124 GUIDEBOOK OF THE WESTERN UNITED STATES. 
stream.' Every rain fills the side canyons with rushing torrents, 
which carry into the river a heavy load of débris washed from the 
adjoining slopes. It has been by this means that the canyon was 
excavated, and the deepening and widening process is still in active 
operation. It began at the surface of the plateau and it will continue 
until the river reaches a grade so low that it can no longer move the 
débris; meanwhile the side streams will cut away the adjoining slopes 
and the canyon will widen until its sides become gentle slopes. 
Under present conditions this will require a million years or more. 
The formations exposed in the walls of the Grand Canyon are the 
rocks which underlie the Arizona Plateau, and most of 
them extend far beyond that province. The first 3,600 
feet of beds, all of which lie nearly horizontal, are as follows: 
Rocks. 
Strata above granite, in walls of Grand Canyon (beginning at brink of the canyon). 
Feet. 
Limestone, light colored, partly cherty, mostly massive (Kaibab). 700 
Sandstone, light gray, massive, cross-bedded (Coconino) 300 
/ 
Sandstones and shales, all red (Supai forma MON istyoue tS 1, 100 
imestone, light blue-gray, massive, surface mostly stained red 
“ce pga, ne SSS ae eee eae 550 
Shale, with limestone and sandstone layers. ... 800 
Sandstone, hard, dirty gray to buff (on granite) \Tonto sis dee { 150 
These formations are readily recognized by their color or character, 
as they are practically uniform in aspect and relative position from 
all points of view. (See Pl. XXXII, p. 126.) The top limestone, 
which caps the great plateaus on both sides of the canyon, has been 
removed in whole or in part from some of the promontories and 
buttes that project into the canyon; the Coconino, Supai, or Redwall 
ads have been removed from the lower-lying features. The out- 
cropping edge of the Coconino sandstone? is marked by a distinct 
band of light-gray rock all along the canyon walls 700 to 800 feet 
below the top. The red beds of the Supai formation® everywhere 
————— 
‘A very large amount of material is | and Angels Gate, as well as Buddha, 
removed from the land and carried to the Zoroaster, Brahma, Deva, and Vishnu 
oceans by all rivers. Careful estimates temples and other similar features on 
based on analyses of river waters and which more or less of the overlying lime- 
measurements of volume of flow have | stone remains . 
shown that in a year the rivers of the * Such features as O’ Neill Butte, New- 
United States carry to tidewater 513,000,- | ton Butte, Tower of Set, Tower of Ra, 
000 tons of sediment in suspension and | Horus Temple, hrine, Lyell 
270,000,000 tons of dissolved matter Butte, and Sagittarius Ridge consist of 
of 783,000,000 tons represents Su ormation is con- 
more than 350,000,000 cubic yards of | spicuous in the slopes of many great 
rocks, or a cube of about two-fifths of a ridges capped by higher beds, such as 
2 This sands tone also caps many buttes Temple, Osiris Temple, Zoroaster Tem- 
such as Isis, Osiris, and Manu temples, | ple, and Vishnu Temple. ps 
aa at ast “ S 2 i i 7 
a. 
