
CHAP TERS XI 
FAULTS OR DISLOCATIONS 
Normal Faults. Dip-faults and Strike-faults—their effect upon Outcrops. 
Oblique Faults. Systems of Faults. Step-faults. Trough- and 
Ridge-faults. Shifting of Faults. Reversed Faults. Transcurrent 
Faults. Origin of Faults. 
HAVING now learned that rocks of all kinds are more or less 
fissured, and that no small proportion of the joints by which 
they are thus traversed appear to owe their origin to crustal 
movements, we must next make the acquaintance of fissures 
of another kind, known as Faults or Dislocations. These 
are doubtless due likewise to crustal movements, but they 
differ from joints in being not mere cracks or rents, but 
fissures of displacement. The rocks on one side of a fault are 
thus abruptly truncated and brought against younger or older 
rocks on the other side. Three types of faults are recognised, 
namely, Normal Faults (or Downthrows), Reversed Faults 
(or Overthrusts), and Tvranscurrent Faults (or Transverse 
Thrusts). 
NORMAL FAULTS.—These dislocations are rarely, if ever, 
quite vertical, although in natural exposures they sometimes 
appear to be so. But when they are followed downwards, as 
in mining operations, they are invariably found to be 
inclined, the degree of inclination varying, it may be, from 
point to point, so that in places they occasionally show 
verticality. The general inclination of a fault from the 
vertical is termed the hade, and this, in the case of normal 
faults, is always ‘in the direction of the downthrow. The 
degree of deviation from the vertical is quite indeterminate ; 
but, as a general rule, the larger are more steeply inclined 
than the smaller faults. But to this rule many exceptions 
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