THE APPALACHIAN REVOLUTION 439 



From the distribution of the animals and plants of the southern 

 Permian, it is altogether probable that there was land communi- 

 cation between India, southern Africa, and South America, and less 

 directly with Australia. 



Close of the Permian 



One of the greatest revolutions in the history of the North Amer- 

 ican continent culminated at the end of the Permian, though it 

 probably began in the Carboniferous. With the exception of the 

 mountain making at the close of the Ordovician, the Palaeozoic era 

 in North America had been a time of slow, even development, with 

 many oscillations of level, but without violent disturbances, and with 

 singularly few manifestations of volcanic activity. A little more 

 land was added to the northern area during each period, but, so 

 far as we can trace it, the geography of the Ordovician does not 

 seem to have been very different from that of the Carboniferous. 

 Throughout this long era, doubtless more than equal to all subse- 

 quent time, the Appalachian geosyncline had been sinking, though 

 with many shifts and oscillations, under an ever-increasing load of 

 sediment, until the great trough contained a thickness of 30,000 to 

 40,000 feet of strata. Eventually the trough began to yield to 

 the lateral compression exerted by the shrinking crust, and its 

 contained strata were thrown into folds, or fractured by great 

 overthrust faults. Thus, in place of a sinking sea-bottom along 

 the shore of the great Interior Sea, rose the Appalachian Moun- 

 tains, which in their youth may have been a very lofty range, 

 rivalling the Alps in height. This range extends from the Hudson 

 River to Alabama ; another range from Newfoundland to Rhode 

 Island, and a third, the Ouachita Mountains of Arkansas, are 

 attributed to the same set of disturbances, which thus made them- 

 selves felt for a distance of 2000 miles. In the West the results 

 of this revolution are much less clearly shown. Either at the close 

 of the Carboniferous or of the Permian, the Great Basin region, of 

 western Utah and eastern Nevada, was upheaved into land, and at 

 the present time the surface rocks over most of this region are 



