GEOGRAPHICAL DEVELOPMENT OF THE AMERICAS 125 



it must have been submerged in the Miocene, otherwise there 

 would not have been the open pathway for the Cetacea of 

 Patagonia to reach the Atlantic coast of North America and 

 vice versa. 



5. Pliocene Epoch 



North America. — The Pliocene of North America is not 

 nearly so well displayed or so satisfactorily known as the pre- 

 ceding Tertiary epochs, and only of comparatively late years 

 has it been recognized at all upon the Atlantic coast. The 

 Atlantic and Gulf shores had very nearly their present outlines, 

 but with some notable differences. It would seem that the 

 northeastern portion of the continent stood at a higher level 

 than it does now, north Greenland being joined with the islands 

 of the Arctic archipelago and Newfoundland with Labrador, 

 the Gulf of St. Lawrence then being land. From Nova Scotia 

 to southern New Jersey the coast-Une was many miles to the 

 east and south of its present position, but the sea encroached 

 here and there upon the shores of Virginia, the Carolinas and 

 Georgia, and southern Florida was mostly under water, as was 

 also a narrow strip of the Gulf coast from Florida to Texas 

 and along the east of Mexico. On the Pacific side of the con- 

 tinent the marine Pliocene is far thicker and more important 

 than on the east coast and in California is largely made up of 

 volcanic materials. Quite extensive disturbances in this 

 region had marked the close of the Miocene, the strata of which 

 in the Goast Range had been violently compressed and folded. 

 An elevation of the land had caused the sea to withdraw from 

 the central valley of California and had restored Lower CaU- 

 fornia to its peninsular conditions, reducing the gulf to the 

 narrow Umits which it had had in the lower Miocene and ex- 

 tending southern Mexico to the west and south. British 

 Columbia and southeastern Alaska stood at higher than their 

 present levels and the countless islands of that region were 

 part of the mainland. Bering Strait was closed, for at least 

 a great part of the epoch, and, as a continuous shore-line was 



