DEGRADATION. 



* 



ditions, would seem to attest to rapid rate, but the character of the strain 

 may have determined the rupture. Hence we may conclude that the 

 characteristics of the displacement do not afford satisfactory evidence of the 

 rate of its movement. 



It will be seen hereafter that facts relating to degradation and sedimen- 

 tation do give some satisfactory conclusions. 



DEGRADATION. 

 EXTENT OF DEGRADATION. 



The area of degradation which I have often for convenience called the 

 region of uplift, represented in Plate II, embraces a little more than 2,800 

 square miles. From this about 8,300 cubic miles of rock have been carried 

 away by rains and rivers a mean degradation of about three cubic miles 

 to the square mile But a part of the region embraced on that plate will 

 be discussed hereafter under the head of Yampa Plateau, and in what I 

 have said concerning the Uinta Mountains above, this region has not been 

 considered. Taking the Uinta Mountain region proper, then, we have an area 

 of about 2,000 square miles from which about 7,100 cubic miles of rock have 

 been taken, giving a mean degradation of 3^ cubic miles to every square mile 

 of surface. But this has not been taken from all points equally ; a greater 

 amount has been carried from the axial region than from the districts along 

 the flanks ; and in the axial region a greater amount has been taken from 

 the eastern than from the western end. Here where the displacement lines 

 are carried highest, the surface lines are lowest, so that the degradation is 

 more, not only by the amount of greater uplift but also by an additional 

 amount in the deeper excavation of the valley. The 'region of highest 

 uplift is the region of lowest degradation, and here more than 25,000 feet 

 of beds have been removed. 



To more fully comprehend the amount of degradation and its relation to 

 upheaval, the bird's-eye view, Plate IV, has been constructed. Here we 

 have represented a block from the Uinta Mountains forty miles in a north 

 and south, and fifty miles in an east and west, direction. The one-half of 

 the view in the foreground represents the degraded region, and the one -half 



