56 GRAND CANON DISTRICT. 



Wasatch Mountain range, being wholly disconnected from it and stand- 

 ing with a wide interval en Schelon to the southeast ward of it. The Wa- 

 satch Plateau presents a long, straight, horizontal summit projected 

 against the sky without peaks or domes, resembling somewhat the ridges 



of Pennsylvania and Virginia, but on a grander scale. We perceive 

 along its entire western front a rapid slope, descending to the bottom of 

 the San Pete Valley at its foot. It is not deeply incised with ravines 

 and amphitheaters, nor notched with profound transverse gorges, as arc 

 ordinary mountain ranges, but shows a slightly diversified slope in every 

 part. As we draw nearer we begin to sec the attitudes of the strata 

 composing its mass, or, as the geologists say, its " structure." The strata 

 are inclined at the same angle as the slope of its flank. In the valley 

 below, the beds are horizontal ; as they approach the base of the plateau 

 they flex upwards and ascend the slope ; as they reach the summit they 

 flex back to horizontally. If we ascend the plateau and ride eastward 

 a very few miles, there suddenly breaks upon the view a vast and im- 

 pressive panorama. From an altitude of more than 11,000 feel the eye 

 can sweep a semicircle with a radius of more than 70 miles, and reach far 

 out into the heart of the Plateau country. We stand upon strata of Lower 

 Tertiary age, and beneath our feet is a precipice leaping down across the 

 level edges ofthe beds upon a terrace 1,200 feet below. The cliff on which 

 we stand stretches far northward into the hazy distance, gradually swing- 

 ing eastward and then southward through acourse of more than a hundred 

 miles, and vanishing below the horizon. It describes, as we well know, 

 a rude semicircle, around a center about 40 miles east of our standpoint. 

 At the foot of this cliff is a terrace of greatly varying width, rarely less 

 than 5 miles, consisting of Upper Cretaceous beds nearly but not quite 

 horizontal. They incline upwards towards the east at angles rarely so 

 great as 3°, and are soon cut off by a second cliff plunging down 1,800 

 feet upon Middle Cretaceous beds. This second cliff describes a semi- 

 circle like the first, but smaller and concentric with it. From its foot 

 the strata still rise gently towards the east, through a distance of about 

 10 miles, and are cut off as before by a third series of cliffs concentric with 

 the first and second. For the fourth and fifth time this process is re- 

 peated. In the center of these girdling walls is an elliptical area about 

 40 miles long and 12 to 20 miles broad, completely surrounded by mural 

 escarpments more than a thousand feet high.' This central spot is 

 called the San Rafael Swell, and it is full of interest and suggestion 

 to the geologist. From its central point the strata dip away in all 

 directions, the inclinations, however, being always very small.* This 

 configuration of the strata (dipping away from a central point in all 

 directions) is technically termed "quaquaversal." 



The accompanying diagram (Plate XI) shows the relative masses and 

 positions ot the strata as they woukUippear in vertical sections cutting 



JfhT 1 ! 10 e T rU mUrgin ° f tbe 8wdl ^i^flh^e^^t^ monoclinallle^uTes 7 ' 

 * 7 J , mcl,nati0u 80 characteristic of tbe Plateau Country. These will be ad- 

 verted to berealter. 



