184 
THE GRAND CA^ON DISTRICT. 
to each other may be conceived by recalling the image of the crescent 
moon. The outer curve or “limb” might answer to the form of the West 
Kaibab fault; the inner curve or “terminator” to the form of the East 
Kaibab flexure; the included horn to the form of the northern portion of the 
plateau. But the southern portion has no such analogy. 
For many miles south of the Paria these dislocations preserve great 
simplicity of character, but as they approach the Colorado River they 
undergo changes and gradually die out. The West Kaibab fault is the first 
to resolve. For about 40 miles it is a simple fault, gradually increasing in 
the amount of its shear from 500 to about 1,800 feet. At this point the 
thrown platform of the Kanab Plateau on the west begins to rise quite 
notably, and slowly brings up the edges of the thrown strata towards the 
level of the Kaibab summit, thus diminishing the fault. About ten miles 
further on a new parallel fault begins, throwing also to the west, and the 
total shear is distiibuted between the original fault and its neighbor. 
Further on a third parallel fault appears, and the displacement is dis- 
tributed among the three, which thus form a series of “step-faults” Mean- 
time, the Kanab platform has been rapidly rising southwardly, while the 
Kaibab has increased its altitude only a very little; and that abrupt escai’p- 
ment which separated the northern part of the Kaibab from the Kanab has 
gradually faded out. But it has not wholly vanished, though it has become 
profoundly modified. In the north a great wall, more than a thousand feet 
high, separates the two; further southward the wall diminishes in height; 
at length the single wall becomes two steps; further on it becomes three 
steps, the heights of which continually decrease; and at last it becomes an 
inclined plane, sloping about 1^° to 2° towards the west, and all the faults 
have vanished or have been replaced by new dislocations trivial in amount. 
The East Kaibab displacement undergoes another set of modifications. 
For more than thirty miles south of Paria it is a simple and abrupt mono 
dine. Near the head of House Rock Valley the monocline divides into 
two steps. This is common enough in faults, but that the same sort 
of phenomenon should be presented by a simple monoclinal flexure is 
very significant and adds another illustration of the complete homology 
between faults and monoclines. The duplex character of the displacement 
