Plate XX 



An area southwest of Denver, showing a mountain ridge dissected by 

 erosion. The mountain range appears as a series of long hills in line These 

 loni; hills are the outcropping edge of a tilted layer of hard rock. The breaks 

 in the ridge are the results of erosion. Ridges of this sort are often called 

 "hogbacks." Scale about 2 miles per inch. Contour interval, 50 ft. 

 (Denver, Colo., Sheet, U. S. Geol. Surv.) 



