384 CUBA AND POKTO HICO 



there may have been a few Paleozoic nucleal rocks in 

 Cuba and Santo Domingo, but even this is uncertain, for 

 the oldest positively determined rocks belong to the 

 Cretaceous, Tertiary, and Pleistocene ages. During these 

 later epochs remarkable changes have taken place in the 

 Antilles, following one another with such rapidity that they 

 have made a more complicated history than all the events 

 that marked the earlier ages of the mainland. 



At the close of the Cretaceous period the Great Antilles 

 were regions of volcanic activity, by which material was 

 transferred from the bosom of the earth into gigantic 

 heaps of volcanic rocks. Whether these stood as islands 

 in the sea or rose from a body of preexisting land no one 

 can answer, but the vast heaps of land-derived gravel 

 and conglomerate which make the great thicknesses of old 

 sedimentary rock in the Antillean Mountains and consti- 

 tute the oldest-known formations of Barbados and the 

 Virgin Islands lead to the conclusion that at the begin- 

 ning of Tertiary time there were land areas in the West 

 Indies concerning the shape and area of which we cannot 

 even speculate. This may have been a still earlier At- 

 lantis than the one we have above suggested. At this time 

 the Caribbean chain was probably a line of active volcanoes. 



Then followed another vast revolution. The preex- 

 isting lands subsided beneath the sea to great depths, in 

 places five miles or more, until only the merest tips of 

 the highest land of the Great Antilles remained above the 

 sea. Then these were probably reduced to small islands, 

 possibly as diminutive as the smallest Caribbee of to-day, 

 and their former areas covered with the calcareous radio- 

 larian slime of the ocean's bottom. This was in the second 

 quarter of the Tertiary history. 



Then came, in the third quarter of Tertiary history, 

 another revolution by which the ocean's floor was cor- 

 rugated into land, and the old sediments with the deep 

 sea chalks and muds were folded into the gigantic Antil- 

 lean mountain systems, which at this time probably 



