A region of great popular and scientific interest in the Yellowstone Park, although as yet hardly known to the tourist, owing to the incomplete condition of the road system, is that of the Fossil Forests in the north-east corner of the Park. The facts which have been brought to light concerning the origin of these forests are worthy of particular consideration.
The trees are found to occur in different planes or horizons of growth, one above another, until the whole series represents a thickness of many hundreds, and possibly thousands, of feet. Going back to the first of these growths, it is found to have been destroyed by an outpouring of volcanic material, which partially or wholly submerged it. After the flow had ceased, the ordinary atmospheric and aqueous agencies began work, eroding the surface in some places and depositing the products of erosion in others, while vegetation rapidly covered the newly-formed soil. A subsequent flow destroyed this second growth and gave a new horizon, on which the same process was repeated. This continued until there were at least nine, and probably twelve, of these consecutive growths.
Terry Engr. Co.
U. S. Geological Survey of the Territories.
Section of Amethyst Mountains.
The lava flows in this particular section do not seem to have been characterized by great heat. They were composed of volcanic agglomerate, in which there was a large admixture of mud and water, with sufficient heat to destroy life, but not to char or consume its products. The percolation of siliceous waters gradually turned the arboreal vegetation into stone by the process of substitution, and thus preserved in these silent monuments a record of the events which once transpired there. When the last of the eruptions had ceased, there existed in this locality a vast depth of volcanic ejectamenta, composed of many layers, on each of which was standing, buried in the layer next above, the trunks of extinct forest growths.
Terry Engr. Co.