82 
NEWER PLIOCENE PERIOD. 
[Ch. VII. 
explosions. We may, therefore, suppose this volcanic action 
to have been as independent of the modern vents of Etna, as 
that which gave rise to the analogous formations in the Val di 
Noto. It is quite evident that the lavas of the Cyclopian isles 
are not the lower extremities of currents which flowed down 
from the highest crater of Etna, or from the region where 
lateral eruptions are now frequent, — lavas which, after entering 
the sea, were afterwards upraised into their present position. 
It is more probable that the basalts of the Bay of Trezza, and 
those along the southern foot of Etna, at La Motta, Aderno, 
Paterno, Licodia, and other places, originated in the same sea 
in which the eruptions of the Val di Noto took place. 
There are, however, as we have observed, no sections to 
prove that the central and oldest parts of Etna repose on similar 
submarine formations. The modern lavas of the volcano are 
continually extending their area, and covering, from time to 
time, a larger portion of the marine strata ; but we know not 
where this operation commenced, so that we cannot demonstrate 
the posteriority of the whole cone to these newer Pliocene 
strata. 
We might imagine that when the volcanos of the Val di Noto 
were in activity, and when the eruptions of the Bay of Trezza 
were taking place, Etna already existed as a volcano, the 
upper part only of the cone projecting above the level of the 
waters, as in the case of Stromboli at present. By such an 
hypothesis, we might refer the origin of the older part of Etna 
to the same period as that of the sedimentary strata and vol- 
canic rocks of the Val di Noto. 
But, for our own part, we see no grounds for inclining to 
such a theory, since we must admit that a sufficient series of 
ages has elapsed since the limestone of the Val di Noto was de- 
posited, to allow the same to be elevated to the height of from 
two thousand to three thousand feet, in which case there may 
also have been sufficient time for the growth of a volcanic pile 
like Etna, since the newer Pliocene strata now seen at the base 
of the volcano originated. 
