F. A, Ferret — Lava Eruption of Slromboli. 449 



Before this eruption, this had been a very small but active vent 

 situated on the eastern parapet, with a notable tendency to 

 collapse of its walls, giving thus, in its frequent explosions, 

 dense clouds of detritus. At present it is one of the great 

 mouths of the eruptive apparatus, as it has always been one of 

 the most active. 



Bocca C — by far the largest of the four — is situated next to 

 the westerly Faraglione, while Bocca D, which is generally the 

 least active and recently was obstructed for the greater part of 

 the time, lies east of C and more or less directly south of the 

 enlarged B. 



At the beginning of this eruption the lava overflowed the 

 lower lip of the crater, forming and leaving a consolidated, 

 convex ridge, probably a tunnel ; later it issued from lateral 

 vents on the slope of the Sciara. Owing to lack of observa- 

 tions made at the time, we shall probably never be able to 

 reconstruct this phase of the eruption. Near the central line 

 of the Sciara and starting from Bocca A there is a fracture 

 open at the surface for at least two hundred meters, of which 

 the two edges are at different levels, but if the lava ever issued 

 from this the locality has become hidden beneath later flows 

 from ihe mouth which formed during the month of November. 

 This is situated to the west of the fracture and about 160 meters 

 from the crater and therefore at a level perhaps a little more 

 than a hundred meters below the edge of Bocca A. 



This aperture has the usual form of an " oven mouth," and 

 is nothing more than the extremity of a tunnel which conducts 

 the lava from the interior. 



From this disposition of the eruptive apparatus there results 

 an effusion of lava which is in the nature of an overflow, not- 

 withstanding the fact that it issues from a lateral opening, inas- 

 much as it is an outflow of material from the upper portion of 

 the magmatic column — a "sub-aerial" effusive eruption. And 

 this disposition further permits, and produces in its perfection, 

 that separation and segregation of gas and liquid — the first 

 rising and escaping through the central crater, and the second 

 flowing out laterally — which so greatly affects the character of 

 an eruption, as was demonstrated at Teneriffe* and at Saku- 

 rashimaf and, as we shall presently see, also here at Stromboli- 



The Fluent Lava. 



As a result of the disposition just referred to, the lava issues 

 from its tunnel already freed of those large bubbles of gas at 



* The Volcanic Eruption at Teneriffe in the Autumn of 1909, Frank A. 

 Perret, Zeitschr. f. Vulkanologie, i, p. 24, 1914. 



f Sakurashiuia, Eapporto prelirninare per l'istituto vulcanologico sulla 

 grande eruzione del valcano Sakurashima, Gennaio, Febbraio, Marzo, Aprile, 

 1914, Zeitschr. f. Vulkanologie, i. p. 137, 1914. 



