Their Story 



Sentinel Rocks and 



They relate chapters of tremendous 

 earth movements in the past 



Mushroom pillars 

 of sandstone capped 

 with an iron-stone 

 which has protected 

 them from more 

 extensive erosion 



THE western portion of the United 

 States is full of strange rock forms — 

 lofty natural towers, pinnacles and 

 monuments, many of commanding dimen- 

 sions. Some of the rock towers are 

 composed of relatively soft material, such 

 as sandstone, and their history has been one 

 of rapid erosion and disintegration; others 

 of granite stand seemingly unchangeable, 

 yet their very forms show that they too 

 have been the playthings of the elements. 



The light-colored sandstone mushroom- 

 like pillars which are numerous in the 

 vicinity of Monument Park, Colorado, are 

 the visible remnants of a great bed of such 

 sandstone, which in a past geologic age 

 covered this portion of the United States. 

 At intervals through this bed of sandstone 

 there were thin strata or layers of a harder 

 iron-stone, fragments of which are now seen 

 as cappings of the sandstone pillars, pro- 

 tecting them to a considerable degree from 

 erosion. The altitude of these sandstone 

 rocks is about five thousand feet above sea- 

 level, yet they were the ocean's bottom. 



At another point, near the Garden of the 

 Gods, Colorado Springs, the rock towers are 

 of a somewhat harder sandstone. The 

 Major Domo, as it is called, is one of the 

 most striking of the sentinel rocks of this 

 strange garden. It is of red sandstone, and 

 one of the remnants of a great bed of 

 stratified sedimentary rock which, in the 



upheaval of the Rocky Mountains, was 

 actually turned on edge. The "grain" of 

 the rock, therefore, now runs vertically 

 whereas originally it lay flat. 



The leaning pinnacle surmounting one of 

 the ridges of the West Elk Mountains, in 

 Colorado, is a rock of great strength and 

 resistance to erosion. 



. The ridge consists of rock which was loog 

 ago forced up from the bowels of the earth, 

 hot and liquid, and intruded into the layers 

 of sandstone and other sedimentary rocks 

 nearer the surface in a mass several thou- 

 sands of feet thick. It then gradually 

 cooled, consolidated and partially crystal- 

 lized into hard rock. Later, erosion strip- 

 ped off the sedimentary rocks and carved 

 the hard rock into one of the West Elk 

 Mountains, on which may be seen untold 

 numbers of such pinnacles. 



The big Bad Lands of South Dakota 

 constitute a large area of very soft clayey 

 sandstone which was once the bed of a great 

 inland sea. It is now a well elevated 

 region and the elements have cut and 

 carved the rock into every conceivable 

 shape. There are human and animal faces 

 and forms, and towers and ruined castles 

 and palaces, a perfect riot of possible and 

 impossible shapes. The disintegration is in 

 comparatively rapid progress and the soft 

 rock is continually scaling and falling away 

 from the columns and pinnacles. 



K'7(\ 



