1922] 



EDWARDS, GEOLOGICAL WORK AT GRAND CANYON 



103 



county funds. In ascending this trail, one crosses in the reverse order, 

 all the rocks passed over on the Hermit Trail. It is a much more direct 

 route than the Hermit Trail in spite of the many zigzags which it makes. 

 Bright Angel Trail is made possible by the existence of a fault which 

 has raised the rocks on the west side about one hundred and twenty- 

 five feet higher than those on its east side. In this way the two re- 

 sistant formations, the Coconino sandstone and the Redwall limestone 

 have been broken and the debris along the fault makes possible a path 

 across these two formations. As one climbs upward, he comes at one 



Fig. 59. — The wall of Coconino sandstone, west of Bright Angel Trail, 



Grand Canyon. 



point face to face with the vertical cliffs of the Coconino sandstone 

 and is able to see, as in figure 59, the cross-bedding which characterizes 

 this formation, and which is probably due to the action of wind or 

 waves at the time when the sandstone was a loose and drifting mass of 

 sand. At the lower edge of the cliff, a very sharp contact with the 

 underlying red rocks can be plainly made out. At the point where the 

 trail crosses the fault, there is a small tunnel leading through a mass 

 of the Coconino sandstone and cutting off a shoulder of rock. Above 

 this tunnel the trail zigzags back and forth, as shown in figure 60, 



