STRUCTURES COMMON TO ALL ROCKS. 231 



mentions a fissure in Pennsyl- 

 vania in which the vertical dis- 

 placement is 20,000 feet, and 

 may be traced for twenty miles. 

 Rogers describes one in southern 

 Virginia in which the displace- 

 ment is 8,000 feet, and may be 

 traced for eighty miles (Fig. 

 136). 



According to Powell, there is 

 on the north side of the Uintah 

 Mountains a vertical slip of 

 20,000 feet. All along the east- 

 ern side of the Sierra there is a 

 slip of not less than 15,000 to 

 20,000 feet ; and King thinks 

 the slip on the west side of the 

 Wahsatch is even 40,000 feet. 

 But they are developed on per- 

 haps the grandest scale in the 

 Colorado plateau region. This 

 high plateau is traversed by a 

 system of north and south fis- 

 sures, 100 to 200 miles long, by 

 which the arched earth-crust is 

 broken into huge blocks, and 

 these have settled to different 

 levels, some 5,000 to 12,000 feet 

 below others, and thus give rise 

 to a wonderful system of north 

 and south cliffs (Fig. 137). 



If such a slip takes place sud- 

 denly, then at first there must 

 have been a cliff as great as the 

 slip. The same would be true 

 even \vith gnidutil slipping, if 



