CHAPTER IT. 



GEOGRAPHY OF THE GRAND CANON DISTRICT. 



The Grand Canon District— the region draining into the Grand and 

 Marble Canons— is the westernmost division of the Plateau Province. 

 Nearly four-fifths of its area are situated in Northern Arizona. The 

 remaining fifth is situated in Southern Utah. Let us turn our attention 

 for a moment to the portion situated in Utah. It consists of a series of 

 terraces quite similar to those which we have already seen descending 

 from the summit of the Wasatch Plateau to the San Rafael Swell like a 

 colossal stairway. At the top of the stairs are the broad and lofty plat- 

 forms of the High Plateaus of Utah ; at the bottom is the inner expanse 

 of the Grand Cafion District, The summits of the High Plateaus are 

 beds of Lower Eocene age. Descending southward we cross, step by 

 step, the terminal edges of the entire Mesozoic system and the Permian, 

 and when we reach the inner floor of the Grand Canon District we find 

 that it consists of the summit beds of the Carboniferous series patched 

 here and there with lading remnants of the Permian. 



Par beyond the remotest limits of vision stretches the great expanse 

 of Upper Carboniferous beds, flecked with Permian outliers, and rising 

 or falling to form the broader inequalities of level in the surface of the 

 region. The terraces of Southern Utah are the border land between the 

 Hi<di Plateaus on the north and the Carboniferous platform of the Grand 

 Canon on the south, and may be regarded as the appanage of either 

 district. Their nature and meaning may become clearer by glancing a 

 moment at the District of the High Plateaus. 



Let us conceive a right-angled triangle in which the acutest angle is 

 regarded as the apex and the shortest side as the base. Place the apex 

 about 25 miles east of Mount Nebo, the great mountain which marks 

 the southern end of the true Wasatch Range; place the right angle 170 

 or 180 miles due south of the apex, and the other acute angle about 100 

 to 110 miles due west of the right angle. This figure would include 

 pretty nearly all of the summit areas of the High Plateaus. Consider 

 now the north-and-south side reaching from the apex to the right angle. 

 It runs along the crest lines and terraces which look down eastwardly 

 upon the San Rafael district and upon other enormously eroded districts 

 further south. The base reaching westward from the right angle to the 

 other acute angle runs among the terraces which descend from the 

 southern termini of the High Plateaus to the Grand Canon District, 

 The hypothenusc looks northwestward over a portion of the Basin Pro- 

 vince. The High Plateaus themselves are large remnants of Mesozoic 



