THE BLACK HILLS AND BAD LANDS.
In order to thoroughly appreciate and enjoy the wonderful caves of South Dakota, which are found within the limits of the Black Hills, it is necessary to have some knowledge of the geological character and history of that peculiar region.
Prof. J. E. Todd, State Geologist, in his "Preliminary Report on the Geology of South Dakota," gives an interesting "Historical Sketch of Explorations" in his state, beginning with the expedition of Captains Lewis and Clark to the upper Missouri regions in 1804-6 to explore that portion of the recent Louisiana Purchase for the government and notify the Indians of the transfer; and including all other important expeditions since that time down to his own official tour of the Black Hills and Bad Lands in 1894. His own descriptions are so concise and graphic as to invite quotation. Of the Hills he says:
"The Black Hills have an area of five-thousand square miles of a rudely elliptical form with its major axis, approximately, north-northwest. Most of this area lies within our state. The true limit of the Hills is quite distinctly marked by a sharp ridge of sandstone, three hundred to six hundred feet in relative height, which becomes broader and more plateau-like towards the north and south ends. This ridge is separated from the higher mass of hills within by a valley one to three miles in breadth, which is known as the Red Valley, from its brick-red soil, or the 'race course,' which name was given it by the Indians because of its open and smooth character, affording easy and rapid passage around the Hills. The junction of the outer base of the Hills with the surrounding table lands has an altitude of three thousand, five hundred to four thousand feet. Within this Red Valley one gradually ascends the outer slope of the Hills and soon enters, at an altitude of four thousand five hundred or five thousand feet, the woody portion of the region. This outer slope varies greatly in width and is underlaid by older sedimentary rocks, cut in almost every direction by narrow deep cañons. This feature covers nearly the whole of the western half of the Hills proper, where erosion has been less active on account of its distance from the main channels of drainage. Usually, from the broken interior edge of this slope or sedimentary plateau one descends a bluff or escarpment, and enters the central area of slates, granite, and quartzites, which is carved into high ridges and sharp peaks cut by many narrow and deep valleys and ravines and generally thickly timbered with the common pine of the Rocky Mountains. Toward the south, about Harney Peak, the surface is peculiarly rugged and difficult to traverse. Toward the north, also, about Terry and Custer peaks, a smaller rugged surface appears; but in the central area between and extending west of the Harney range is a region which is characterized by open and level parks much lower than the surrounding peaks and ridges."
The Archæan rocks which form the core of the Hills mark the center of the various uplifts which have attended their formation and controlled their history. The coarse granite of Harney Peak indicating that, as the central point of the earliest upheaval, and the three porphyries known as rhyolite, trachyte, and phonolite, showing the uplifts of later periods to have had their centers a little more to the north, but the entire area is said to be only about sixty miles long and twenty-five miles in width. It is exceptionally rough and mountainous, and consequently has great charms for the lover of fine scenery. Erosion has only partially denuded the peaks of the sedimentary rocks through which they were thrust up, or by which they were overlaid during the earlier part of several subsequent periods of submersion. The Hills, in these remote times, led but a doubtful and precarious existence, being now an isolated island rising out of a shallow sea, and then, owing to a general subsidence, submerged in the ocean to so great a depth that even Harney Peak is supposed to have almost, if not entirely, disappeared. This up and down motion continued at intervals until the Fox Hills epoch of the Cretaceous Age, at the close of which the sea retired forever from that portion of the country. In the next epoch fresh water work began and extensive marshes were formed, with an abundant growth of vegetation and reptiles. There was also much volcanic violence which resulted in the fine scenery in the north end of the Black Hills, and probably opened the fissures to form Wind Cave, the Onyx Caves in the southern hills and Crystal Cave near the eastern edge toward the north. This was near the close of the Cretaceous Age. But here is a point on which the best authorities who have studied the porphyry peaks, have failed to agree; Prof. N. H. Winchell believing that the intrusion occurred, probably, during the Jura Trias, but as Cretaceous beds, of more recent date, are found to have been distorted by the outflow, it seems that Professors Todd, Newton and Carpenter hold the stronger position and that the later time is correct.
No record of the next geological stage, which was the Eocene, or earlier part of the Tertiary Age, has been found in the Hills, because they were at that time dry land with gently flowing, shallow streams, and consequently no strata were laid down; but they are supposed, through later evidences, to have had a tropical climate and vegetation, enjoyed by large animals of strange new forms. The volume of fresh water afterwards became so great that immense lakes spread over large portions of the west, one of which occupied most of the region around the Black Hills at the beginning of the Miocene, and animal life was more abundant than ever before and of higher orders, many species being the same as are now in existence. The weather became more and more inclement and as the storms increased the erosion of the Hills also increased, and the rivers changed to torrents with deep channels. Earthquakes are supposed to have occurred and also volcanic eruptions.
The Black Hills were now rising steadily, and as the slope of the streams increased, the channels cut deeper, and the fissures now known as caves had long been filled with water.
The most important of the numerous animals of the Tertiary Age yet discovered in the Hills and surrounding region, are the Titanotherium or Brontotherium, similar to our Hippopotamus, the Oreodon, and a small horse having three toes on each foot. A little later in the same Age the horses were similar to those of the present time and of equal size, which proves that the wild horses of the West were not descended from the few lost by the Spanish Invaders. At this time the first lions, camels, mastodons, and mammoths also appeared. The remains of these animals are so abundant in places as to indicate that they perished in herds that were overwhelmed suddenly by great floods, and many, no doubt, huddled together and perished with cold; for with the beginning of the present age the Hills had reached their highest elevation, the inclement weather increased, and the tropical climate suddenly changed to one extremely cold. It was the beginning of the Glacial Period or Ice Age, when a large portion of the United States is supposed to have been covered by a sheet of ice. The ice is believed to have entered South Dakota from the northeast and its drift across the state limited by a line so closely following the present course of the Missouri River that many of us would be inclined to consider it the western bluff. Beyond this line the ice failed to push its way, but the Hills were subject to heavy rain storms that filled the streams and carried large quantities of bowlders and other eroded material, both coarse and fine, down into the valleys and over the lower hills, where much of the moderately coarse can now be seen exposed on the surface, and fine specimens collected without the use of a hammer. The brilliantly colored, striped and mottled agates, and the bright, delicate tints of the quartz crystal, are particularly attractive to the majority of visitors. The beauty of these gaily colored rocks is quite extensively utilized by the inhabitants of the southern and southeastern hills to supply the place of growing plants which are generally denied by the inconvenience of the water supply. The quartzite of the Hills is well crystallized and heavy. I have one beautiful specimen of the dark Indian red variety through which passes a narrow line of pale blue, and the yellow quartzite or jasper sometimes shows dendrite markings. Very great quantities of agates and jasper, mostly in small pieces, but unlimited variety, are to be seen in portions of the Bad Lands, south of the fork of the Cheyenne River, with an almost equal abundance of baculites and numerous other fossils.
The wide expanse of deep ravines and sharp, barren ridges in the Bad Lands is a unique departure from the usual phases of natural scenery that inspire interest and wonder, but no great admiration, until one soon learns that the law of compensation has been strictly observed. The beauty of vegetation denied those desolate buttes and ridges is atoned for by a marvelous abundance of most wonderful crystals of aragonite, calcite, barite and satin spar; each to itself, or two or more combined in beautiful geodes or else arranged in great flat slabs crystallized on both sides of a thin sheet of lime. These slabs are composed of crystals of uniform size and of a pale green tint. But the geodes show some striking combinations of both crystals and colors with an exterior formed like box work, composed of a very heavy dark material said to be a mixture of barium, calcium and iron. The interior may be a bright green or lemon yellow, or perhaps the two in combination, while others yet may be either of these varieties with the addition of flat crystals of almost transparent satin spar. These crystals also occur in masses of the same box-like formation rising just so much above the surface of the barren ridge they occupy as to give it the appearance of a prairie dog town. One hill-top over which an abundance of detached crystals, of the palest water-green tint, has been spread, gave the impression of being covered with crushed ice. This transformation from a richly tropical to a marvelously barren region, was accomplished during the time when storms reigned over the Hills and ice ruled the country to the north and east.
The long slender barite crystals of a bright golden brown color are especially beautiful but are generally seen in the specimen stores, as the deposit is confined to limited areas and the few persons familiar with the locations are not over anxious to introduce the general public.
The fossil remains previously referred to are of course only a few of the most important, but it is remarked as a curious and notable fact that among the fossils of the lower orders of life in the Bad Lands, the heads have not been preserved. On account of scarcity of water it is necessary for parties to carry a supply even when they expect to be in the vicinity of the Cheyenne River and probably ford the South fork, as these waters carry in solution a quantity of alkali that renders them unfit for drinking, although the effects would not be fatal but simply the extreme reverse of pleasant.
No caves have been discovered in the Bad Lands, unless that name be applied to some of the geodes which are really grottoes, they being of sufficient size for a man to stand in. The Black Hills, however, contain some of the most remarkable caves ever yet discovered, of which those of greatest importance are Wind Cave and the three Onyx Caves near Hot Springs, in the southeastern part of the Hills, and Crystal Cave near Piedmont, in the northeast. All of these occur in the Carboniferous Limestone which forms an outer belt around the central mass or core of the Hills and no doubt, as previously suggested, owes its fissures to earthquakes which preceded or accompanied the porphyry intrusions by which in some localities its strata have been thrown into a vertical position.