NEW EROSION CYCLE IN GRAND CANYON DISTRICT 743 



appreciated, thus indicating the recent nature of the growth of 

 physiography from the descriptive to the broader interpretative 

 stage. 



REVIEW OF FORMER WORK 



It will assist in understanding the bearing of this new cycle 

 of erosion on the Tertiary history of the region if a partial summary 

 of some of the former work is first presented. The actual amount 

 is, indeed, not great, considering the length of time the region has 

 been known and its interest recognized; possibly the extent of 

 the field and the evident inaccessibility of much of it have exer- 

 cised a deterrent influence. 



The nature of the plateau problem was clearly appreciated by 

 Newberry who in 1858 was the second geologist to traverse the 

 region. His route lead him along the southern side of the Grand 

 Canyon, and the conclusion he reached from the character of that 

 and other parts of the plateau was that erosion had been the pre- 

 dominant factor in producing the relief. The following quotation 

 will give his point of view: 



.... Before returning to the details of the local geology of our route, I 

 ought perhaps to refer briefly to two questions of general importance, which 

 would naturally suggest themselves to any geologist who should traverse the 

 table-lands west of the Rocky Mountains, or should receive an accurate descrip- 

 tion of them from others. 



The first of these questions is: To what cause is due the peculiar topographic 

 features of the surface of the table-lands — where different formations succeed 

 each other in a series of steps, which generally present abrupt and wall-like 

 edges — the more recent strata occupying the highest portion of the plateau ? 



The first question belongs appropriately to the subject of surface geology, 

 and will be referred to again. I may say here, however, that, like the great 

 canyons of the Colorado, the broad vaUeys bounded by high and perpendicular 

 walls belong to a vast system of erosion, and are wholly due to the action of water. 

 Probably nowhere in the world has the action of this agent produced results so 

 surprising, both as regards their magnitude and their peculiar character.^ 



The first extended account of the region, however, did not 

 appear until 1882 when Button's Tertiary History of the Grand 

 Canyon District was published. The history of the region as 



I Report on the Colorado River of the West. Explored in 1857-1858, hy Lieut. J. C. 

 Ives. Washington, 1861. Part III, Geological Report by J. S. Newberry, p. 45. 



