Your National Parks, with Detailed Information for Tourists

by Enos A. Mills; Laurence Frederick Schmeckebier

A narrow ditch in the earth will widen by the caving-in of its sides. If the ditch be deepened, the caved-in matter being removed, it will continue to widen. And so it is with this cañon; the weathering or the caving-in of these walls goes ever on. The sharpness of the walls, and many of their striking features, are due to the peculiar climatic conditions that exist in this region—the short rainy seasons and long dry periods. Had there been a more even and abundant precipitation, it is probable that more vegetation would have been produced, which would have had a marked influence upon the walls, giving them a more rounded and less interesting form.

The cañon broadens with the years. Cut narrow by the river, it has gradually widened by the caving-in of the walls. If it had remained as the river cut it, it would now be as narrow at the top as it is in the bottom—a cañon about a mile deep, only a few hundred feet wide, and with perpendicular walls. As it is, the walls rise through a series of shattered inclines, precipitous slopes and terraces, with here and there a vertical section.

Well may the Cañon of the Colorado be called the greatest inanimate wonder in the world. Written in the exposed and remaining rock-strata through which the river has cut its way is a wonderful story of the past, a marvelous and splendid romance. At an enormously remote time the Grand Cañon plateau rose from the primeval sea. After long exposure and great weathering it sank back, remained submerged for ages, and thousands of feet of strata were deposited upon it. Again it emerged, was exposed "a million years and a day," during which æon thousands of feet of strata were eroded away. Again it went down into the sea, and upon it were piled thousands of feet of additional strata. A fourth time it rose slowly above the water. As this plateau was rising, its surface was acted upon by the elements. The part of the plateau surrounding the Grand Cañon proper was the scene of repeated volcanic action and earthquake disturbance. Here the strata have been subjected to repeated faultings, heavings, tiltings, and lava-flows. This uplift imprisoned an enormous Eocene lake that occupied much of what is now the Colorado River basin. This lake the river drained. The drainage was quite probably caused by the fact that the eastern part of the territory was uplifted higher than the western. The drainage-system of the Colorado River, as we now know it, began at that time to take on form and its waters started to cut the cañon. This crude outline covers cycling ages, and probably represents millions of years.

Through several thousand years the plateau slowly rose, and all this time the river was gradually cutting its way down into it. Finally the plateau ceased to rise and long remained at a standstill. After cutting down to its first base level, the river had so little fall that its waters, overladen with débris, ceased deepening the channel. The widening of the cañon went steadily on. Again the plateau slowly rose, perhaps two thousand feet. This uplift increased the fall of the river and again set it to deepening its channel, a work it is still doing.

The waters of the Colorado River are heavily laden with sediment. During the ages it has transported an inconceivable bulk of eroded material to the ocean. Much of this has come from its three hundred thousand square miles of mountainous drainage basin and all the material which formerly occupied the vast spaces of its numerous cañons. Continual caving of the walls compels the river to spend most of its time and energy in breaking up this débris and carrying it forward to the sea. This condition has existed for thousands of years.

It should be borne in mind that the transporting capacity of running water varies as the sixth power of its velocity. Therefore when a stream doubles its velocity it is competent to move particles sixty-four times greater than before. If its rate of flow is trebled, its transporting power is increased seven hundred and twenty-nine times. This goes to explain the frightful havoc of streams at times of flood.

The tributary streams of the Colorado come from arid regions and from the deserts, and are subject to sudden violent cloud-bursts and enormous floods. Though these are of short duration, they are of tremendous force. Earthy matter, rocky débris, and ofttimes hundreds of trees are swept along by the waters that rush in from side cañons like an awful avalanche. Lodged driftwood over one hundred feet above normal river-level tells of the magnitude of these wild floods.

Where a stream has all the load of any given degree of fineness that it is capable of carrying, the entire energy of the descending water is consumed by the transportation of the water and its burden, so that none is applied to erosion. If it has an excess of load, its velocity is thereby lessened and its power to transport is diminished; consequently a part of its load is dropped. If it has less than a full load, it is in a condition to receive more, which it eagerly does. Thereby its bed is swept clean, and then only does erosion become possible. Thus it is seen that the work of transportation may at times monopolize the entire energy of a stream to the exclusion of erosion; or the two works may be carried forward at the same time.

The rapidity of erosion depends upon the hardness, size, and number of the fragments in the flowing water, upon the durability of the stream-bed, and upon the velocity of the current, the element of velocity being of double importance, since it determines not only the size but the speed of the particle with which it works. Transportation is favored by an increased water-supply as much as by increased declivity, because when a stream increases in volume the increase in its velocity outruns the increase in volume, and its transporting power is correspondingly augmented. It is due to this that a stream which is subject to floods—periodical or otherwise—has a much greater transporting power than it could possess were its total water-supply evenly distributed throughout the year.

During one period of volcanic activity the focus of lava-flows into the cañon was at Lava Falls. A number of lava-streams burst directly into the cañon through the walls, while several flows poured their fiery floods over the brink. What a wild and spectacular condition existed while the river, deep in the cañon, received these tributaries of liquid fire! When the flow ceased, the cañon for sixty miles was filled with lava to the depth of about five hundred feet. The lava cooled, and in time was eroded away. The records of this spectacular story are still easily read.