THE ERUPTION OF VESUVIUS IN APRIL, 190G." 



By A. Lacroix. 



CONTENTS. 



Page, 



I. Effusion of, lava and explosive phenomena _ 223 



General types of volcanic eruption 223 



Sequence of phenonaena of the eruption 225 



Effusion of lava 227 



Explosive phenomena 230 



Strombolian explosions , 230 



Vulcanian explosions 230 



Formation of a caldera 231 



Dry avalanches - 232 



Partial destruction of Ottajano and San Giuseppe 233 



Fall of ash 234 



II. Fumaroles and products of eruption 235 



Fumaroles - 235 



Fumaroles of the lava _ 236 



Fumaroles of the fissures and of the crater 237 



Secondary fumaroles 238 



Exhalations 239 



Other phenomena - 239 



Earth movements 2.39 



Electric phenomena 239 



Mud torrents. . - . . 240 



Products of eruption 241 



New magma .' . . . 241 



Products of the vulcanian explosions - 243 



Lapilli 243 



Breccias 243 



Conclusions • 246 



I. — Effusion or Lava and Explosive Phenomena. 



GENERAL TYPES OF VOLCANIC ERL'PTIONS. 



A preliminary statement is necessary regarding the different types 

 of volcanic eruptions. 



The chemical composition of a magma is believed to be a more or 

 less dominant factor in the dynamics of eruptions; violent explosions, 



"Translation, in abstract, by permission of author and publisher, of article 

 in Revue genera le des Sciences, Paris, October 30, 1906, pp. 881-899 ; November 

 15, 1906, pp. 923-936. 



223 



