VOLCANOES
“IT is not late yet, Uncle,” said Jules; “you ought to tell us about
those terrible mountains, those volcanoes that the showers of ashes come
from.”
At the word “volcano,” Emile, who was already asleep, rubbed his eyes
and became all attention. He too wanted to hear the great story. As
usual, their uncle yielded to their entreaties.
“A volcano is a mountain that throws up smoke, calcined dust, red-hot
stones, and melted matter called lava. The summit is hollowed out in a
great excavation having the shape of a funnel, sometimes several leagues
in circumference. That is what we call the crater. The bottom of the
crater communicates with a tortuous conduit or chimney too deep to
estimate. The principal volcanoes of Europe are: Vesuvius, near Naples;
Etna in Sicily; Hecla in Iceland. Most of the time a volcano is either
in repose or throwing up a simple plume of smoke; but from time to time,
with intervals that may be very long, the mountain grumbles, trembles,
and vomits torrents of fiery substances. It is then said to be in
eruption. To give you a general idea of the most remarkable phenomena
attending volcanic eruption, I will choose Vesuvius, the best known of
the European volcanoes.
“An eruption is generally announced beforehand by a column of smoke that
fills the orifice of the crater and rises vertically, when the air is
calm, to nearly a mile in height. At this elevation it spreads out in a
sort of blanket that intercepts the sun’s rays. Some days before the
eruption the column of smoke sinks down on the volcano, covering it with
a big black cloud. Then the earth begins to tremble around Vesuvius;
rumbling detonations under the ground are heard, louder and louder each
moment, soon exceeding in intensity the most violent claps of thunder.
You would think you heard the cannonades of a numerous artillery
detonating ceaselessly in the mountain’s sides.
“All at once a sheaf of fire bursts from the crater to the height of
2000 or 3000 meters. The cloud that is floating over the volcano is
illumined by the redness of the fire; the sky seems inflamed. Millions
of sparks dart out like lightning to the top of the blazing sheaf,
describe great arcs, leaving on their way dazzling trails, and fall in a
shower of fire on the slopes of the volcano. These sparks, so small from
a distance, are incandescent masses of stone, sometimes several meters
in dimension, and of a sufficient momentum to crush the most solid
buildings in their fall. What hand-made machine could throw such masses
of rock to such heights? What all our efforts united could not do even
once, the volcano does over and over again, as if in play. For whole
weeks and months these red blocks are thrown up by Vesuvius, in numbers
like the sparks of a display of fireworks.”
“It is both terrible and beautiful,” said Jules. “Oh! how I should like
to see an eruption, but far off, of course.”
“And the people who are on the mountain?” questioned Emile.
“They are careful not to go on the mountain at that time; they might
lose their lives, suffocated by the smoke or crushed by the shower of
red-hot stones.
“Meantime, from the depths of the mountain, through the volcanic
chimney, ascends a flux of melted mineral substance, or lava, which
pours out into the crater and forms a lake of fire as dazzling as the
sun. Spectators who, from the plain, anxiously follow the progress of
the eruption, are warned of the coming of the lava-flood by the
brilliant illumination it throws on the volumes of smoke floating in the
upper air. But the crater is full; then the ground suddenly shakes,
bursts open with a noise of thunder, and through the crevasses as well
as over the edges of the crater the lava flows in streams. The fiery
current, formed of dazzling and paste-like matter similar to melted
metal, advances slowly; the front of the lava-stream resembles a moving
rampart on fire. One can flee before it, but everything stationary is
lost. Trees blaze a moment on contact with the lava and sink down,
reduced to charcoal; the thickest walls are calcined and fall over; the
hardest rocks are vitrified, melted.
“The flow of lava comes to an end, sooner or later. Then subterranean
vapors, freed from the enormous pressure of the fluid mass, escape with
more violence than ever, carrying with them whirlwinds of fine dust that
floats in sinister clouds and sinks down on the neighboring plain, or is
even carried by the winds to a distance of hundreds of leagues. Finally,
the terrible mountain calms down, and peace is restored for an
indefinite time.”
“If there are towns near the volcanoes, cannot those streams of fire
reach them? Cannot those clouds of ashes bury them?” asked Jules.
“Unfortunately all that is possible and has happened. I will tell you
about it to-morrow, for it is time to go to bed now.”
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