156 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
poured out a lava flow, hh' , which flowed against the clifl^ base. (3) 
A third faulting movement, dropping the region west of the fault to 
its present position, but leaving a thin strip of the later lava adhering 
to the face of the clift'. 
It appears from the foregoing that this part of the Hurricane Cliffs 
is directly due to the second and third comparatively recent faulting 
movements, and that the erosion which followed the first faulting re- 
duced the region to a peneplain which was covered by the older lava 
flow. This lava flow prevented the differential erosion which gave 
fault-line cliffs along some of the other faults, and along other portions 
of this same fault. The cliffs in the Virgin River portion of the Hurri- 
FiG. E. — East-west section through Hurricane Fault, soutli of Virgin River, showing 
relation of beds to Sugar Loaf Mesa (farther south), with evidence of three 
periods of faulting. 
cane Ledge are then true fault clitt's of much more recent date than the 
fault-line clift's we have considered under preceding headings. 
If we take into account the monoclinal folding of the plateau series 
which preceded the first faulting, and ignore the "drag" of the down- 
thrown beds which is strongly developed in the Virgin River section, 
the succession of events in the geological history of the Hurricane Ledge 
region of which we are cognizant may be represented by the accom- 
panying rough diagrams (fig. F-INI; not drawn to scale). 
Since the last faulting there has been sufficient erosion to remove 
part of the lava strip from the face of the cliff in places, to develop 
erosion channels in the surface of the flow at the base of the cliffs, 
and to allow the gorges which open in the face of the cliffs partially to 
grade their courses, although cascades may be found in the lower, 
