526 GEOTECTONIC (STRUCTURAL) GEOLOGY. [Boox IV. — 
Connection between Faults and Folds.—A monoclinal fold may 
by increase of movement be developed into a fault (Fig. 255). 
Beautiful examples of this relation have been observed by Powell 
and others among the little disturbed formations of the great 
plateaux of Utah and Wyoming. Other illustrations have been 
adduced by Heim from the more plicated rocks of the Alps.’ 

Fic. 255.—Sxrcrions TO SHOW THE RELATIONS OF MonocLINAL Fonps AND FAULTS. 
1, Monoclinal fold; 2, Monoclinal fold replaced by a single fracture ; 3, Monoclinal 
fold converted into a series of parallel fractures; 4, Monoclinal fold developed by 
increase of plication into a reversed fault. 
Throw of Faults.—That faults are vertical displacements of 
parts of the earth’s crust is most clearly shown when they traverse 
stratified rocks, for the regular lines of bedding and the originally 
flat position of these rocks afford a measure of the disturbance. In 
Fig. 254 the same series of strata occur, on either side of each of the 
two faults, and the same stratum can be recognized, so that measure- 
ment of the amount of displacement is here obviously simple. The 
measurement is made from the truncated end of any given stratum 
vertically to the level of the opposite end of the same stratum on 
the other side of the fault. Where the fault is vertical, like that to 
the right in Fig. 254, the mere distance of the fractured ends from each 
other is the amount.of displacement. In an inclined fault the level 
of the selected stratum is protracted across the fissure until a 
vertical from it will reach the level of the same bed, as shown by the 
dotted lines. The length of this vertical is the amount of vertical 
displacement, or the throw of the fault. 
Unless beds the horizons of which are known can be recognized on 
both sides of a fault, exposed in a cliff or other section, the fault at that 
particular place does not reveal the extent of its displacement. It 
would not, in such a case, be safe to pronounce the fault to be large 
or small in the amount of its throw, unless we had other evidence 
from which to infer the geological horizon of the beds on either side. 
A fault with a considerable amount of displacement may make little 
show ina cliff, while, on the other hand, one which, to judge from the _ 
jumbled and fractured ends of the beds on either side, might be 
supposed to be a powerful dislocation, may be found to be of com- 
eetyely slight importance. ‘Thus, on the cliff near Stonehaven, in 
incardineshire, one of the most notable faults in Great Britain runs 
out to sea, between the ancient crystalline rocks of the Highlands 
' See Powell in the works cited already on p. 516. Heim, Mechanismus der Gebirgs- 
bildung, Plate xv., Fig. 14. 

