TJ. S. GEOLOGICAL SURVEY 



BULLETIN 707 PLATE XI 



A. CASTLE ROCK. 



A well-known landmark about 300 feet high, 33 miles south of Denver. It was first noted and 

 named by the Long expedition in 1820. The cap rock, 60 or 70 feet thick, is made up of 

 boulders of various sizes cemented together (conglomerate) and stands out prominently 

 because it is harder than the underlying rock. Photograph by L. C. McClure, Denver. 



B. DOME ROCK, PLATTE CANYON. 



This picture illustrates the manner in which even the most massive granite may yield to the 

 action of the weather. It peels off in successive curved layers much like the layers of an 

 onion, leaving round or dome-shaped masses of rock which stand out in striking contrast to 

 the towers and pinnacles that generally occur on the walls of the canyon. Photograph by 

 L. C. McClure, Denver; furnished by the Colorado & Southern Railway. 



