CONTINENTAL FOUNDERING 201 



to about the close of the Cretaceous, when the trough and its eastern 

 borderland were almost completely broken uj) and faulted into the depths 

 of the Indian Ocean. 



Graben are also downfaulted areas, but of much smaller dimensions. 

 They may develop on any part of a folded land. 



FOUNDERING OF BORDERLANDS 



The borderlands of North America are pictured in figures 2 and 3. 

 These show that North America in Proterozoic time was 2,000,000 

 square miles larger than it is now, and that Appalachia in the Devonian 

 extended not less than 250 miles beyond the present shoreline. Now the 

 •eastern part of this land is warped at least 5,000 feet into the depths of 

 the Atlantic. On the other side of North America the outer parts of 

 Oascadia have been warped and probably in the main faulted into the 

 Pacific to depths of 14,000 feet. 



During the Paleozoic and the earlier half of Mesozoic time the west 

 coast of South America appears to have extended at least several hundred 

 miles beyond the present shoreline, and some of this old land remains 

 along the coast of Chile. Off Peru the Andes borderland has gone into 

 the abyss an3^where between 13,000 and 24,800 feet, and this seemingly 

 since middle Pliocene times. While this foundering was going on, the 

 peneplaned Andes were raised vertically not less than 10,000 feet, a dif- 

 ferential movement between the elevated and depressed masses amounting 

 to nearly 7 miles. 



FOUNDERINGS OF CONTINENTS 



It is now widely admitted that Madagascar, an island of 230,000 square 

 nailes area, was once a part of Africa, and yet today it is separated from 

 the latter by Mozambique Channel, from 210 to 600 miles wide, with 

 depths down to 11,800 feet. Madagascar is, however, only the southern 

 end of far greater Lemuria, a land of Mesozoic and older times that ex- 

 tended northeasterly, taking in all of peninsular India. Of this conti- 

 nent, there is left Madagascar, India, and groups of islands (Seychelles, 

 Comoro, etcetera), Avith oceanic depths between them varying from 13,650 

 to 17,380 feet. 



The greatest of all foundered continents, however, is the ancient Meso- 

 zoic land named by Neumayr Sino-Australia, embracing southeastern 

 China and Siam, Sumatra, Java, Borneo, Celebes, the Philippines, New 

 Guinea, Australia, New Zealand, New Caledonia, the lesser Hebrides, the 

 Solomons, Fijis, and Samoas. Great areas of Sino-Australia have gone 

 into depths variable between 10,000 and 13,000 feet and in places to over 



