyon, these same
beds are only six thousand four hundred feet above sea level, while at the
Vermilion Cliffs, another forty-five miles to the north, they are but four
thousand four hundred feet above the sea.
Yet in spite of this northward tilt, when the eye ranges over the country
to the south and west, from the upper porch of El Tovar, a large area of
depression can clearly be seen, showing that surface erosion has planed
away much of the upper crust.
The Plateau Region. Now we are ready to take a look at the borders of the
plateau region. On the north, it extends into Utah, where still higher
plateaus bound it. To the west, it extends by gigantic steps into the
desert region. The main step is along the Grand Wash, near the one hundred
and fourteenth meridian. To the south, there is one glorious step, known as
the Mogollon Escarpment (locally the Red Rock Country), some three thousand
feet high, which extends for a number of miles east and west, and then
breaks down. This step and broken levels lead to the irregular lands of
Central and Southern Arizona. On the east, the plateau extends to the Echo
Cliffs beyond Marble Canyon, and as far as the ridge of the Continental
Divide, where the Santa Fe crosses the Zuni Mountains, east of Gallup, N.
M.
Present Conditions. With this general view of the great plateau in our
mind's eye, we are prepared to examine present conditions at any given spot
in the Canyon. Let us, therefore, take a seat at El Tovar, and try to read a
few pages of the stone book of Creation as opened there. Suppose all this
vast region at about sea level, and the uplift just beginning. The course
of the Colorado River is already well defined. As the uplift continues, the
cherty limestone and possibly the cross-bedded sandstone are both cut
through, as the plateau slowly emerges. Whether the process of uplift is
slow or rapid, as soon as a stratum emerges, it becomes subject to the
influences of weathering, and the uppermost strata appearing first, they
are weathered most. Hence the recession of the uppermost cliffs is greater
than that of the cliffs lower down. The differences in hardness and
resistance to weathering are alone responsible for the step-like profile of
cliffs and terraces. The lower platform owes its width entirely to the
rapid weathering and recession of the soft shales, which overlie the Tonto
sandstones. The red-wall limestone, on the other hand, remains standing out
as a cliff because of its exceeding durability.
The Faults. During the final uplift, the river cut through the Cambrian and
Algonkian strata, and into the Granite Gorge as we find it to-day, and the
process is still slowly going on. During these various periods of uplift,
there were other changes occurring. Sometimes the uplift was uneven,
certain parts of the plateau being lifted more rapidly than other parts;
then occurred breaks in the strata, called faults. There are a great number
of these faults in the plateau country, most of them crossing the Canyon
from north to south. This faulting, as is readily seen, would produce
cracks, and as the uneven uplift continued; the strata on one side of the
crack would be lifted higher than the strata on the other side. Or, the
strata on one side of the crack would be uplifted, while the other would
subside.
Bright Angel Fault. El Tovar rests directly upon the strata affected by the
Bright Angel Fault line. On going down the Bright Angel Trail, one cannot
fail to see, as he passes the tap of the cross-bedded sandstone, the break
in the strata. To the left it is fully one hundred and fifty to two hundred
feet higher than it is on the right. The same depression may be observed in
driving out to Hopi, Point, or returning. The stratum on which the road is
made should be at the same level as the stratum on which El Tovar rests.
Fault at Bass Camp. This fault is but one of a score or more on the
plateau. At Bass Camp there was a fault which displaced the strata on each
side of the "break" to the extent of four thousand feet. Later, another
fault occurred, which readjusted the displacement somewhat, and reduced the
difference to two thousand feet, yet left the evidences of the former wide
divergence. It was also during these uplift periods that the volcanic
mountains of the region came into existence, as the San Francisco Range,
Mounts Kendricks, Sitgreaves, Williams and Floyd on the south, and the
Uinkarets--Mounts Trumbull, Logan, Emma--on the north.
Lava Flows. In one place, south of Mount Emma, Powell's party saw where
vast floods of lava had flowed from it into the river. They declare that "a
stream of molten rock has run up the Canyon three or four miles, and down,
we know not how far. The whole north side, as far as we can see, is lined
with the black basalt, and high up on the opposite wall are patches of the
same material, resting on the benches, and filling old alcoves and caves,
and giving to the wall a spotted appearance." All these volcanic mountains
can be seen from Hopi or Yavapai points, near El Tovar.
The Algonkian Strata. The Algonkian strata of the Grand Canyon are by far
the most interesting; Major Powell was the first to call attention to their
existence in his report of explorations of 1869-1872, and he discusses
their origin and history as far as was possible with the small amount of
data he had at hand. Later Dr. Charles D. Walcott, his successor as
Director of the United States Geological Survey, and now the Secretary of
the Smithsonian Institution, spent a full winter in the heart of the
Canyon, especially studying the unique formations. Unique they are, for,
though found elsewhere on the earth, they are exceedingly rare, and, up to
this time; had received little study and were unknown and unnamed. The area
studied by Walcott lies at the very entrance to the Grand Canyon, near
where the Marble Canyon and Little Colorado Canyon join the main one. While
the series cross the river and are a fine feature of Red Canyon Trail, the
main study was done on the north side. Dr. Walcott thus locates the site of
his studies: "This area, between 35 degrees 57 minutes and 36 degrees 17
minutes north latitude, and between 111 degrees 47 minutes and 112 degrees
west longitude, is in the valley portion of the Canyon, between the mouth
of Marble Canyon and a point south of Vishnu's Temple, a little west of
where the Colorado River changes its course from south to southwest. It is
wholly within the greater depths of the Grand Canyon, east and southeast of
the Kaibab Plateau. The intercanyon valleys of this portion of the Grand
Canyon extend back from three to seven miles west of the river, and are
eroded in the crest of the Monoclinal fold that forms the eastern margin of
the Kaibab Plateau."
There are also interesting remnants of Algonkian directly opposite El Tovar
to the west of the Bright Angel Creek. They are easily discernible by their
brilliant geranium or vermilion color. They extend for a mile or more
westward, and rise above the Tonto sandstones, which properly belong above
them.
The most remarkable deposit and exhibition of Algonkian strata in the
Canyon, so far as known, occurs directly east of the great Kaibab Plateau,
opposite the Little Colorado River. Here there must be several, possibly
five or six thousand feet of these interesting strata, which Nature has
allowed to remain up to our day. Geologists are now investigating them more
thoroughly than ever before, and we may expect, when they publish the
reports of their labors, that our geological knowledge of the Algonkian
epoch, and possibly of other puzzling matters, will be much increased by
the light they will throw upon them.