Chapter IV Cliffs and Terraces
There is a great group of table-lands constituting a geographic unit which have been named the Terrace Plateaus. They ex-tend from the Paria and Colorado on the east to the Grand Wash and Pine Mountains on the west, and they are bounded on the south by the Grand Canyon of the Colorado, and on the north they divide the waters of the Colorado from the waters of the Sevier, which flows northward and then westward until it is lost in the sands of the Great Desert. It is an irregular system of great plateaus with subordinate mesas and buttes separated by lines of cliffs and dissected by canyons.
In this region all of the features which have been described as found in other portions of the province are grouped except only the cliffs of volcanic ashes, the volcanic cones, and the volcanic domes. The volcanic mountains, cinder cones, and coulees, the majestic plateaus and elaborate mesas, the sculptured buttes and canyon gorges, are all found here, but on a more stupendous scale. The volcanic mountains are higher, the cinder cones are larger, the coulees are more extensive and are often sheets of naked, black rock, the plateaus are more lofty, the cliffs are on a grander scale, the canyons are of profounder depth; and the Grand Canyon of the Colorado, the most stupendous gorge known on the globe, with a great river surging through it, bounds it on the south.
The east-and-west cliffs are escarpments of degradation, the north-and-south cliffs are, in the main, though not always, escarpments of displacement. Let us understand what this means. Over the entire region limestones, shales, and sandstones were deposited through long periods of geologic time to the thickness of many thousands of feet; then the country was upheaved and tilted toward the north; but the Colorado
River was flowing when the tilting commenced, and the upheaval was very slow, so that the river cleared away the obstruction to its channel as fast as it was presented, and this is the Grand Canyon. The rocks above were carried away by rains and rivers, but not evenly all over the country; nor by washing out valleys and leaving hills, but by carving the country into terraces. The upper and later-formed rocks are found far to the north, their edges standing in cliffs; then still earlier rocks are found rising to the southward, until they terminate in cliffs; and then a third series rises to the southward and ends in cliffs, and finally a fourth series, the oldest rocks, terminating in the Grand Canyon wall, which is a line of cliffs. There are in a general way four great lines of cliffs extending from east to west across the district and presenting their faces, or escarpments, southward. If these cliffs are climbed it is found that each plateau or terrace dips gently to the northward until it meets with another line of cliffs, which must be ascended to reach the summit of another plateau. Place a book before you on a table with its front edge toward you, rest another book on the back of this, place a third on the back of the second, and in like manner a fourth on the third. Now the leaves of the books dip from you and the cut edges stand in tiny escarpments facing you. So the rock-formed leaves of
A GROUP OF STONE CORRALS.
CLIFFS AND TERRACES.
these books of geology have the escarpment edges turned southward, while each book itself dips northward, and the crest of each plateau book is the summit of a line of cliffs. These cliffs of erosion have been described as running from east to west, but they diverge from that course in many ways. First, canyons run from north to south through them, and where these canyons are found deep angles occur; then sharp salients extend from the cliffs on the backs of the lower plateaus. Each great escarpment is made up more or less of minor terraces, or steps; and at the foot of each grand escarpment there is always a great talus, or sloping pile of rocks, and many marvelous buttes stand in front of the cliffs.
But these east-and-west cliffs and the plateaus which they form are divided by north-and-south lines in another manner. The country has been faulted along north-and-south lines or planes. These faults are breaks in the strata varying from 1,000 or 2,000 to 4,000 or 5,000 feet in verticality. On the very eastern margin the rocks are dropped down several thousand feet, or, which means the same thing, the rocks are upheaved on the west side; that is, the beds that were originally horizontal have been differentially displaced, so that on the west side of the fracture the strata are several thousand feet higher than they are on the east side of the fracture. The line of displacement is known as the Echo Cliff Fault. West of this about twenty-five miles, there is another fault with its throw to the east, the upheaved rocks being on the west. This fault varies from 1,500 to 2,500 feet in throw, and extends far to the northward. It is known as the East Kaibab Fault. Still going westward, another fault is found, known as the West Kaibab Fault. Here the throw is on the west side,—that is, the rocks are dropped down to the westward from 1,000 to 2,000 feet. This fault gradually becomes less to the northward and is flexed toward the east until it joins with the East Kaibab Fault. The block between the two faults is the Kaibab Plateau. Going westward from 60 to 70 miles, still another fault is found, known as the Hurricane Ledge Fault. The throw is again on the west side of the fracture and the rocks fall down some thousands of feet. This fault extends far northward into central Utah. To the west 25 or 30 miles is found a fault with the throw still on the west. It has a drop of several thousand feet and extends across the Rio Colorado far to
CANYONS OF THE COLORADO.
the southwest, probably beyond the Arizona-New Mexico line. It also extends far to the north, until it is buried and lost under the Pine Valley Mountains, which are of volcanic origin.
Now let us see what all this means. In order clearly to understand this explanation the reader is referred to the illustration designated “Section and Bird’s-Eye View of the Plateaus North of the Grand Canyon.” Starting at the Grand Wash on the west, the Grand Wash Cliffs, formed by the Grand Wash Fault, are scaled; and if we are but a few miles north of the Grand Canyon we are on the Shiwits Plateau. Its western boundary is the Grand Wash Cliffs, its southern boundary is the Grand Canyon, and its northern boundary is a line of cliffs of degradation, which will be described hereafter. Going eastward across the Shiwits Plateau the Hurricane Cliffs are reached, and climbing them we are on the Uinkaret Plateau, which is bounded on the south by the Grand Canyon and on the north by the Vermilion Cliffs, that rise above its northern foot. Still going eastward 30 or 40 miles to the brink of the Kanab Canyon, the West Kanab Plateau is crossed, which is bounded by the Toroweap Fault on the west, separating it from the Uinkaret Plateau, and by the Kanab Canyon on the east, with the Grand Canyon on the south and the Vermilion Cliffs on the north. Crossing the Kanab, we are on the East Kanab Plateau, which extends about 30 miles to the foot of the West Kaibab Cliffs, or the escarpment of the West Kaibab Fault. This canyon also has the Grand Canyon on the south and the Vermilion Cliffs on the north. Climbing the West Kaibab Fault, we are on the Kaibab Plateau. Now we have been climbing from west to east, and each ascent has been made at a line of cliffs. Crossing the Kaibab Plateau to the East Kaibab Cliffs; the country falls down once more to the top of Marble Canyon Plateau. Crossing this plateau to the eastward, we at last reach the Echo Cliff Fault, where the rocks fall down on the eastern side once more; but the surface of the country itself does not fall down—the later rocks still remain, and the general level of the country is preserved except in one feature of singular interest and beauty, to describe which a little further explanation is necessary.
I have spoken of these north-and-south faults as if they were fractures; and usually they are fractures, but in some places they are flex-
PINK CLIFFS, PAUNSAGUNT PLATEAU.
CLIFFS AND TEEEACES.
ures. The Echo Cliffs displacement is a flexure. Just over the zone of flexure a long ridge extends from north to south, known as the Echo Cliffs. It is composed of a comparatively hard and homogeneous sandstone of a later age than the limestones of the Marble Canyon Plateau west of it; but the flexure dips down so as to carry this sandstone which forms the face of the cliff (presented westward) far under the surface, so that on the east side rocks of still later age are found, the drop being several thousand feet. The inclined red sandstone stands in a ridge more than 75 miles in length, with an escarped face presented to the west and a face of inclined rock to the east. The western side is carved into beautiful alcoves and is buttressed with a magnificent talus, and the red sandstone stands in fractured columns of giant size and marvelous beauty. On the east side the declining beds are carved into pockets, which often hold water. This is the region of the Thousand Wells. The foot of the cliffs on the east side is several hundred feet above the foot of the cliffs on the west side. On the west there is a vast limestone stretch, the top of the Marble Canyon Plateau; on the east there are drifting sand-dunes.
The terraced land described has three sets of terraces: one set on the east, great steps to the Kaibab Plateau; another set on the west, from the Great Basin region to the Kaibab Plateau; and a third set from the Grand Canyon northward. There are thus three sets of cliffs: cliffs facing the east, cliffs facing the west, and cliffs facing the south. The north-and-south cliffs are made by faults; the east-and-west cliffs are made by differential degradation.
The stupendous cliffs by which the plateaus are bounded are of indescribable grandeur and beauty. The cliffs bounding the Kaibab Plateau descend on either side, and this is the culminating portion of the region. All the other plateaus are terraces, with cliffs ascending on the one side and descending on the other. Some of the tables carry dead volcanoes on their backs that are towering mountains, and all of them are dissected by canyons that are gorges of profound depth. But every one of these plateaus has characteristics peculiar to itself and is worthy of its own chapter. On the north there is a pair of plateaus, twins in age, but very distinct in development, the Paunsagunt and Markagunt. They are separated by the Sevier River, which flows northward. Their