Frank Hall Knowlton

“ As one views these Arizona forests from a little distance, with their hundreds, even thousands, of segments of logs, it is difficult to realize that they are really turned to stone and are now exhumed from the earth. ”

“ As the material in which the fossil forests are now entombed consist of ashes, mud flows, breccia, and the like, not all the beds are of the same texture end hardness, so that erosion has acted unevenly on 10 them and has produced many peculiar rock forms. The grotesque so-called “hoodoos” have been carved out in this manner. The fossil trunks, being usually harder than the surrounding matrix in which they are embedded, have more firmly resisted erosion and now project to different heights above the general level. ”

“ The fossil forests are reached over a road from the Mammoth Hot Springs, or from Camp Roosevelt near Tower Falls, and they are in their way quite as wonderful and worthy of attention as many of the other features for which the Yellowstone National Park is so justly celebrated. ”

“ Enormous amphitheaters have been carved out of the loose agglomerates, and peaks, pinnacles, and relics of great table-lands testify in some measure to the forces of erosion. The plateau is scored by a complete network of deep valleys and gorges, which dissect it in every direction, and lay bare the structure of the vast volcanic pile. [1]
Within the park there is evidence of similar volcanic activity, and it is clear that the basin between the encircling ranges was filled to its present elevation by volcanic flows, which formed the present park plateau. ”

“ The appearance they present (see fig. 1) is not unlike a “log drive” that has been stranded by the receding waters and left until the bark had disappeared and many logs had fallen into partial decay. Trunks of many sizes and lengths are now mingled and scattered about in the wildest profusion, and the surface of the ground is carpeted with fragments of wood that have been splintered and broken from them. ”

“ The fossil forest that was first brought to scientific attention is on the northern slope of Amethyst Mountain, opposite the mouth of Soda Butte Creek, 12 miles southeast of Camp Roosevelt. The following account, by Dr. William H. Holmes, the discoverer of these fossil forests, shows the impression first made by them:
As we ride up the trail that meanders the smooth river bottom [Lamar River] we have but to turn our attention to the cliffs on the right hand to discover a multitude of the bleached trunks of the ancient forests. ”

“ The pieces of wood become more numerous and fresher in appearance upstream toward the bluffs, until at the foot of the cliffs in some places there are hundreds, perhaps thousands of tons that have but recently fallen from the walls above. One traversing the valley of the Lamar River may see at many places numerous upright fossil trunks in the faces of nearly vertical walls. These trunks are not all at a particular level but occur at irregular heights: in fact a section cut down through these 2,000 feet of beds would disclose a succession of fossil forests (see fig. 4) . ”

“ The fossil trunks may be seen in this wall in many places, all of them standing upright, in the position in which they grew. Some of these trunks, which are 2 to 4 feet in diameter and 20 to 40 feet high, are so far weathered out of the rock as to appear just ready to fall: others are only slightly exposed: niches mark the places from which others have already fallen: and the foot of the cliff is piled high with fragments of various sizes. ”

“ As the traveler approaches the forest he will observe a number of trunks standing upright among the stumps and trunks of living trees, and so much resembling them that a near view is necessary to convince him that they are really fossil trunks. Only two rise to a considerable height above the surface. ”

“ In exposed beds that are nearly or quite horizontal, disintegration has acted at nearly equal pace on the trunks and on the matrix, so that the trunks are nearly or quite on a level with the surrounding surface. On steep hillsides, however, from which all loose material is easily and quickly removed, some of the fossil trunks stand up to a height of 20 or 30 feet. ”

“ The living redwood is usually 10 to 15 feet in diameter and ranges in height from 200 to 310 feet, and as the two are so very closely related there is no reason to suppose that the fossil trunk was of less height, but by a moderate estimate it may be accredited with a minimum height of 200 feet. ”

“ There are also two species of fir, the white fir (Abies grandis) and the Balsam fir (Abies lasiocarpa) , and a single juniper (Juniperus communis siberica) , which is often scarcely more than a shrub.
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The deciduous-leaved trees are almost a negligible element in the present park flora, being confined to an occasional cottonwood (Populus angustifolia) at the lower elevations, along the Yellowstone River, and small groves of the quaking aspen (Populus tremuloides) . ”

“ Above this cliff fossil trunks appear in great numbers and in regular succession. As they are all perfectly silicified, they are more resistant than the surrounding matrix and consequently stand above it. Most of them are only a few inches above the surface, but occasionally one rises as high as 5 or 6 feet. The largest trunk observed in the park is found in this locality. It is a little over 10 feet in diameter, a measurement that includes a part of the bark. ”

“ The unit of the measure of the time is the time taken by each forest to grow. Pine trees of the types represented in the fossil trunks require 200 or 300 years to reach maturity, and redwoods may require from 500 to 1,000 years. ”

“ The height attained by the trees of this fossil forest can not be ascertained with certainty, since the tallest trunk now standing is only about 30 feet high, but every one observed is obviously broken off, and does not show even the presence of limbs. ”

“ If there is sufficient moisture and all conditions are favorable this vigorous growth of wood cells may continue without interruption until the approach of cold or dry weather, but not infrequently there may be a brief shortage of moisture, and this is reflected in the formation of a few rows of thicker-walled cells. Such a condition may be observed in the present specimen, in which a slight, partial ring may be seen at some distance above the main ring.
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Fig. 12.—Thin section of wood of fossil redwood (Sequoia magnifica) , showing growth ring. Section transverse. Magnified 100 diameters. ”

“ The section is cut through one of the growth rings, which consists of 12 or 15 rows of very thick-walled cells. The large, regular thin-walled cells, which begin abruptly above the growth ring, belong to the spring wood—that is, the wood first formed after growth starts in spring, when the supply of nourishment is abundant. ”

“ It is found on the higher part of the ridge, and covers several acres. The trees are exposed at various heights on the very steep hillsides, and one remarkable feature of the forest is that most of them project well above the surface. ”

“ The entire mass is made up almost exclusively of Tertiary igneous rocks. * * * Degradation of the mass has taken place on a grand scale. Vast quantities of volcanic ejectmenta have been removed from the summit, but no reliable data exist by which the amount can be estimated even approximately. All the higher portions have been sculptured by glacial ice. ”