June 2, 1910J 



NA TURE 



;99 



THE RECEXT ERUPTION OF A/OLAT ETNA. 



EVERY eruption of Mount Etna since 1883 has 

 taken place on its southern slope. The erup- 

 tion of 1S83, which was preceded and accompanied by 

 verv severe earthquakes, caused a radial fracture, 

 running roughly from north to south, from the cen- 

 tral crater to an altitude of 950 metres on the afore- 

 said slope ; but that eruption was abortive, only last- 

 ing three days, and forming ven,- small craters and 

 insignificant flows of lava. 



The eruption of 1886 took place on the same frac- 

 ture of 1883, without any severe earthquakes. A 

 large crater was formed, a great mass of lava was 

 expelled, and the eruption lasted twenty days. 



The eruption of 1892, on the same fracture of 

 1883. was preceded and accompanied by a few slight 

 earthquakes ; it formed four large craters and other 



figures approximately giving the altitudes of the 

 middle of the eruptive areas : — 



Eruption of 1883 : al.itude 1050 m. 



,, 1886: ,, 1450 m. ; difference 400 m. 



„ 1892 : ,, 1850 m. ; ,, 400 m. 



1910: „ 2175 m.; „ 325 "• ' 



This suggests, therefore, that successive eruptions 

 break out on the same fracture, but each higher than 

 the last. This is easily explained by the fact that the 

 lava of an eruption, tending to flow down, within and 

 upon the fracture, closes it in the lower part, and 

 leaves it more or less open in the higher, where, con- 

 sequently, another eruption may be produced more 

 easily. 



We now come to the recent eruption. From the 

 early hours of March 23 until 8h. 15m. a.m., the 



Fig. I. — Eiuption of Etna seen from the heights X.-X.E., April 4, 1910. Photograph by .\ssistant L. Taffara. 



small craters, emitted still more lava than the erup- 

 tion of 1886, and lasted six months. Thus during 

 these two eruptions it appeared that the lava found a 

 passage prepared, whence its emission was easy. 



During the month of .\pril, 1908, there was an 

 eruption on the eastern slope of the Valle del Bove ; 

 it was accompanied by a few slight earthquakes, but 

 no raised craters were formed, little lava was ex- 

 pelled, and the disturbance lasted less than twenty- 

 four hours. Evidently this also was an abortive 

 eruption, probably because (as it did not take place on 

 the fracture of 1883) it found no free opening for 

 the emission of the lava, and met instead the unyield- 

 ing rocks of the higher parts of the Valle del Bove. 

 If we consider only the eccentric eruptions, those 

 which have taken place since 1883 (including the re- 

 cent eruption, which, as will be seen, is on the same 

 radial fracture as the others), we find the following 



NO. 21 18, VOL. S^l 



seismographs of the Observatory of Catania registered 



many slight shocks, which followed one another almost 



\ continually. Of those which in the large seismograph 



! had an amplitude (2a) greater than i mm., there were 



twelve, the severest of which (20=13 mm.) took 



: place at 2h. 55m. a.m. But even this last shock was 



not felt by the inhabitants of the villages nearest the 



place of the eruption, so that it did not raise any 



alarm. These circumstances, together with the fact 



; of its being night and everyone asleep, prevented any- 



' thing abnormal being observed on the volcano until 



8h. 15m. a.m. At this hour, rising above the mist 



and above the Piano del Lago, a thin column of 



steam was seen, widening at the top and taking the 



characteristic form of a pine {Pinus italicus). In 



fact, a large fracture had been formed, having a 



length of almost 2 kilometers, from Monte Castello 



to the western base of the Montagnola, in the direc- 



