454 F. A. Perret — Lava JEruption, of Stromboli. 



there was a submarine lava flow extending from beneath the 

 eastern lava held for a distance of two kilometers along the 

 sea bottom. The lava had a depth of some seventy-five meters, 

 with forty meters of water above it. The pressure at the sides 

 of this mass of lava near the bottom was, therefore, equivalent 

 to the weight of about 115 cubic meters of sea-water ( = tons 

 approximately) per square meter of area. The only disturbance 

 visible at the surface was a succession of convection currents 

 in the water, without eruption of gas, and without raising the 

 water temperature above 64° Fahr. at the surface and 72° 

 just over the lava. In this case, however, the entrance of the 

 lava into contact with water was mostly sub-surface and there- 

 fore removed from direct observation, so the Stromboli event 

 was welcomed as a rare opportunity for the study of this pheno- 

 menon. 



The best observations were made on Nov. 18 and 25, when 

 the sea and weather permitted — although with difficulty — an 

 approach to the base of the Sciara by boat, while the lava was 

 flowing into the sea in a massive, compact stream. This was 

 about twenty meters broad at sea-level, with moraines of another 

 twenty meters on either side, formed of the scoriae which slid 

 and rolled in avalanches down the side slopes of the convex 

 stream, amid clouds of brown attrition dust. 



The full length of the flow was visible, from the mouth of 

 emission to the place of disappearance below the sea, and 

 presented a striking spectacle, by day as well as by night. 

 The narrow upper portion, flowing rapidly down the slope in 

 a sinuous curve and slowly broadening, was divided on its 

 surface by a "medial moraine" of scoriae forming a black 

 streak between two ribbons of light — a phenomenon not un- 

 common in flows of this kind, as for example, Etna in 1910. 

 From the upper portion of the stream arose the familiar trans- 

 parent bluish vapor, which was replaced in the middle section 

 by the brown dust due to the attrition of scoria?, while from 

 the lower extremity arose the dazzingly white clouds of the 

 vaporized water at the point of entrance into the sea. 



The hot lava, with a front of twenty meters, entered the 

 water at an average rate of about three centimeters per 

 minute, but the area of contact between water and incandescent 

 lava, at any given moment, was rendered very variable by 

 reason of the strong sea swell which alternately invaded the 

 hot surface of the flow above mean water-level and then left 

 exposed to view the cooled surface below. The result was a 

 succession of strong steam puffs synchronous with the period 

 of the swell. 



It is interesting to note that, even with a perfectly calm sea 

 there is rarely a continnons and uniform evolution of vapor. 



