Popular Science Monthly/Volume 49/August 1896/The Stone Forest of Florissant
|THE STONE FOREST OF FLORISSANT.|
TO the many who annually wander forth in quest of a "change of scene," and have not yet fully exhausted the wonders of Nature in their search after the purely beautiful, any locality that offers material for special wonderment comes with pleasing interest. One such, which is less generally known than other localities of a somewhat similar character in the United States—indeed, is hardly known beyond the pale of a limited coterie of geologists—is the region of ranch and meadow land which lies within a mile and a half of the line of the Colorado Midland Railroad near to the station of Florissant. In reaching it we have crossed the front or outer range of the Rocky Mountains, traversed
the charming flower gardens of Summit Park at an elevation of nearly nine thousand feet, and have again descended to eight thousand one hundred feet. A gently undulating plain of meadow-land is in the main occupied by Costello's and Halthusen's ranches, and around and about sweep up the chain of heights which help to make up the great backbone of the North American continent. There is little to suggest in this landscape that we are in the heart of the Rockies; the rugged crags to which the mind has affectionately attached itself from childhood's study are hidden beneath a dense covering of piny woodland, or else wander off much in the manner of the Eastern Appalachians. Here and there in the not very distant horizon a peak looms up with special prominence, and occasional patches of snow indicate that the mountain crests lie well above the thirteen thousand and fourteen thousand foot line, for below that line, and generally even above it, the lingering winter snows rapidly depart before the summer's heat. The two thousand feet advantage that we possess in the elevation of this region over that of Mount Washington is in no way indicated by the thermometer; an almost subtropical sunshine warms up the open expanse of the Rocky Mountain parks, and with it there are but few reminders of the chilly blasts that habitually sweep over the crests of the White Hills.
Florissant has long been famous with geologists for the wealth of insect remains which its rocks harbor. No other locality of the earth's surface, not even the famous Oeningen beds of Switzerland, has disclosed an insect fauna of equal variety and abundance, or with characters so well preserved as they are here. From butterfly to beetle, wasp, dragon-fly, and ant, almost every type of this great group of animals belonging to the period of the making of the Florissant rock is represented in the soft and thinly bedded shales which here and there force themselves through the not over-luxuriant covering of sward. If, perhaps, the better specimens have by this time been culled by the ever-grasping geological collector, many yet remain, and with rapture the eye follows the marks of hair and exquisite venation which have withstood a time action of perhaps one hundred thousand to two hundred thousand years.
My own purpose in visiting the Florissant Basin during the past summer was less for the study of its extinct animal remains than for inspecting the débris of the wonderful forest which ages ago had undergone its transmutation into stone, and now reads its own history from monuments which are destined to live for equal ages in the future. With me were a number of students, of both sexes, who had determined to share the pleasures and discomforts of camp travel, from canon to mountain peak, and to whom the quasi-luxuriance of the big Rocky Mountain coach was in no way an obstacle. A few hours' easy journey across the Hayden Divide brought us from our quarters at Green Mountain Falls, on the northern shoulder of Pike's Peak, to the land of ancient lake and dead volcano, where, under the kindly guidance of the ranchero and his amiable daughter, we were almost immediately put in sympathetic touch with the relics of departed life.
To the geological mind the Florissant Basin is an ancient silted lake, the waters of which succumbed to that sure infiltration of sediment which marks the beginning and end of nearly all standing bodies of continental waters. In this case, however, it was not the deposition of sediment within the lake by inflowing streams that produced the lake's annihilation, but in the main the aërial discharges of volcanoes. Even to-day the practiced eye will soon pick out from among the many mountain forms that surround this ranchland the conical contours of the volcano. A few such stand by themselves, neither of great height nor of imposing mass; others are disposed in linear series, much like the cones which so abundantly scatter themselves over the southwestern and Mexican plateaus. We ascended one of these, a conelet of perhaps one hundred and fifty feet elevation, whose partially wooded sides were yet the ancient slag and cinders, and from whose top projected the plug of lava which marked the position of the former vent. In a pit near by could be seen the hard
basalt-trachyte which forms the existing core of the mountain—the material which in early Miocene times, or perhaps still earlier, was active in the distribution of the loose rock fragments which everywhere lie scattered about. In the days of its activity the foot of the volcano bordered a still more ancient lake, or was even immersed in it, as the lacustrine deposits which largely encircle it plainly show. In these are found in scattered spots a number of fresh-water types of mollusks—Planorbis, Physa, Limnea, Valvata, Cyclas—their shells as beautifully preserved as the much more delicate parts of the insects which were shortly added to them.
The eruption came, and with it clouds of ash sailed upward, only to fall back into the lake waters, and with them form a sticky and lasting paste, ultimately to harden into a compact rock. This is to-day the floor of the basin, and in it are wrapped the thousands of insects which at the time disported in the subtropical sunshine, and whose lives were involved in the catastrophe.
Fish remains are still occasionally met with, but they do not appear to be in any way abundant. The heated waters flooded portions of the adjacent dry land, and destroyed the stately forest that grew down to the banks—the forest of giant redwoods (Sequoia) which already then clothed this portion of the North American continent, and whose extension is to be found in the forest heaps of Patoot and Atanekerdlook on the western coast of Greenland, almost under the seventieth parallel of north latitude. It was a different climate then. The Sequoias do not, perhaps, teach us much, since they, or a closely allied species, are still a part of the vegetative product of California, and are to-day a wonder in their own land; but when they reared their majestic trunks above the plains of Florissant, they did so in association with palms and with other representatives of the southern climes. They fell together, and together have their remains been preserved.
The silicified trees of the Florissant Basin are a marked curiosity of the United States. They are less known than the "stone forest" of Arizona, or than the similar mausoleum of the Yellowstone region, but it is only because they have not yet been brought to the attention of the tourist. The trees are at the present time represented only by their stumps. In wandering over the green meadow the eye here and there rests upon a seemingly "bald" spot. Over it are scattered white and yellow chips, and, for anything that the eye can itself distinguish, these could easily be the chips left in the path of work of a recently passing woodsman. The deception is absolute, and it belongs to the stump as well. The knots and gnarls and annular rings are perfectly preserved; the bark stands in prominent relief both by ruggedness and color, and all this not in wood, but in the monumental substance of stone. The precise manner in which the substitution of silica for wood was effected can not now be learned, but, in a general way, we know it to have been brought about as the result of a slow infiltration into the tree trunks of heated waters containing silica in solution.
The remains are fairly numerous, but what strikes one with special astonishment is the giant size which some of them attain. Diameters of six, seven, and eight feet are by no means uncommon, The Giant Stomp. About fifteen feet elevation. and we measured three specimens which spanned ten feet or more. In most instances the stumps hardly rise above the surface, coming up flush with it; therefore, without excavation, it is impossible to say at what height above the roots the measurements were taken. In what might be termed the "king of the forest"—the tree represented in the accompanying illustrations—a definite basis for measurement is presented, inasmuch as the tree has been laid bare to its roots. The stump stands about fifteen feet
high, and at that distance above the roots it measures forty-five feet in girth—a colossus that would hardly be shamed by its more gigantic brethren of the existing redwood forests of California. This, so far as I have been able to ascertain, is the facile princeps of stone foresters—a curiosity in Nature of which the world offers but few duplicates. Imbedded hard within the trunk, and held by it fast as in a vise, are the blades of two gang saws, the wreck of a barbaric effort to section the tree and remove it in parts to the World's Columbian Exposition. It is stated that this effort at desecration was only abandoned after it had involved the expenditure of some three thousand to four thousand dollars.
Near by is a stump whose surface measures eleven feet in diameter, and it may well be that excavation nearer to the roots would disclose a size fully equal to that of its more "costly" neighbor. All in all, the trees in this region are much larger than those of the "petrified forest" of Arizona, and their comparative antiquity gives them a special claim upon the attention of the geologist. In the more southerly tract they rarely attain a diameter of four or at most five feet, and more generally two and three feet give the full measure. Most of the fragments lie prostrate—an indication that there was a subversion of the forest before petrifaction set in, and it is difficult to find pieces of more than four feet continuous length. The trees, so far as botanical study has determined them, were pines, and not the more stately Sequoias of the north. And yet, even with such forms, a giant stature was not exactly absent, for only a short time back a prostrate shattered trunk was measured over a length of about a hundred and fifty feet. It is, by way of contrast, a little remarkable that at Florissant so many (perhaps most) of the trees still retain an upright position, a condition that suggests peaceful decay, or at least one that was not associated with any cataclysm of the land surface. In whatever way overwhelmed to death—and the falling ash would itself be quite competent to effect this—it seems not unlikely that silicification proceeded to a level prescribed by the surface of the heated waters of the lake, above which the trees fell. It would be a satisfaction, certainly, to have excavations conducted here; but whether carried out or not, the region is one that stands with its own interest, and to which the tourist can safely be recommended to carry his explorations in search of Nature's wonderland.