It is but rarely that the elastic forces at work within the interior of
our globe have succeeded in breaking through the spiral domes which,
resplendent in the brightness of eternal snow, crown the summits of the
Cordilleras; and even where these subterranean forces have opened a
permanent communication with the atmosphere, through circular craters
or long fissures, they rarely send forth currents of lava, but merely
eject ignited scoriæ, steam, sulphuretted hydrogen gas, and jets of
carbonic acid.--_Humboldt’s Cosmos_, vol. i.