438 



HISTORICAL GEOLOGY 



Wyoming the Tertiary strata have preserved abundant leaves of 

 palms, figs, and magnolias. The present dryness is doubtless to 

 be ascribed in part to the later uplifting of the present mountain 

 ranges which shut off the moist winds from the Pacific Ocean. 

 Mountain growth. In the West, the Eocene epoch was 

 occupied largely in the wearing down of the highlands which 

 had been produced at the close of the Cretaceous period, 

 and in the filling of the lowlands. Warping and volcanic 

 activity, although they had not ceased, were of minor im- 

 portance. It was an epoch of quiescence. 



FIG. 455. Trend lines of folds made during the middle Tertiary epoch of 

 mountain-building. 



Near the middle of the Tertiary (Miocene epoch), how- 

 ever, the disturbances were renewed on quite as grand a 

 scale as before, but in part along different lines. One of the 

 greatest results of this deformation is now seen in the series 

 of high mountain chains which partially encircles the globe 

 north of the equator (Fig. 455). In our own hemisphere it 



