620 



REPORT OF NATIONAL MUSEUM, i90i. 



Plains, east of the Sierra Nevada, and south of the North Platte, Sho- 

 shone, and Sweetwater rivers into what he designated as geological 

 provinces — the Park Province, the Plateau Province, and the Basin 

 Province. 



'The first named he described as characterized by broad, massive 

 ranges, sometimes distinct and sometimes coalescing, so as to include 

 the great parks. The mountains comprise high, lofty, snow-clad 

 peaks which form perennial reservoirs for the multitude of streams 

 discharging in part into the Colorado River and thence into the 



Gulf of California, and 

 in part into the Rio 

 Grande and thence 

 into the Gulf of Mex- 



ico. 



The Plateau Prov- 

 ince he described as 

 characterized by many 

 tables bounded b} 7 can- 

 yon and cliff escarp- 

 ments, and on which 

 stand lone mountains 

 and irregular groups 

 of mountains and short 

 ranges. This region 

 drains almost wholl} T 

 into the Colorado 

 River. 



The Basin Province 

 was characterized by 

 short north-and-south 

 mountain ranges and 

 ridges separated by 

 desert valleys, and with a drainage which is almost wholly into the 

 interior salt lakes and sinks. 



Devoting himself mainly to the Uintas, he showed that the} T owed 

 their present configuration to the degradation of a great upheaved 

 block having its axis in an east-and-west direction. This upheaval, 

 which he thought took place very slowl} r and gradually, began at the 

 close of Mesozoic time and continued with slight intermissions until 

 late Cenozoic. The total amount of upheaval in the axial region was 

 more than 30,000 feet. Contemporaneously with upheaval the forces 

 of degradation were at work, though not at the same rate of progress, 

 along the axial line of uplift, the degradation amounting to more than 

 25,000 feet (4f miles), and the mean degradation to 3£ miles; so that 

 over the entire area of about 2,000 square miles some 7,100 cubic 

 miles of rock material have been removed. 



Fig. 117. — Showing- area surveyed and mapped by the Powell sur- 

 vey in 1875-SO. 



