CONTENTS. 



Page 



I. Introduction 1 



Geogi'apliic Sketoli 2 



Previous Work 5 



H. Structure and Morpholoj^y 11 



Sti'uctm-al Outline 11 



Building Materials of tlie Somma 13 



Steep Slope aloug the East Coast 1(5 



Vulcanism ou tlie Flauks <jf the Somma 18 



The Caldera 2r> 



The Central Coue 2î> 



Small Demolished Igneou Bsodies along the Wastern Half of 



tlie Northern Coast 38 



Explanation of the Present Features 44 



m. Volcanic Activity in Historic Times 53 



IV. Petrography 60 



Some Specially Devised Petrogi-aphic Methods 62 



Special Descriptions 67 



A) La^'as (:)f the Somma <>7 



B) Lavas of the Central Cone 7«^ 



C) Hocks constituting the Demolished Igneous Bodies 



along the Western Half of the Northern Coast . . 88 



D) Kocks occuiTing as Dykes 94 



E) Ejecta 9(> 



V. History of the Magma 101 



Probable High Fluichty of the Magma of Oshima 10;-5 



Separation of a Mix-Crystal Series 104 



CiystaUization of the Component Minerals 10<> 



Summary on the Cooling History of the Magma HG 



Development of the Various liock -Types 118 



VI. The Geologic Position 125 



Vn. General Summary 14^1 



