10 



FOSSIL FORESTS OF YELLOWSTONE PAEK. 



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. 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. If the beds had been tilted at a considerable angle, 

 these trunks could project from the surface for only a short distance 

 before their weight would break them off, showing again the re- 

 markably stable conditions that have continued since the trunks were 

 covered up. 



AMETHYST MOUNTAIN. 



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. In the 

 steeper middle portion of the mountain face, rows of upright trunks stand 

 out on the ledges like the columns of a ruined temple. On the more gentle 

 slopes farther down, but where it is still too steep to support vegetation, save 

 a few pines, the petrified trunks fairly cover the surface, and were at first 

 supposed by us to be shattered remains of a recent forest.* 



These trunks may easily be seen from the road along the Lamar 

 River, about a mile aw^ay. They stand upright — as Holmes has said, 

 like the pillars cf some ruined temple — and a closer view shows that 

 there is a succession of these forests, one above another. In the 

 foothills and several hundred feet above the valley there is a per- 

 pendicular wall of volcanic breccia, w-hich in some places attains a 

 height of nearly 100 feet. 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, wdiich are 2 to 4 feet 

 in diameter and 20 to 4.0 feet high, are so far weathered out of the 

 rock 'as to appear just ready to fall; others are only slightly ex- 

 posed ; niches mark the places from which others have already fallen ; 

 and the foot of the cliff is piled high with fragments of various sizes. 



1 Holmes, W. H., Twelfth Ann. Kept. V. S. Geol. and Geogr. Surv. Terr., 1878 (1883), 

 p. 48. 



