THE VOLCANO ASO AND ITS LARGE CALDERA 



501 



ing diagram is largely from memory and is intended merely to convey 

 a general idea of the caldera. 



GEOLOGY OF KIUSHIU 



The island Kiushiu, which covers about 17,000 square miles, has a 

 foundation of rocks of Paleozoic age and possibly some belonging to 

 the Archaean. These are largely sedimentary, and frequently meta- 

 morphic; but associated with them are many varieties of igneous 

 rocks. Less altered strata of supposed Mesozoic age, but possibly 





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V^^c''«W'-',^ 



Fig. I. — Sakura-jima, an andesitic cone of medium slope, in the bay of Kagoshima 

 at the southern end of Kiushiu. Its last eruption was in 1779. Its altitude is 3,850 

 feet. • - 



in part representative of the early Tertiary, overlie these extensively; 

 and fossiliferous, much-disturbed Tertiary formations occur in 

 numerous relatively small detached basins. Over these basement 

 rocks a superstructure of eruptives has been built up during the 

 Quaternary,' having probably been begun before the close of Tertiary 

 time. About one-half of the island is now covered by these volcanic 

 rocks. In some places the covering has the nature of a thin layer 

 of ash or volcanic mud or lava over the old surface, whereas in others 

 it has a great thickness. The whole of the north-central part of the 



