588 THE MIOCENE PERIOD 



place earlier (p. 583). The Cascade Mountains of Washington were 

 in process of growth at this time. 1 



Similar movements were widespread east of the coast, as in the 

 Great Basin region and elsewhere. In some places, they deformed 

 strata heretofore horizontal, but more commonly they affected 

 formations and areas which had suffered deformation earlier. 



The later part of the period was perhaps the time when the 

 greater relief features of the rugged west, as they now exist, were 



Fig. 494. Courthouse and Jail Rocks. Buttes of the Arikaree (Miocene) 

 formation of western Nebraska. (Darton, U. S. Geol. Surv.) 



initiated. The great relief features of earlier times appear to have 

 lost their greatness before this time. After the movements of the 

 late Miocene had been accomplished, it is probable that the western 

 part of the continent had a topography comparable, in its relief, to 

 that of the present, though by no means in close correspondence with 

 it. The details, and many of the larger features, of the present 

 topography are of still later origin. 



In the eastern part of the continent, the geographic changes 

 were less, though the Atlantic and Gulf regions seem to have 

 emerged, shifting the coast-line to some such position as it has 

 today. 



Foreign 



Europe. As compared with the Eocene, the sea on this conti- 

 nent was somewhat restricted in the north, and somewhat extended 

 1 Willis, Professional Paper 19, U. S. Geol. Surv. 



