THE second period of the Mesozoic era, or middle age, is called Jurassic, a name taken from the Jura Mountains, in Europe, where these rocks were studied. During this period were formed the rocks which make the Plateau country the natural picture gallery of the world. These rocks are perhaps best exhibited in Zion National Park, in southern Utah.
Zion National Park
Zion Canyon is almost unique among natural wonders. It is a narrow gorge cut in highly colored rock between nearly vertical walls about 3,000 feet high (Plate XXIII).
Canyons form a group of scenic landscapes that are second in impressiveness only to those formed by mountains. Grand Canyon is the most impressive of the group, and Zion Canyon is one of its tributaries. Of all the stream-cut gorges, Zion Canyon is one of the most conspicuous. Niagara Gorge seems impressive as we gaze into its depths, but fifteen Niagaras might be placed in Zion Canyon, one above the other, before they reached the rim. The splendidly colored rocks carved by natural forces in impressive outlines; the great walls rising in astonishing grandeur; the deep, narrow trench cut by the little stream working through untold agesthey cannot be described, they must be seen.
Zion Canyon is in the southeastern part of the high plateaus of Utah and is notable for many features of unusual geologic and geographic interest. It also has archeologic interest, for here are found the remains of prehistoric races of America and of ancestral Indian tribes. Its geologic features include craters of extinct volcanoes, fossiliferous deposits, and brilliantly colored strata, among which are some that are believed to be the best representations in the world of a rare type of sedimentation. The features of geographic interest include a labyrinth of remarkable canyons that have highly ornate and beautifully colored walls.
The principal canyon in Zion National Park is occupied by the North Fork of Virgin River. It is called Mukuntuweap by some, and Zion Canyon by others. The name Zion Canyon is employed much more frequently than Mukuntuweap, and it was in use among the settlers of Utah for several years before Major J. W. Powell described the canyon under the Indian name.
The rocks that we saw in the Petrified Forest appear also in Zion Canyon, but here they are overlain by a massive red sandstone, which is one of the dominating features in the marvelous scenery of the plateau country. This sandstone (Plate XXIV) is more than 2,000 feet thick and is brilliantly colored from top to bottom. It has been called the Vermilion Cliff sandstone because it forms Vermilion Cliffs, east of this canyon. It is overlain by a white sandstone about 1,000 feet thick, the two sandstones together forming walls that rise almost vertically to heights of more than half a mile.
Temples of the Virgin
Among the conspicuous objects of interest in Zion Canyon are two enormous natural structures that have been called the Temples of the Virgin (Figure 2). These consist of the richly red Vermilion Cliff sandstone below and the White Cliff sandstone above. Some idea of the magnitude and glory of these structures is conveyed by the name temples.
It was the western Temple that served as a landmark to guide Major Powell and his party across the desert from the mouth of Virgin River to Salt Lake City after they had completed their remarkable exploration of Grand Canyon. His account seems to show that the spires of the Temple were recognized from a distance of 60 or 70 miles.
The eastern Temple of the Virgin is as imposing as the western Temple and in some respects more fascinating, but it does not appear to as good advantage from the entrance to the canyon.
These temples have justly been regarded as preeminent among forms of natural architecture. In comparing them with the noble and wonderfully ornate buttesthe so-called templesin the Grand Canyon, Major Clarence Dutton, an early authority on the plateau region, acknowledged that for "nobility of form, beauty of decoration, and splendor of color, the Temples of the Virgin must . . . be awarded the palm."
The temples are great remnants of an old plateauthat is, they are parts of it that have not been worn down. The beds of rock of which they are formed were once connected across the canyon that now separates them and extended far to the south and west over a wide area. Their original extent will probably never be known, for with the elevation of the plateau region they were in large part eroded and carried away, and it is their remnants that now form the glorious scenery of Zion Canyon.
In his description of the Vermilion Cliffs near Zion Canyon, Major Dutton advises that "We must be frugal of adjectives lest . . . we find their force and meaning exhausted," and he truthfully states that the ornate sculpture and the rich coloring of the cliff walls "might justify very exalted language of description." He says:
There are portions of the Vermilion Cliffs which in some respects lay hold of the sensibilities with a force not much less overwhelming than the majesty of the Grand Canyon; not in the same way, not by virtue of the same elements of power and impressiveness, but in a way of their own and by attributes of their own. In mass and grandeur and in the extent of the display there is no comparison; it would be like comparing a private picture gallery containing a few priceless treasures with the wealth of art in the Vatican or Louvre.
The profile of the Vermilion Cliffs is very complex, though conforming to a definite type and made up of simple elements. Though it varies much in different localities it never loses its typical character. It consists of a series of vertical ledges rising tier above tier, story above story, with intervening slopes covered with talus, through which the beds project their fretted edges. The stratification is always revealed with perfect distinctness and is even emphasized by the peculiar weathering. . . . Where the profiles are thrown well into view the vertical lines, which bound the faces of the ledges, are quite perpendicular and straight, while the lines of the intervening slopes are feebly concave. . . . This effect is much enhanced by the manner in which the wall advances in promontories or recedes in alcoves, and by the wings and gables with sharp comers and Mansard roofs jutting out from every lateral face where there is the least danger of blankness or monotony. . . . This sandstone has many strong features and yet they elude description. One point, however, may be seized upon, and that is a series of nearly vertical joints with which the mass is everywhere riven. The fissures thus produced have been slowly enlarged by weathering, and down the face of every escarpment run the dark shadows of these rifts. They reach often from top to bottom of the mass and penetrate deeply its recesses. Wherever this great member forms the entablatureand west of Pipe Spring it usually does soits crest is uneven and presents towers and buttresses produced by the widening of these cracks. Near Short Creek [about 10 miles southeast of Rockville] it breaks into lofty truncated towers of great beauty and grandeur, with strongly emphasized vertical lines and decorations suggestive of cathedral architecture on a colossal scale. Still loftier and more ornate become the structures as we approach the Virgin. At length they reach the sublime. The altitudes increase until they approach 2000 feet above the plain. The wall is recessed with large amphitheatres, buttressed with huge spurs, and decorated with towers and pinnacles. Here, too, for the first time along their westward trend the Vermilion Cliffs send off buttes. And giant buttes they verily are, rearing their unassailable summits into the domain of the clouds, rich with the aspiring forms of Gothic type, and flinging back in red and purple the intense sunlight poured over them. Could the imagination blanch these colors, it might compare them with vast icebergs, rent from the front of a glacier and floating majestically out to sea, only here it is the parent mass that recedes, melting away through the ages, while its offspring stands still; yet the analogy would be a feeble one, for the buttes are grander, more definite in form, and many times loftier. But the climax of this scenery is still beyond.
Late in the autumn of 1880 I rode along the base of Vermilion Cliff from Kanab to the Virgin, having the esteemed companionship of Mr. Holmes. We had spent the summer and most of the autumn among the cones of the Uinkaret, in the dreamy parks and forests of the Kaibab, and in the solitudes of the intervening desert; and our sensibilities had been somewhat overtasked by the scenery of the Grand Canyon. It seemed to us that all grandeur and beauty thereafter beheld must be mentally projected against the recollection of those scenes, and be dwarfed into commonplace by the comparison; but as we moved onward the walls increased in altitude, in animation, and in power. At length the towers of Short Creek burst into view, and, beyond, the great cliff in long perspective thrusting out into the desert plain its gables and spurs. . . .
As we moved northward from Short Creek we had frequent opportunities to admire these cliffs and buttes, with the conviction that they were revealed to us in their real magnitudes and in their true relations. They awakened an enthusiasm more vivid than we had anticipated, and one which the recollection of far grander scenes did not dispel. At length the trail descended into a shallow basin, where a low ledge of sandstone, immediately upon the right, shut them out from view; but as we mounted the opposite rim a new scene, grander and more beautiful than before, suddenly broke upon us. The cliff again appeared, presenting the heavy sandstone member in a sheer wall nearly a thousand feet high, with a steep talus beneath it of eleven or twelve hundred feet more. Wide alcoves receded far back into the mass and in their depths the clouds floated. Long, sharp spurs plunged swiftly down, thrusting their monstrous buttresses into the plain below, and sending up pinnacles and towers along the knife edges. But the controlling object was a great butte which sprang into view immediately before us, and which the salient of the wall had hitherto masked. Upon a pedestal two miles long and 1,000 feet high, richly decorated with horizontal mouldings, rose four towers highly suggestive of cathedral architecture. Their altitude above the plain was estimated at about 1,800 feet. They were separated by vertical clefts made by the enlargement of the joints, and many smaller clefts extending from the summits to the pedestal carved the turrets into tapering buttresses, which gave a graceful, aspiring effect, with a remarkable definiteness, to the forms. We named it Smithsonian Butte, and it was decided that a sketch should be made of it; but in a few moments the plan was abandoned or forgotten, for over a notch or saddle formed by a low isthmus which connected the butte with the principal mesa there sailed slowly and majestically into view, as we rode along, a wonderful object. Deeply moved, we paused a moment to contemplate it, and then abandoning the trail we rode rapidly toward the notch, beyond which it soon sank out of sight. In an hour's time we reached the crest of the isthmus, and in an instant there flashed before us a scene never to be forgotten. In coming time it will, I believe, take rank with a very small number of spectacles each of which will, in its own way, be regarded as the most exquisite of its kind which the world discloses. The scene before us was The Temples and Towers of the Virgin.
At our feet the surface drops down by cliff and talus 1,200 feet upon a broad and rugged plain cut by narrow canyons. The slopes, the winding ledges, the bosses of projecting rock, the naked, scanty soil, display colors which are truly amazing. Chocolate, maroon, purple, lavender, magenta, with broad bands of toned white, are laid in horizontal belts, strongly contrasting with each other, and the ever-varying slope of the surface cuts across them capriciously, so that the sharply defined belts wind about like the contours of a map. From right to left across the further foreground of the picture stretches the inner canyon of the Virgin, about 700 feet in depth and here of considerable width. Its bottom is for the most part unseen, but in one place is disclosed by a turn in its course, showing the vivid green of vegetation. Across the canyon, and rather more than a mile and a half beyond it, stands the central and commanding object of the picture, the western temple, rising 4,000 feet above the river. Its glorious summit was the object we had seen an hour before, and now the matchless beauty and majesty of its vast mass is all before us. Yet it is only the central object of a mighty throne of structures wrought up to the same exalted style and filling up the entire panorama. Right opposite us are the two principal forks of the Virgin, the Parunuweap coming from the right or east, and the Mukuntuweap or Little Zion Valley, descending towards us from the north. The Parunuweap is seen emerging on the extreme right through a stupendous gateway and chasm in the Triassic terrace, nearly 3,000 feet in depth. The further wall of this canyon, at the opening of the gateway, quickly swings northward at a right angle and becomes the eastern wall of Little Zion Valley. As it sweeps down the Parunuweap it breaks into great pediments, covered all over with the richest carving. The effect is much like that which the architect of the Milan Cathedral appears to have designed, though here it is vividly suggested rather than fully realized, as an artist painting in the "broad style" suggests many things without actually drawing them. The sumptuous, bewildering, mazy effect is all there, but when we attempt to analyze it in detail it eludes us. The flank of the wall receding up the Mukuntuweap is for a mile or two similarly decorated but soon breaks into new forms, much more impressive and wonderful. A row of towers half a mile high is quarried out of the palisade, and stands well advanced from its face. There is an eloquence to their forms which stirs the imagination with a singular power, and kindles in the mind of the dullest observer a glowing response. Just behind them, rising a thousand feet higher, is the eastern temple, crowned with a cylindric dome of white sandstone; but since it is, in many respects, a repetition of the nearer western temple, we may turn our attention to the latter. Directly in front of us a complex group of white towers, springing from a central pile, mounts upwards to the clouds. Out of their midst, and high over all, rises a dome-like mass, which dominates the entire landscape. It is almost pure white, with brilliant streaks of carmine descending its vertical walls. At the summit it is truncated, and a flat tablet is laid upon the top, showing its edge of deep red. It is impossible to liken this object to any familiar shape, for it resembles none. Yet its shape is far from being indefinite; on the contrary it has a definiteness and individuality which extort an exclamation of surprise when first beheld. There is no name provided for such an object, nor is it worth while to invent one. Call it a dome; not because it has the ordinary shape of such a structure, but because it performs the function of a dome. . . .
Nothing can exceed the wondrous beauty of Little Zion Valley, which separates the two temples and their respective groups of towers. Nor are these the only sublime structures which look down into its depths, for similar ones are seen on either hand along its receding vista until a turn in the course carries the valley out of sight. In its proportions it is about equal to Yosemite, but in the nobility and beauty of the sculptures there is no comparison.
Gates of Zion
On entering Zion Canyon we pass what have been called the Gates of Zion and three wonderful monuments, which some have called the Three Buttes and others the Three Patriarchs (Plate XXV). The region in which they stand was called Rock-Rovers Land by the Indians.
According to Major Powell, this was believed by the Indians to be the home of spirits called Tú-nu-ur-gwait'-si-gaip, or Rock-Rovers. It was said that these spirits once kindled a fire on one of the spires, the walls of which are so precipitous that no man can climb them. Although the Indians entered the canyon occasionally in pursuit of game, they could not be persuaded to spend the night there, for they believed that evil spirits lurked in the dark recesses to punish intruders.
On passing the Gates of Zion one enters an enormous trench whose walls rise almost vertically more than 3,000 feet. On the west is the Streaked Wall, so called because the face of the upper part of the cliff, formed by the White Cliff sandstone, is streaked here and there by wash leached from the highly colored rocks above (Plate XXIV). On the east is the Brown Wall, upon which stand three prominent pinnacles. These splendid monuments may be seen to best advantage early in the afternoon, when their west faces are lighted by the declining sun, but before the shadows have crept far from the eastern wall of the canyon.
Within the canyon are scenes too numerous to mention and too wonderful to express in words. The Great Organ is there, and the Sphinx, and the impressive mass called the Angels' Landing, and the still more magnificent pile called the Great White Throne (Plate XXIV); and last but by no means least, the Narrows, pictured in Plate XXIII.
Although the Narrows is a place visited by few people, it has been an object of wonder and admiration for many years, and many have gazed into it from a safe distance. In 1872 Doctor G. K. Gilbert entered Zion Canyon from the north through this narrow defile. From his account, published three years later, I quote as follows:
The north fork . . . traverses, in the most wonderful defile it has been my fortune to behold, the massive sandstones of the Gray [White of other writers] and Vermilion Cliffs, here combined in a single undistinguishable body, certainly not less than 2,000 feet in depth. At the head of "The Narrows" the top of this bed is at the water's edge; and, as the strata rise and the stream descends southward, the height of the cañon-walls gradually increases until it includes the entire mass of sandstone. At the water's edge here the walls are perpendicular, but in the deeper parts they open out toward the top. As we entered and found our outlook of sky contractedas we had never before seen it between cañon cliffsI measured the aperture above, and found it 35°. We had thought this a minimum, but soon discovered our error. Nearer and nearer the walls approached, and our strip of blue narrowed down to 20°, then 10°, and at last was even intercepted by the overhanging rocks. There was, perhaps, no point from which, neither forward nor backward, we could discover a patch of sky, but many times our upward view was completely cut off by the interlocking of the walls, which, remaining nearly parallel to each other, warped in and out as they ascended. For a number of miles the bottom of the cleft averages 30 feet in width, contracting frequently to 20, and in many places is entirely occupied by the stream, even at its low stage. Near the head of the cañon it is covered by sand and bowlders of sandstone, worn and fallen from the walls, and these continue throughout; but at a certain point a tributary gorge from the west brings in basaltic bowlders from some extinct volcano on the mesa above, and they abound to the end of the gorge. The superior toughness of the basalt enables it to withstand the shocks that rapidly crush the sandstone, and, though its supply must be far less, its rounded bowlders almost exclusively pave the river-bed for many miles. The course of the gorge is exceedingly tortuous, and, though our general direction in traversing it was southward, we yet journeyed toward all points of the compass in turn, our view in advance being usually limited at a few rods' distance by an angle. The side cañons all partake of the character of the main, but, being worn by smaller streams, are narrower, and their bottoms are of steeper grade. Many of them at their mouths are not cut so deep as the one we followed, and discharge at various heights above the flyer. . . . As a monument of denudation this chasm is an exampleand a peculiarly differentiated exampleof downward erosion by sand-bearing water. The principle on which the cutting depends is almost identical with that of the marble-saw, but the sand grains, instead of being imbedded in rigid iron, are carried by a flexible stream of water. By gravity they have been held against the bottom of the cut, so that they should make it vertical, but the current has carried them, in places, against one side or the other, and so far modified the influence of gravity that the cut undulates somewhat in its vertical section, as well as in its horizontal. The diagram represents an extreme but not exaggerated case of this departure from verticality, and, at the same time, shows the relation of the depth to the width of the cañon, where it is narrowest. The form at top is necessarily hypothetical; from our subterranean position we could form little idea of it.
Rainbow Bridge, called also Nonnezoshe (Plate XXVI), is a huge but graceful arch of sandstone, so high that it might span the dome of the National Capitol. This arch rises 309 feet above the bed of Bridge Creek and has a span of 278 feet. The sandstone at the top of the arch is 42 feet thick and 33 feet wide.
The bridge stands in a canyon so large that the great arch seems dwarfed. As Bridge Creek is a tributary of Colorado River, Rainbow Bridge belongs in the Grand Canyon group of natural wonders.
Here, as in many another place, one of the first questions asked is, What made it? According to H. D. Miser and others the bridge is a product of normal erosion. There is nothing supernormal about it. There are many similar natural bridges, but Rainbow Bridge commands special attention because of its large size.
The great arch was carved by the stream which now flows under it, in relatively recent time. To be sure, it has stood for untold ages as measured in terms of human life. But what is the lifetime of a man as compared with a geologic age? Bridge Canyon is young. The creek that formed it may have begun the work a million years agoperhaps two millions: who can say? As it cut slowly downward, it swung from side to side wearing away the rocks, as illustrated in the accompanying diagrammatic map (Fig. 3).
Hills Only Relatively Everlasting
The rock spur at the bridge was undercut from both sides by the stream in its meandering course, as illustrated in Figure 3, until this stream broke through and took the shorter route underneath the newly formed arch.
As the stream continues to work during the coming ages, all vestiges of this great arch may be swept away and similar bridges may be formed in other places, just as scores of other arches were doubtless formed and swept away while Bridge Canyon was being cut.
But the observer should not hold the mistaken notion that natural wonders like the great stone arch are eternal. The "everlasting hills" are everlasting only in a relative sense. In comparison with human life they seem enduring. In comparison with the life of the earth their origin and destruction are mere incidents.
The white sandstone at the rim of Zion Canyon occurs widely throughout the plateau province and forms many of the scenic features of this province. In Rainbow Bridge National Monument, in southern Utah, it forms what is probably the most impressive natural bridge in the world.
This bridge was viewed by white men for the first time on August 14, 1909, when W. B. Douglas and others reached it under the guidance of two Piute Indians. In the following year the Rainbow Bridge National Monument was created by proclamation of President Taft.
Only a few of the living Indians knew of the existence of Rainbow Bridge prior to 1909, but it may have been an object of worship to the ancestors of these Indians. White Horse, a Navajo Indian who accompanied Mr. Douglas, refused, after passing under the bridge, to retrace his steps, because he had "evidently forgotten the prayer that the Navajos believe they are required to utter under penalty of death before they retrace their steps beneath an arch which to them represents the rainbow or sun path." White Horse therefore climbed laboriously around the end of the bridge rather than return by the easy path underneath it.
Story of the Jurassic Rocks
As the rocks of the Jurassic periodthe middle period of the Mesozoic eraform so many of the scenic wonders of the West, it may be appropriate to sketch here the story of their origin. To understand this story we must reconstruct in imagination the geographic conditions during several successive periods of time and must envisage the progressive changes in the distribution of land and water and of deserts and swamps. We must realize that sea waves once rolled where great snow capped peaks now stand, and that, in place of the sandy deserts of the present day, sluggish streams once meandered over broad, swampy lowlands.
The succession of events that are essential to this understanding begins with a time in the Carboniferous or Coal Measures period when the sea covered the region where the high plateaus and mountains now stand. This sea was expelled when the ancestors of the present Rocky Mountains rose east of the plateau region. For long ages these highlands withstood the elements, but they were finally torn down and swept away.
The débris from these mountains accumulated as the great beds of red sandstone and shale which make much of the gorgeous scenery in the foothills of the Rocky Mountains. The western base of these mountains was washed in early Triassic time by a sea which extended from the Pacific Ocean across the site of Grand Canyon.
This sea was finally filled and in its place was developed a broad, gently sloping plain, over which rivers meandered, bringing great tree trunks from the highlands and burying them in the sand and mud. Some of these may now be seen in the Petrified Forests of Arizona, already described.
Before the ancestral Rocky Mountains had entirely disappeared, other lands were elevated farther to the west, between them and the Pacific Ocean, and on these new lands mountains were thrown up. Probably these new mountains were high, for a desert was formed east of them, perhaps for the same reason that a desert now lies east of the High Sierra of California. The moisture from the Pacific was precipitated on these mountains and the streams carried a part of the rock waste eastward into the desert, where the winds reworked it, piling the sand into dunes which are now recognized in a fossil state in the rocks of Zion Canyon and other places.
In attempting to understand the geography of this region during the Jurassic period it is essential to realize that the conditions affecting the deposition of sediments in Triassic time were far different from those that prevailed in the Jurassic. The ancestral Rocky Mountains in Colorado, which had been highlands in Permian and Triassic time, were now worn down to rolling plains and low hills. It is equally important to realize that a desert exists only where the air contains little moisture. The present desert of western America is due in part to the high mountains near the Pacific Coast, which cool the moisture-laden winds and precipitate their moisture. In the same way the high mountains of the western continent of Jurassic time probably produced a desert, for the great mass of sandstone that makes some of the remarkable scenery of the canyon country originated as desert sand.
However, this Jurassic desert was confined to western America. Other parts of the world teemed with animal life during the Jurassic period. The reptiles were highly developed and were the dominant creatures of the time. There were a few marsupials or mammals of the lowest types, which differed little from the reptiles. A few primitive mammals had existed in the Triassic period, but their development into the higher forms with which we are familiar was slow. Those of the Jurassic period were probably similar to the modern egg-laying mammals of Australia.
The First Bird
The first bird that we know anything about lived in Jurassic time. The discovery of its remains was one of the spectacular finds in paleontology, for it appealed strongly to the popular imagination. This peculiar creature, Archæopteryx, had many distinctly reptilian characteristics and is regarded as a connecting link between reptiles and modern birds. The first indication of the existence of such a bird was found in 1860, when the impression of a single feather was found in the lithographic limestone of Solenhofen. A year later a nearly complete skeleton was discovered near Eichstadt.
Archæopteryx was about as large as a domestic pigeon. It had a small head, large eyes, nostrils situated well forward, and jaws set with many small teeth. It had no beak like that of modern birds. Its body was long and slender and lacked the large breast muscles of modern birds, which make them strong fliers.
Near the end of the Jurassic period a world-wide revolution occurredsome earth disturbance which caused the sea to retire from western America. With the succeeding period began a new order of events. The desert of early Jurassic time had been flooded by the sea in the later part of the period, and this sea in its turn retired, yielding the stage for other scenes.
On the floor abandoned by the Jurassic sea and on the surrounding lowlands great swamps were formed (Plate XXVII, A) and sluggish streams followed winding, shifting courses to the sea. Temporary lakes were formed in some places, and many bayous and lagoons. Through long ages the meandering streams swung from side to side, slowly filling the lakes with sand and the marshes with mud. This swampy area extended from Utah to Kansas and from New Mexico to Montana. It is now represented by rocks that the geologist calls the Morrison formation.
In the great swamps and along the winding streams of Morrison time there were developed a group of the most remarkable reptiles that the world has ever known. Many of them were swamp-loving creatures of enormous bulk. Some of them were vegetable eaters, which lived on soft vegetation and found safety in the streams and marshes. Others were ferocious killers that preyed on the more peaceful vegetable eaters.
Little is known of the kinds of vegetation that furnished food for these bulky creatures. Few fossil plants have been found in the Morrison formation. But the great size of these enormous reptiles implies an abundant supply of food.
Dinosaur National Monument
Some of the finest specimens of dinosaurs of Morrison time have been found in the plateau country of northeastern Utah. Because of its remarkable deposits of well preserved bones, a small tract of land that includes the best collecting ground has been set aside as the property of the public and called Dinosaur National Monument. This reserve was created in 1915 for the purpose of preserving the fossil bones. The monument embraces 80 acres of land, and its surface rocks are called by some the McElmo formation, although they are equivalent in age to the Morrison. The dinosaur skeletons are among the largest and the best preserved yet found.
Dinosaur bones were found many years ago at Como Bluff and elsewhere in Wyoming, and for a time the rocks in which they occur were called the Como beds. About the same time bones were found at Morrison and other places in Colorado, in rocks that were first called the Atlantosaurus beds but that were later called the Morrison formation. It is now known that the bone beds at all these localities are of the same geologic age, and the name Morrison is usually applied to all of them, but for those in Utah and other places in the Southwest the name McElmo is still used.
Although the Morrison is here described as a formation in the Jurassic system, some geologists believe that it should be included in the Cretaceous system rather than the Jurassic. It is the only representative of the long period between late Jurassic time and the middle part of the Cretaceous period.
Discovery of Dinosaurs in America
The great interest in the dinosaurs may justify an account of their discovery. But what constitutes discovery? If finding bones without recognizing them as such is discovery, the date and place of discovery remain unknown; if seeing large bones and leaving them undisturbed and undescribed constitutes discovery, Major Powell discovered them in 1869 at Flaming Gorge; if viewing certain dinosaur bones without recognizing them as dinosaurs is discovery, Professor Marsh discovered them in 1872 at Como, Wyo.; if unannounced collections constitute discovery, Mr. W. H. Reed must be given the credit. But if prompt public announcement is to be recognized, the credit seems to be equally divided between Mr. O. Lucas and Professor Edward D. Cope on the one hand and Professors Arthur Lakes and O. C. Marsh on the other.
The late Dr. S. W. Williston of Chicago University, who was closely associated with the several claimants and who has told the circumstances, holds that the discovery is to be attributed to "a state of mind." For years, according to him, beds containing great numbers of these bones had been studied by geologists of experience, but scarcely a scrap of bone had been recognized, although acres of surface were literally strewn with fragments. Some of these were so large as to tax the strength of a strong man to lift them. Pieces of dinosaur bone had been collected for years by tourists on the supposition that they were fossil wood. If this constitutes discovery there is no means of knowing when dinosaurs were discovered.
But in 1877 occurred what Professor Williston calls "a state of mind," by which three men, each unknown to the others, were impelled to find out what the fossils meant. W. H. Reed, in tramping over the hills of Wyoming in the winter and spring of 1877, found some fossil bones at Como Bluff and in the following autumn sent them to Professor O. C. Marsh at Yale University. Williston was sent by Marsh to Como Bluff, and in November, 1877, he and Reed opened the quarry from which much material was obtained later. Marsh had seen fragments of these bones at Como Bluff five years earlier but was then engrossed with other matters and paid little attention to them.
Mr. O. Lucas, an amateur botanist, found bones at Garden Park, near Canon City, Colo., in March, 1877. These he sent to Cope at Philadelphia, who described them. Later much material was collected at this locality by Marsh.
Professor Arthur Lakes found a large fossil vertebra near Morrison, Colo., in March, 1877. He sent this to Marsh, who described the fossil as belonging to Titanosaurus (Atlantosaurus) immanis. The beds were therefore long called the Atlantosaurus beds, but they were later named the Morrison formation.
The fossil bones are very abundant in some places, and many museums are well supplied with them. A small tail vertebra which I found in Wyoming years ago while collecting there with Professor Williston is doing service on my desk as a paper weight while I write this account. Carloads of the bones have been unearthed, and several nearly complete skeletons have been restored. The newest and perhaps the richest collecting ground is in Dinosaur National Monument.
In many ways the reptiles of Morrison time were the most singularly interesting creatures that ever lived. Some of them were the largest beings that ever walked on land. Reptiles reached their highest development at this time. They were the rulers on the land, in the water, and in the air. Their bones were preserved in great numbers in western North America, where conditions were especially favorable for their preservation, but some have been found in eastern North America, in Europe, in Africa, and in other parts of the world.
Como Bluff is classic ground to those who are interested in the fossil remains of these animals. In the bluff above the now abandoned station of Aurora W. H. Reed found the large petrified limb bone which Marsh recognized as belonging to some extinct animal then unknown. He enlisted the service of Mr. Reed, who, with others, carried on collecting here for ten years or more, and as a result of this and similar work done elsewhere Marsh was able to publish the restorations of dinosaurs that appeared from time to time in several publications.
The dinosaurs differed greatly in size, shape, structure, and habits. Some were plant eaters, others fed on flesh; some walked on four feet, others, with small, weak forelimbs, walked entirely upon strongly developed hind legs; some had reptile-like feet, others were bird footed; some had toes provided with long, sharp claws, others had flattened hoof-like nails. There were dinosaurs with small heads and dinosaurs with large heads. Some were bulky and cumbersome; others were small, light and graceful and in their structure resembled birds so closely that only the skilled anatomist can distinguish between their remains. Some enormous ones were clad in coats of bony armor, which gave them a bizarre appearance, like the old-time knight-errant or the modern war tank.
A Thunder Lizard
The largest herbivorous or plant-eating dinosaur whose fossil remains have been found in Como Bluff was the huge brontosaurus, or thunder lizard, as it was called by Professor Marsh. It was 70 feet long, stood 15 feet high at the hips, and had a long tail, an equally long neck, and a head that was only a little larger than that of a horse. The weight of such a creature has been variously estimated at 18 to 40 tons. This animal doubtless lived on luxuriant tropical vegetation, but how its enormous bulk could be sustained by such food as could pass through its ridiculously small mouth has caused much wonder. It is not certain whether the name thunder lizard was given to it because of its size, or because of the large summore than $10,000which Professor Marsh spent in excavating it and preparing it for exhibition.
Some dinosaurs that are even larger than the brontosaurus have been found more recently. A diplodocus now in the Carnegie Museum at Pittsburgh had a length of more than 84 feet. Some whose remains have still more recently been dug out in the Dinosaur National Monument are even larger.
At the time these creatures flourished western America was low, nearly level, and probably covered with tropical vegetation. It contained many wide, shallow streams and swampy areas, thus furnishing a congenial place for these sluggish, swamp-inhabiting creatures where they might wade leisurely about or float in the water; for it seems improbable that the enormous bulk of some of them could be sustained without lateral support such as they would obtain in water.
The life of the peaceful plant-eating dinosaur, however, was not always serene, for there lived at the same time dinosaurs whose powerful jaws, armed with long, sharp teeth, indicate that they lived on flesh. These animals are called allosaurs (Plate XXVII, B). That they fed upon large dinosaurs and smaller animals of their kind is indicated by the discovery of teeth of the carnivorous species together with the bones of their herbivorous contemporaries and of a skeleton of one of the herbivorous dinosaurs with bones scarred with the tooth marks and grooves corresponding exactly to the sharp pointed teeth of the allosaurs.
The allosaur was a powerful animal and is represented by skeletons over 20 feet long. The large bones of the limbs were hollow, as were many other parts of the skeleton, this structure facilitating rapid movement. The feet were armed with long, sharp claws, especially the forefeet, which were well adapted for catching and holding prey or for tearing and rending skin and flesh.
How old is it? This is one of the first questions asked when a fossil is exhibited. It is difficult to answer that question, and it is perhaps still more difficult for one who has given little thought to the subject to realize the great lengths of time represented by the geologic ages. The life of an individual is so short compared with the life of a race that great effort is required to realize even the march of human events. Yet the whole range of human history is only a very small fraction of a geologic period. W. D. Matthew, who has spent much time in working out the relative duration of the periods, has shown that if the age of reptiles should be represented by a single line extending across a page, the duration of human history would be represented by a line so short that it would be invisible to our eyes.
I have already referred to the first thunder lizard found by Professor Marsh and of the cost of obtaining the remains of that monster. A still better conception of the difficulties encountered and of the labor required for such work is given by Doctor Matthew in his description of a great skeleton, 66 feet long, of an animal whose weight in life is estimated at 38 tons. This skeleton, now in the American Museum of Natural History, was discovered north of Medicine Bow, Wyo., in 1898. The paleontologists spent the following summer in extracting it from the rock and in shipping it to the museum. Then for nearly two years workmen were busy chipping away the stone, and still more time was consumed in fixing the bones in place. At last, in 1905, after seven years' work, the great brontosaur was ready to receive visitors.
The proper posture of this great animal required much thought, for the dinosaur belongs to a lost race and has left no direct descendants. The fashions followed by this ancient monster and its habits have caused much discussion. It had a long, thick tail like a crocodile, a long, slim neck, a short, stout body, and massive legs like an elephant, only very much larger. The track of one foot covers nearly a square yard. Its bones were massive and heavy and were constructed with an elaborate pattern of braces and buttresses for the attachment of the huge muscles. The head was small, and the teeth indicate a vegetable diet.
After a general summary of the known characters of other lizards, it has been generally agreed that the thunder lizard lived chiefly in water; sometimes in muddy swamps, where he fed on succulent swamp vegetation; sometimes in rivers, where his massive, heavy bones made it possible for him to walk on the bottom under water where he was safe from his enemy, the allosaurus, while the plants on the bank were within easy reach of his long, flexible neck. However, Professor Williston thinks that Mrs. Brontosaurus must have walked out on land sometimes, "because reptile eggs can not hatch in water." Contemplate for a moment a nest of eggs laid by a 38 ton dinosaur!
The thunder lizard had several relatives, some larger and some smaller than himself. Among these may be mentioned diplodocus, a dinosaur that has become well known because of a splendid skeleton now in the Carnegie Museum at Pittsburgh. This skeleton has become famous through presentation of plaster casts of it to museums in foreign countries.
The first skeleton of diplodocus was found near Canon City, Colo., but better material was collected later at the Bone Cabin quarry near Medicine Bow, Wyo., a locality that has become classic to bone hunters because of the great number and variety of fossil bones found there. It was a kind of museum, perhaps better described as a graveyard, of all the reptiles of the period. From this quarry have been taken nearly 100,000 pounds of bones, representing seventy-three animals, and this weight does not include bones rejected as worthless, nor does it include the entire deposit. An unknown number of skeletons still remain in the rocks, and no doubt there are at least as many more as have been taken out.
Those whose interest in natural objects is confined to their commercial value may be interested in the utilization of dinosaur bones near Canon City, Colo., where large quantities of petrified bones have been cut into ornaments. The bones there were petrified by silicious material, producing red, brown and yellow jasper, with gray and white matrix, consisting in part of chalcedony. The replacement of different parts of the bone tissue by minerals of different colors has produced a variety of effects. The structure of the bone is shown well by spots and mottlings of dark jasper in a light-colored matrix. Some of the petrified bone polishes well and makes handsome ornamental stone. The fact that jewels are cut from petrified dinosaur bones is not extensively advertised, and many a man is wearing a watch charm, and many a woman carries a breastpin cut in the latest style from bones of a reptile that long ago went out of fashion.
Certain little gastropods lived at the time the dinosaurs flourished, and their shells, buried in the mud with the bones, have been petrified in carnelian-colored agate. One species of these gastropods was named in my honor. I am not certain just how much I should feel honored by having my name attached to a snail, but I feel some satisfaction in possessing a scarf pin consisting of a shell of Valvata Leei petrified in jewel agate.
Classic literature and the writings of later centuries abound in references to mythical beings that filled the imagination of the ancients. Classic art and the art of later centuries depicted these mythical beings in statuary, in painting, and in decorative architecture. The dinosaurs and other creatures of past ages make an appeal to popular imagination like that of some of the monsters of classic lore. Published pictures and descriptions of them are popular. The reproductions of the reptiles seem well adapted also for use in the field of caricature. When a cast of diplodocus was set up in South Kensington Museum, many amusing cartoons bearing upon the political events of the day appeared in the daily papers of England, in which this reptile was made to do service. It was made also to serve in commercial enterprise, as it was used by both the advertising agent and the modeler. "Diplodocus vases," bearing on their sides figures of the creature in high relief, were placed on the market in London by one of the best known firms engaged in the manufacture of majolica.
One of the largest known dinosaurs lived in Utah. Its bones were dug up in the Dinosaur National Monument and sent to Carnegie Museum, where it was named, in honor of Mrs. Andrew Carnegie, Apatosaurus Louisæ. In addition to being one of the largest creatures that ever walked on earth, its skeleton is said to be the most complete ever recovered of this remarkable race of extinct reptiles. So much of the skeleton was obtained (sixty-four out of the seventy-three vertebrae of the tail and other bones in like proportion) that there is little chance that the place or the natural relation of any of the bones is mistaken.
A Plated Lizard
The discovery of the extraordinary creature called stegosaurus was one of the great achievements of Professor Marsh, but since his day more nearly perfect skeletons have been found and placed on exhibition. The curious aspect of this animal makes it one of the most interesting of museum exhibits. This plated lizard was a vegetarian and was one of the strangest looking creatures of that strange time. The name plated lizard was given to it because of the bony plates on its back (Plate XXVIII, A). Some of these plates, although thin, were two or three feet across. They were held in upright position in parallel rows along the middle part of the back, extending from the base of the skull well down on the tail, the tip of which was armed with two pairs of long, bony spines. In some individuals these spines were over 3 feet in length. During life all the plates and spines were covered by a thick, horny skin.
The stegosaurs were about 20 feet long and stood about 10 feet high at the hips. The head was extremely small and lizard-like, the brain was small, the eyes were large, and the nostrils indicate a considerable power of smell. The great disproportion in length between the fore and hind legs, the small, pointed head, and the plates and spines made it so ugly that it may not have required other means of protection. Some passive protection, through repulsive ugliness or otherwise, seems to have been necessary, for its ludicrously diminutive brain suggests a mental power insufficient for conscious efforts at self-preservation.
Its want of brain capacity was compensated to some extent by an enlargement of its spinal cord near the hips that was about ten times as large as its brain. This curious characteristic inspired Mr. B. L. Taylor of the Chicago Tribune to the following metrical effort:
Behold the mighty dinosaur,
Where Triton and Titan Wrestled
A skeleton of a gigantic creature called allosaurus, 34 feet long and 8 feet high, now in the American Museum of Natural History at New York, was found at Como Bluff in 1879 and sent to Professor Cope. The bones remained boxed for years in Philadelphia until the collection was removed to the museum, where, in 1903, they were unpacked. It was then recognized that a treasure had come to light, for this is the finest specimen of its kind known.
Something of the appearance of this creature may be inferred from Plate XXVIII, A. The leathery skin; the long, powerful hind legs, with toes ending in claws; the small forelimbs, adapted to grasping its prey; the long heavy tail for balancing; and the powerful, heavily toothed jaws, all denote a predatory animal of great ferocity.
There were small flesh eaters as well as large ones. One of these, called Ornitholestes, was found at Bone Cabin quarry, Wyo. It had long hind legs for rapid movement, and short forelimbs with slender fingers adapted for grasping an active prey, such as the primitive birds, which were contemporaneous with it (Plate XXXVIII, B). The bird-catching dinosaur contrasted in many ways with its contemporaries. It was only about 7 feet long and was built on a plan designed for speed and agility. The bones were mere hollow shells, with walls as thin as paper. Its feet and hands were birdlike, the hands especially resembling those of the early birds in the great elongation of the first finger and the abbreviation of the other fingers.
The Sea and the Mountains
During all the time that the thick Jurassic deposits were accumulating in the West and during most of Lower Cretaceous time, the ancestral Rockies in Colorado and neighboring States were undergoing the last stages of destruction. Over the plains thus built up on the west and worn down on the east the sea water advanced in Upper Cretaceous time. At one time or another during this epoch the sea occupied the interior of North America from the Gulf of Mexico to the Arctic Ocean, and from Utah to the Mississippi River.
The country east of this interior sea was low and supplied little sediment, but the country west of it, the mountainous area that had furnished the great volumes of sand and silt during Jurassic and Lower Cretaceous time, seems to have been reelevated and supplied the rock débris that gradually filled the interior basin. The advance of the sea over the plain must have been relatively rapid in a geologic sense, for the subsidence of a nearly level surface, even though very slow, would cause the strand line to move over it rather rapidly. During this advance of the sea, the sand and silt brought to it by streams were sorted by the waves, and the washed sand was deposited on the migrating beach. This sand hardened to form the group of beds which most geologists know as Dakota.
As the sea advanced the beach sand was covered with water, in which accumulated the material that formed the beds of shale, limestone, and sandstone of the Upper Cretaceous series of rocks. In the plateau country these rocks consist chiefly of sandstone. The material was derived from the highlands to the west, and in working eastward, whether carried by currents of the sea or washed over low-lying coastal plains by streams, the sand was deposited first and the fine silt was carried farther toward the east, where the rocks of this age consist of shale that originated as deposits of silt.
As the deposits accumulated the floor of the basin sank, but at no time was the water very deep. The sediments were distributed over the bed of the sea in thin, regular layers, which could have been formed only in shallow water or on low-lying coastal plains. Furthermore, the subsidence was not regular. For long periods the land remained stationary. During such periods the basin was filled near shore and the strand line was pushed far out into the basin.
The low-lying flats thus formed of sand and mud were favorable to the luxuriant growth of plants and to the formation of great swamps. In these swamps accumulated the vegetable matter which was later buried and turned into coal. In this way were formed great layers of sandstone, one of which caps Mesa Verde, in Mesa Verde National Park, and the extensive beds of coal found in the Cretaceous rocks of western America.
Last Updated: 31-Dec-2009