,>UTrox J THE HURRICANE FAULT, ]25 



descend the Queantoweap a few miles, and taming about we sec the effects 



of the fault so plainly that a ehild eould hardly mistake them. Right in 

 the bottom of the valley is the lower braneh with a displacement of about 

 1 ,300 feet. (Plate XXVIII). On the cliff to the right is a second smaller 

 displacement of about 350 feet. Still farther to the right is a third of 

 about 700 feet. Beyond the limits of the diagram is a fourth of about 

 500 feet. Twenty-five miles north of the Colorado the branches have 

 disappeared and a single fault remains, with a shear of about 1,800 feet, 

 and this amount continues nearly constant to the northward for a few 

 miles. At length the fault rapidly increases. Seventy-five miles north of 

 the river, and at the point where the Virgen River crosses it, the throw has 

 become colossal. We stand upon the brink of the cliff with our feet upon 

 the summit of the Carboniferous, and within musket range, 1,500 feet 

 below, is the Jurassic white sandstone. Most of the Jurassic (S00 feel ), 

 the whole of the Trias, which here has unusual thickness (2,800 or 2,900 

 feet), and the whole of the Permian and Permo-Carboniferous (1,200 or 

 1,300 feet), overlie the continuation of the strata on which we stand. 

 The total throw is not far from 0,500 feet. Still northward extends the 

 fault, and still it rapidly increases. At length it reaches a maximum 

 displacement of more than 12,000 feet on the west side of the Markagunt. 

 Continuing northward it gradually decreases, and finally disappears near 

 the western flank of the Tushar Mountains. The entire length of this 

 fault is more than 200 miles. It is throughout its whole extent a primary 

 geological and topographical feature of the region it traverses. 



^Vitli regard to the age of the fault we have some information. It is 

 not probable that all its portions were sheared simultaneously, and it is 

 quite certain that its development was very slow and gradual and pro- 

 gressed through a long stretch of geological time. Confining our atten- 

 tion to that portion extending along the western flank of the Uinkaret, 

 we find that nearly the whole displacement took place after t lie eruption 

 of the oldest basalts, for the fault dislocates the most ancient lava beds. 

 Whether some small portion of it may or may not have existed before 

 these eruptions we cannot positively say, but no evidence of such priority 

 has been noted. On the other hand, all the younger lavas, and some, at 

 least, of the middle-aged lavas flowed across the fault and have not since 

 been cut by it. But some of the middle-aged lavas appear to have suf- 

 fered some dislocation. Hence we infer (1), That the age of this part of 

 the Hurricane fault is not older than the beginning of the Pliocene. (2), 

 That the displacement went on in harmony and conjunction with the vol- 

 canic; activity. (3), That for a long period, historically speaking, it has 

 been quiescent, and no movement has within the historic epoch taken 

 place. (4), That the beginning of the Hurricane fault is older than the 

 beginning of the Toroweap fault. These conclusions are of great impor- 

 tance in unraveling the history of the Grand Canon district, for they at 

 once become links in a chain of reasoning which, though complex, is 

 very systematic and self-consistent. The faults are evidences of vertical 



