The amount of the elevating force is manifested
p 229
by the elevation of the volcano, which varies from the inconsiderable height
of a hill (as the volcano of Cosima, one of the Japanese Kurile islands) to
that of a cone above 19,000 feet in height. It has appeared to me that
relations of height have a great influence on the occurrence of eruptions,
which are more frequent in low than in elevated volcanoes. I might instance
the series presented by the following mountains: Stromboli, 2318 feet;
Guacamayo, in the province of Quixos, from which detonations are heard
almost daily (I myself often heard them at Chillo, near Quito, a distance of
eighty-eight miles); Vesuvius, 3876 feet; Aetna, 10871 feet; the Peak of
Teneriffe, 12,175 feet; and Cotopaxi, 19,069 feet. If the focus of these
volcanoes be at an equal depth below the surface, a greater force must be
required where the fused masses have to be raised to an elevation six or
eight times greater than that of the lower eminences. While the volcano
Stromboli (Strongyle) has been incessantly active since the Homeric ages,
and has served as a beacon-light to guide the mariner in the Tyrrhenian Sea,
loftier volcanoes have been characterized by loong intervals of quiet. Thus
we see that a whole century often intervenes between the eruptions of most
of the colossi which crown the summits of the Cordilleras of the Andes.
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