WHAT MADE GRAND CANYON?

By Dr. Chas. N. Gould
Regional Geologist.

Nowhere on this whirling planet may man see a better demonstration of Nature's three fundamental processes-deposition, elevation, and erosion-than at Grand Canyon National Park. First, the rocks have been deposited or laid down as layers, one above another, in the bottoms of long-gone, prehistoric seas; second, these rock-layers have been elevated or raised by some tremendous force above their original position; and, third, the rocks have been eroded or worn away and their fragments carried to some other place.

These three processes are eternal and fundamenetal-always in operation, never ceasing, never completed. From the time when "the morning stars sang together", even until time shall be no more, without haste and without rest, these three processes have been constantly at work, making over and reshaping this old earth of ours. But so slowly, so quiety has this work been accomplished that we, "denizens of a second-rate planet belonging to a fourth-rate and moribund star", are rarely conscious of it. We each play our own little part in the drama of life, and leave the stage to others, taking small account of the universal drama which goes on all about us.

Grand Canyon is 200 miles long, a mile deep, and averages 10 miles in width. There is nothing else like it anywhere. But it didn't just happen; neither has it always been there. The story of the development of Grand Canyon has been written in the rocks so that he who runs may read. All that is needed is the seeing eye and the understanding mind.

When you mount a mule and take the Bright Angel trail from the canyon rim, winding down to the Colorado River, you will see, if your eyes be open, the rock layers that make up the walls of the canyon. The three most abundant kinds of stratified rocks: shales, sandstones, and limestones-are much in evidence, layer after layer, laying level one above another, some hard, some soft, with a total combined thickness of 3,000 feet. In these rock-layers there are fossils, or evidence of extinct life, showing the progressive development from primitive one-celled forms to large lizard-like animals. Finally you come to the inner gorge, and still the trail loads down across another kind of rock. These are all very hard rocks, granites and gneisses and schists, not arranged in level beds or layers, but crumpled, twisted, and contorted, in all sorts of shapes. And so, at last, to the bridge over the Colorado River, a muddy, turbulent stream, flowing swiftly between precipitous cliffs, rushing madly on its way to the western ocean.

GRANITE AT BOTTOM OF GRAND CANYON.

Four of the five major divisions of geologic time are represented along the canyon wall. Within the inner gorge we find granites and other associated rocks belonging to the Archaeozoic and proterozoic eras. This is the original earth-stuff, the "basal complex", the material from which all other rocks have been formed, that goes downward to the center of the earth. The level-lying beds that constitute the upper 3,000 feet of the canyon wall belong chiefly to the Paleozoic era, including Cambrian, Devonian Mississippians, and Permian beds. At one place, there are red sandstones and shales, part of the Moenkopi formation, the lowest member of the Triassic, of the Mesozoic era.

Now these things, which I have attempted to describe so briefly, are very obvious. We can see the rocks, and we can feel them. But constantly our minds are inquiring: how, why, when, what caused all this? The history of Grand Canyon is long-very long. The granite now being exposed in the bottom of the inner gorge is among the oldest rock exposed anywhere on the surface of the earth. How many years? Oh, say eight hundred million to one thousand million years. Nobody knows. Anyhow, it happened before your time, or mine. So why worry? It really doesn't matter.

Then throughout the unnumbered ages the geologic column was slowly built up. Shales, sandstones, and limestones, layer upon layer, were washed in from surrounding land masses and laid down on the bottom of long-departed oceans, or along vanished shore lines. There are eleven different formations or layers exposed in the canyon walls. Some geologists believe that one of these formations, the Coconino sandstone, may have been deposited chiefly as desert sand dunes. Eventually the layer cake was done. The rock layers had all been deposited, one above another. Then the seas drained away, and the country stood as dry land. Rivers began flowing across the surface of this land. Water falling as rain in distant mountains formed small rivulets, which came together forming larger and larger streams. These finally united into a large river, the second largest in the United States, which today we call the Colorado. This stream, taking its rise along the back bone of North America, started on its way to the Pacific. It flowed in a general southwestern course, dodging hills, keeping to the lowest channel, for water runs down hill, you know, cutting its way through soft rocks, avoiding the harder ledges, often twisting about like a a tortured snake, and acting as a normal, well-behaved river is supposed to act. The general course of the Colorado, all the way from Long's Peak to the Gulf of California, was established in the dim, dead days beyond recall.

Then something happened. Near the middle course of the Colorado the land surface began "acting up". It wouldn't stay put. Some great internal force of Nature began raising the land; something like a giant blister, right across the well-established course of the Colorado River. Imagine an inverted saucer 100 miles in diameter. Geologists call this bulge the Kaibab Dome, or the Kaibab Plateau. Sometimes we say the Kaibab Uplift.

ROCK LAYERS IN GRAND CANYON WALL.

What could a hard-working river do when things went haywire? Two things: It might either peacefully abandon its course without a fight and flow around the Dome or it might buckle down to cut its way across. If the elevation of the Dome had been rapid, undoubtedly the river would have been deflected either to the north or to the south and its lower course today would have been many hundreds of miles away from its old channel. But, as it happened the land rose slowly, very, very slowly; just how fast we do not know, but probably only a few inches a century. So that the river in its down-cutting has just about been able to keep pace with the elevation of the land. Or, to say it differently, the water in the channel of the Colorado River in Grand Canyon was probably never a great deal higher above sea level than it is to day. As throughout the ages the Kaibab Plateau has slowly risen, an inch at a time, just so slowly has the river succeeded in cutting its way downward. In this cutting it has been aided by the sand, pebbles and boulders which are carried in times of flood. These tools of erosion gouge and grind and gnaw and rub and abrade the solid rocks along the banks, and slowly but surely wear them away, constantly widening and deepening the channel.

The Colorado is not a patient, quiet, kindly stream, as is the Mississippi or the Ohio, flowing in gentle meanders through flat valleys. Its disposition has been ruined, and it is today a very impatient river. On its way through the canyon it growls and roars and froths. It tumbles over rapids, throwing spray into the air, and slaps at its banks. In every way possible the Colorado seems to protest at being imprisoned between high walls. But the grim, unheeding walls stand sheer, and its turbulent course continues until, finally, in man-made Lake Mead, extending a hundred miles above Boulder Dam, the troubled waters come to rest.

And so, we may see at Grand Canyon a clear-cut demonstration of Mother Nature's three eternal processes: deposition, elevation, and erosion. It is textbook geology, simple and easy to understand. From the canyon rim, or along the trail, or looking up from the bottom, the rock layers "leap" to the eye. The most unobservant person cannot fail to see them. There is nothing else to see. And so with the Kaibab Uplift. If we know where to look, it is easy to see the outline of the great Dome. Perhaps the best place is along one of the highways on the east side of the Uplift. On the road from Cameron to Desert View south of the Colorado; or between Houserock Valley and Jacobs Lake north of the river, one may see the ledges of limestone, one above another, all dipping to the east along the east flank of the Kaibab Dome. And along the road leading north from Jacobs Lake to Kanab, Utah, the ledges dip sharply down the north slope of the dome. The north rim of Grand Canyon is 1,000 feet higher than the south rim, although the same Kaibab limestone forms the rim rock in both places. The highest point of the Kaibab Dome is near the north entrance to the park, ten miles north of the lodge on the north

Great men of American Science have worked in Grand Canyon. As early as 1857 Dr. J. S. Newberry, afterward of Columbia University, prepared the first geological report on Grand Canyon, in which he set forth the geologic importance of the area.

In 1869 a party under the direction of one-armed Major John Wesley Powell made the first boat trip down the Colorado River and proposed many of the striking names which have since become classic, such as Dirty Devil, Bright Angel, and God's Pocket. Powell was afterwards Director of the United States Geological Survey and at the same time Director of the Bureau of American Ethnology. In the latter capacity he did much to lay the foundations of Southwestern archaeology. There is a monument to Powell on the south rim of Grand Canyon.

Sixty years ago Captain C. E. Dutton, one of Powell's associates, published the first monograph on Grand Canyon. The versatile W. H. Holmes, geologist, ethnologist, and artist, contemporary of Powell and Dutton, succeeded Powell as Director of the Bureau of American Ethnology. Holmes, it was, who made the noted pen sketches of Grand Canyon.

During the early 80's Dr. Charles D. Walcott, Powell's successor as Director of the United States Geological Survey, spent an entire winter in the eastern Grand Canyon, making important contributions to our knowledge of Cambrian and Algonkian rocks and on the subject of the oldest life.

David White, whose ashes repose in the cemetery on the south rim, one of the great paleobotanists of America, first brought to public attention, through his discoveries and writings, the wealth of interesting fossil plant remains buried in various layers of the Grand Canyon walls.

Truly, there were "giants in those days".

The outstanding fact about Grand Canyon is that the elevation of the dome and the down-cutting of the stream have been contemporaneous. In most cases the rocks have first been elevated, and then the processes of erosion have begun. Nature's tools: rain, running water, wind, frost, heat, and chemical agencies, working together, break down the rocks and carry them away. In this manner, most land forms have been produced. Hills, valleys, cliffs, canyons, mesas, buttes, and the hundreds of different erosion forms, have been shaped chiefly by the action of the agents of erosion on land already elevated. This is the ordinary procedure, as for instance, in the Black Hills of South Dakota; the Ozarks of Missouri; or the Arbuckle Mountains of Oklahoma, to mention only a few.

But in the case of Grand Canyon, the two processes are going on at the same time, All available evidence points to the fact that the Kaibab Plateau is still rising - very slowly it is true, but rising just the same. We knew for a certainty that the Colorado is still sawing its way athwart the slowly-rising dome.