864 PRINCIPLES OF STRATIGRAPHY 



pies of such cinder-cones rising from the abyssal sea-bottom are 

 unknown. 



The Mediterranean has been the region best known for sub- 

 marine volcanic eruptions. Of these a number have been of the 

 explosive type, though more generally the compound (explosive 

 and extravasative) type prevailed. The most noted of the recorded 

 submarine eruptions "occurred in the year 1831, when a new vol- 

 canic island (Graham's Island, He Julia) was thrown up, with 

 abundant discharge of steam and showers of scoriae, betv/een 

 Sicily and the coast of Africa. It reached an extreme height of 

 200 feet or more above sea-level (800 feet above sea-bottom) with 

 a circumference of 3 miles, but, on the cessation of the eruption, 

 was attacked by the waves and soon demolished, leaving only a 

 shoal to mark its site." ( Geikie-9 :^50.) "The upper part of this 

 volcanic cone, above the sea at least, seemed to have been solely 

 composed of ashes, cinders, and fragments of stone, commonly 

 small. Among these fragments of limestone and dolomite, with 

 one several pounds in weight, of sandstone, were observed. (De 

 la Beche-6:p5.) These fragments were broken ofif from the rocks 

 through which the eruption passed on its upward way. "During 

 the time that this volcanic mass was accumulating, a large amount 

 of ashes and cinders must have been mingled with the adjacent sea 

 before it reached its surface, and no slight amount would be dis- 

 tributed around, when ashes and cinders could be vomited into the 

 air. Add to this the quantity caught up in mechanical suspension 

 by the breakers and there would be no small amount to be accumu- 

 lated over any deposits forming, or formed, on the bottom around 

 this locality . . ." (De la Beche-6 :p5, p6). These deposits in- 

 cluded, of course, abundant remains of organisms, killed by the ex- 

 plosive eruption. Another example of a volcano formed in the his- 

 toric period is Sabrina Island in the Azores, ofif the coast of St. 

 Michaels. Here a submarine eruption built a cone of loose cinders 

 to a height of about 300 feet, and a circumference of about a mile. 

 This, too, soon disappeared under the subsequent attack of the 

 waves. 



"The formation of this island was observed and recorded. It 

 was first discovered rising above the sea on the thirteenth of June, 

 181 1, and on the seventeenth was observed by Captain Tillard, 

 . , . from the nearest cliff of St. Michael's. The volcanic bursts 

 were described as resembling a mixed discharge of cannon and 

 musketry ; and were accompanied by a great abundance of light- 

 ning." (De la Beche-6 i/i"?.) A sketch made at that time is here 

 reproduced (Fig. 229). A similar occurrence is recorded from 



