F. A. Perret— Lava Eruption of Stromboli. 447 



The Eruptive Apparatus. 



The formation, and the configuration of the crater of Strom- 

 boli conform to the same general type exhibited by other vol- 

 canoes, i. e. enlargement and abasement as effects of great 

 explosive paroxysms, interchanging with upgrowth and restric- 

 tion hs results of long-continued and moderate activity. It does 

 not exhibit, however, those colossal fault-block depressions of 

 calderal magnitude which are caused by rapid emptying of the 

 conduit through copious outpourings of lava at low levels. 

 But, inasmuch as the conduit of this volcano divides itself, at 

 the upper extremity, into various ramifications, and as the 

 normal activity is moderate and prolonged, the tendency is to 

 form a number of small crateral mouths — as many as seven, or 

 even more — crowning, as a rule, as many distinct conelets more 

 or less united into groups. 



And not even the most powerful and continued explosive 

 paroxysms of which we have knowledge — such as those in 1907 

 and 1912* — have been able to excavate any single crater 

 sufficiently profound to unite these several ramifications into 

 one single vent. In fact, although on both these occasions an 

 immense crateral cavity was formed, it was alwaj^s possible to 

 distinguish four different and distinct centers of explosion, 

 easily recordable by photography, and these have persisted as 

 principal vents during all recent phases of violent activity at 

 this volcano. I have designated them by the letters A, B, C, D. 



The actual crater consists of these four main divisions, 

 united in one great group with walls of separation which are com- 

 mon to the vents which are contiguous — four perfect craters, 

 that is to say, which occupy and fill the space of the great cra- 

 ter cavity of 1912. It is probable that these contain further 

 subdivisions, but in the conditions which prevailed during this 

 visit to the island this could not be determined with certainty. 



This conformation gives, as usual, a satisfactory measure of 

 the degree of explosive activity which occurred during this 

 phase, and one which here confirms the other observations, 

 viz., that the explosive activity was considerable but not by any 

 means catastrophic, the only truly paroxysmal explosivity hav- 

 ing been extremely limited in time. 



Bocca A, situated near the center of the upper edge of the 

 Sciara, is generally the most active, especially in those forms of 

 eruption which spring directly from liquid lava. It was the 

 source of the recent flows, and of nearly all the incandescent 

 ejections during the month of November. 



Adjacent to it, on the east, lies Bocca B, now much enlarged. 



*G. Platania: Ann. Uff. Centr. Met. Ital., xxx, p. 16 (1908), 1910. F. A. 

 Perret, Sci. Bull. Brooklyn lust., i, p. 813, 1907. F. A. Perret, Smithson. 

 Inst. Rep. (1912), p. 285, 1913. 



