128 GUIDEBOOK OF THE WESTERN UNITED STATES. . 
the Hermit trail is very interesting. The descent down the trails 
to the river is especially helpful in affording a sense of the scale 
of the canyon and giving opportunity to inspect the rocks at close 
range. There is neither difficulty nor danger in the journey. The 
Bright Angel trail descends at El Tovar by a great series of zigzags 
following the course of a very old Indian footpath. For the first 700 
feet it goes down the irregular ledges of Kaibab limestone, the base 
of which is reached at the entrance to a small tunnel through which 
the trail passes. At this place there is a fault by which the rocks to 
the west are lifted 125 feet higher than they are to the east. The 
plane of this fault is at the entrance to the tunnel. The relations 
are shown in figure 29. | 
The character of this massive cross-bedded rock is well shown in 
the cliff just west of the fault. Next below are red shales and red 
- sandstones of the Supai formation, 1,100 feet thick, extending to the 
top of a cliff of Redwall limestone, 550 feet thick, down which the 
trail winds in a tortuous course. Thence the trail goes down slopes 
of shale of the Tonto group to the Indian Gardens, where a spring has 
made an oasis formerly utilized by Indians. Not far beyond is the 
platform or broad terrace caused by the basal sandstone of the Tonto 
group making a wide shelf through which the main gorge is cut 1,000 _ 
feet deep into the granite. (See Pl. XXXIII.) On the north side 
of the river is a great mass of dark sandstone, red shale, and limestone 
of the Unkar group, oveflain by shale of the Tonto group farther 
back. These Unkar rocks are twisted and faulted but in general dip 
to the north at a moderate angle, as shown in figure 30 (p. 130). 
From Hopi and Yavapai points, which are within 2 miles of the 
hotels, there are superb views up and down the river, showing a great © 
succession of cliffs, promontories, and buttes in endless variety of form, 
with geologic relations most clearly exhibited. They are all shown 
on sheet 194 (p.130). The crosssections in figure 30 show the general 
bonate now represented by the Kaibab 
limestone. The numerous shells in this 
deposit are those of animals that lived in 
the sea. The water probably was mod- 
erately deep, and it is believed that the 
limy sediments accumulated very slowly 
* 
durinealon 
L=J 
' The time required for the accumulation 
of 700 feet of sediments of this sort must 
have been very great, surely several mil- 
lion years; it continued for a large part if 
not entirely through the later portion of 
the Carboniferous period. 
Upon the Kaibab limestone, which con- 
stitutes the present surface of the high 
plateau, there were deposited many thou- 
beyond the Kaibab Plateau. 
sand feet of sandstones and other rocks 
through Permian, Mesozoic, and Cenozoic 
time. ese rocks originally covered the 
present plateau area but were in greater 
part removed by erosion before the begin- 
ning of the excavation of the canyon. 
Remnants of them may be seen in Red 
Butte, not far south of El Tovar; in 
Cedar Mountain, far to the east on the 
Coconino Plateau; and in the great line 
of the Vermilion Cliffs, far to the north, 
Their re- 
required several million years, 
and most of it was completed before the 
excavation of the present canyon was 
begun, 
