THE NATURE OF VOLCANIC ACTION. 

 By Reginald A. Daly. 



Presented April 12, 1911. Received February 23. 1911. 



Contents. 



Page 



The Problem 48 



Abyssal Injection 50 



Conditions of Abyssal Injection 52 



The Substratum 54 



Some Direct Consequences of Abj'ssal Injection 55 



Genetic Classification of Volcanic Gases 57 



Phases of Volcanic Action 58 



Fissure Eruptions 58 



Eruption through Local Foundering 60 



Blue Hills, IMa.ssachusett3 62 



Glen Coe, Scotland 62 



Yellowstone National Park 63 



Central Eruptions , 67 



Opening and Localization of the Vent 67 



Enlarged Fissures 67 



Diatremes 69 



Plutonic Cupolas 69 



Continuance of Activity ; Analj'sis of Conditions at Kilauea ... 71 



Rate of Heat-loss through Conduction into Walls 71 



Rate of Heat-lo.ss through Radiation at the Crater . . . .v. . 72 



Methods of Heat Transfer 73 



Two-ph;i.so Convection 76 



Lava Fountains 82 



Cooling by rising Juvenile Gas 84 



The Volcanic Furnace 85 



Summary of the Heat Problem of an Active Central Vent. . . 90 

 Revival of Activity at the End of a Dormant Period ; Periodicity 



of Volcanoes 92 



Small Size of Central Vents 97 



Explosive Types ; Phrcatic and Magmatic 100 



Magmatic DifTcrcntiation at Central Vents 102 



Progr&s.s in E.xplosivcncss at the Greater Vents 105 



Lava Outflow at Central Vents 106 



The two Types of Lava Flows 107 



