20 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
has no fellow on the west side of the gulch where the slope consists 
wholiy of tuff. Some of the tuff stands up in little ridges bordering the 
base of the ash cone and seems to have a steep dip to the west. The 
vertical displacement here indicated by the lava bed may be one hundred 
feet or more. A northward continuation of this subrecent movement is 
suggested by a low west-facing lava scarp that may be traced for a mile 
or more north of Vulcan’s throne on the eastern side of Toroweap valley 
floor. A still more recent movement is indicated by a small but distinct 
scarp, about twenty feet in height, that traverses a gravel wash on the 
east side of the south Toroweap valley, somewhat east of the main fault 
line. This scarp was seen in a sunset view from Vulcan’s throne, when 
in spite of its distance of about three miles, the low western sunshine 
WES ES FAN AD = 
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REDWALL 
Ficure 7. 
Sketch section at Vulean’s Throne. 
brought it distinctly to sight. A significant amount of faulting must 
therefore be recognized as having occurred near the canyon at least, 
after the esplanade had been formed and after lavas had been poured on 
its floor. On the other hand, there seems to be no sufficient reason for 
regarding the chief movement on the Toroweap fault, amounting to six 
hundred or seven hundred feet according to Dutton, as having occurred 
in the canyon cycle. Analogy with the neighboring great faults would 
suggest an earlier origin in the plateau cycle; this opinion is not at all 
contradicted by the dislocation of the esplanade, and it is supported by 
the considerable width attained by the Toroweap valleys, north and 
south of the canyon, as explained in my earlier article (b, p. 143, 184). 
The decrease of the displacement northward along the valley reported 
by Dutton (b, p. 93) is probably more apparent than real; the heavy lava 
flows on the valley floor would tend to conceal the escarpments by which 
the fault is so clearly revealed at the canyon. 
