10 



THREE GEOLOGICAL PROVINCES. 



II. SIMPLE ANTICLINAL STRUCTURE. 



Mountains or short ranges carved from simple anticlinals are sometimes 

 found, though this type of structure is not a prevailing one. Usually in 

 such a case the great mountain mass lies in the central zone of the uplift. 

 The fold is, of course, always found truncated by erosion, and the moun- 

 tains represent but the difference between the amount of upheaval and the 

 amount of such erosion. When not complicated by other types of structure 

 the strata dip on all sides from the center of upheaval, gently or more 

 abruptly, but the sides of the folds are never closely appressed. Such 

 mountains in primary form are gently rounded in general outline, modified 

 by the erosion of the streams running down their sides. Sometimes such 



FIG. 1. Section through Junction Mountain, north and south. 



FIG. 2. Section through Junction Mountain, east and west. 



B. P., Brown's Park ; 8. C., Sulphur Creek ; J. T., Jura Trias; U. A., Upper Aubrey ; L. A., Lower 



Aubrey ; R. W., Red Wall ; U., Uinta. 







mountains are severed by rivers running longitudinally, transversely or 

 obliquely through them ; the rivers themselves having their sources in 

 regions far away and passing through the mountains in their courses to the 

 sea. In Northeastern Colorado a short distance above the junction of the 

 Snake River with the Yampa, stands Junction Mountain, which serves as a 



