438 Nezv York State Museum 



Ohio river. Along the Pacific coast through this time 

 were shifting seas of deposition covering narrow strips 

 along the coast of Mexico, California, Washington and 

 Oregon and northward into Alaska. In the western in- 

 terior in the region between the Sierra Nevada s and the 

 Rocky mountains and east of the Rockies in the Great 

 Plains region occur continental sediments deposited partly 

 in alluvial fans, partly in lakes, also in flood plains, in 

 deltas and in swamps. Toward the end of Tertiary time 

 there was a period of widespread elevation (Pliocene). 

 The eastern coast of North America was practically the 

 same as today. North of New York the coast extended 

 farther out than at present and the greater part of Florida 

 was under water. Continental deposits occur in wide 

 areas in the coastal plain region along the Atlantic and 

 Gulf coasts. On the Pacific coast sedimentation changed 

 from marine to fresh-water, and in the western interior 

 continental deposits were widely scattered and of limited 

 extent. 



There were periods of mountain building and igneous 

 activity during the Tertiary. The greatest volcanic ac- 

 tivity since Precambrian times occurred then, particu- 

 larly in the Miocene period. The early Tertiary 

 (Eocene) was brought to a close by crustal movements. 

 Some mountain ranges already in existence were bowed 

 up, and the Coast ranges began their growth. In the 

 later Eocene, elevation and erosion in Oregon and Wash- 

 ington were accompanied by volcanic activity and ex- 

 tensive lava flows. During Middle Tertiary (Miocene) 

 times there was mountain building accompanied by vol- 

 canic activity in Washington, Oregon and Idaho and 

 along the Pacific ranges in California, resulting in great 

 uplift of the Coast ranges of California and Oregon and 



