HUNTINGTON AND GOLDTHWAIT: THE HURRICANE FAULT. 249 
recent faulting. Accordingly Davis (4, p. 148) infers that the Grand 
Wash fault, like the Hurricane, is double, one part being old, the other 
new. Nothing that we saw contradicts this so far as the southern part 
of the displacement is concerned close to the Colorado river. In the 
northern part of the Grand wash, however, we saw evidence of only one 
displacement, and that was of recent date. Apparently the old fault 
was of small dimensions compared to the modern one, and died out some 
fifteen or twenty miles farther south. 
Taking up once more the recent displacement as a whole, we find that 
at Kanarra, the northern limit of our study, it is a true fault with a 
throw of two thousand feet or more. This decreases toward the south, 
very slowly at first, but later quite rapidly, until at Toquerville it passes 
into a monoclinal fold by which the lava sheet of Toquer hill is bent 
steeply upward some eight hundred feet. In the neighborhood of this 
hill the displacement is complicated by a number of small fractures, and 
is set off about three miles to the east in en echelon fashion. The 
amount of displacement continues to decrease until at the point where 
the Virgin river crosses the fault it amounts to only three hundred 
feet. Here, it will be remembered, lay the axis of the gentle anticline 
of the inter-fault cycle. Farther south the displacement again in- 
creases for ten or fifteen miles until it amounts to fifteen hundred feet. 
It then decreases, and south of Fort Pierce almost wholly disappears 
along the line of the Hurricane. This does not mean, however, that 
the displacement is lost. It merely turns from a north and south course 
and goes southwestward. Instead of being a sharp fault it takes the 
form of a long gently sloping monocline which descends toward the 
northwest. The northern limit of this slope lies a few miles south of 
the Virgin river ; its southern limit extends from south of Fort Pierce to 
Black Rock. At the latter point the line of displacement again turns 
south, at first merely as a syncline and then as a true fault, the throw of 
which increases until at the Colorado river it is over five thousand feet. 
Black Rock is a central point, on every side of which there was uplift. 
To the south and east the strata were uplifted smoothly and form part 
of the upheaved plateau block. On the other sides they were uplifted 
in the form of a very flat cone one-third of which is replaced by the 
horizontal strata. It is as though most of the plateau block had been 
cut apart from the St. George block, but this one part remained attached, 
and when the eastern block was lifted up it pulled a corner of the west- 
ern block up with it. The deep cutting of the Virgin canyon where 
that river passes through the Virgin mountains a dozen miles north of 
