The Mount Holly news. [volume] (Mount Holly, Burlington Co., N.J.) 1891-1942, 1910-05-31
BIRTH OF A VOLCANO.
Natures Process In Forming a
Mountain of Lava.
THE FORCE OF AN ERUPTION.

oPheavai That Destroyed the East
Indian Island of krakatoa In 1888
propelled an Air Wave Three and q
Half Times Round the Earth.
Enough volcanoes are often spoken
or as burning mountains, they do not
Durn at all, nor, in the proper sense of
tne word, are they mountains at all.
volcano is really flaw In the crust
OF the earth through which the fierce
glowing heat lying below the crust has
managed to burst hole Through this
mole great floods Of melted rock spout
up. Some volcanoes work at inter-
walls; some are in eruption all the time.
AS the melted rock jets up into the
air and falls it naturally builds itself
into mountain round the hole. The
next eruption has to burst its way
through the heart of that mountain.
The chimney it spouts through is usu-
ally called 1.-The pipe"
sometimes an eruption is so fierce
that when the lava another name for
melted rock spouts out it is burst into
bits. When it falls it is sometimes as
f1ne as dust, sometimes the size of Gin
ders. Most volcanoes, indeed, are sim
ply gigantic cinder heaps.
When the force is not so great the
lava in the pipe simply bubbles over
and flows down the sides Of the noun
tain, exactly as porridge boils over the
edge Of pot. As lava is liquid, the
slope Of lava volcano Tor lava cone
as it is usually called is always very
gentle. Falling cinders, on the other
hand, pile themselves up quite steepIy.
A lava cone, then, is always less steep
than a cinder cone.
And volcano never burns. What
looks like fame is only the glow Of
the white hot lava on the clouds OF
steam. The more steam there is fore
ing its way up the pipe the more the
lava bubbles, just as In the case Of
the porridge. If the pressure Of steam
is very great, then you havesthe lava
blown to bits and falling as cinders,
while the mighty clouds of steam rise
high above the mountain. 1t is this
steam that is mistaken for smoke.
Sometimes a cone sends out lava and
cinders alternately, so that you have
a great mountain of cinders bound to-
gether by layers and walls of lava.
These walls of lava are due to the
fact that sometimes more lava wants
to come up the pipe than the pipe will
hold, so the lava bursts its way out
through weak spots in the sides of the
mountain. Etna has no fewer than
TOO Of these cones on its slopes. One
Of them, Monte Rossi, is a hill in
itself, being $50 feet high. Indeed, a
model of Etna looks as If it were COW
cred with pimples.
When Etna is really reused it is far
more dangerous than Vesuvius. In
1859 it nearly destroyed the city of
Catania, killing $4,000 people. In 1869
it found its pipe so independently
small that it had to crack one Of its
sides. This crack was no less than
twelve miles long. At the bottom
white hot lava could dimly be seen
through the clouds Of steam. In 1855
millions of gallons Of boiling water
were shot out of the Val del Bove,
which is a great circular pit on the
slope Of the mountain, four or five
miles in diameter, its sides being cliffs
nearly a. mile high in places
The greatest volcanic eruption ever
known took place in the East Indies
in 1888. The story makes almost in
credible reading. The volcanic island
of Krakatoa commenced proceedings
by blowing half of itself into thin air.
From the opening no less than cubic
mile of rock was shot out.
A column of steam and lava dust
rose into the air to a height six times
as great as that of Mount Everest 1t
spread and spread till for hundreds of
miles around the air was black as mid |
night Sounds as of distant cannonad |
ing were heard 1900 miles off.
Sea waves fifty feet high killed 49,, |
900 people and were felt as far off as |
California. Instead of an island half |
a mile high there was now hole |
quarter Of mile deep. The shock of |
the eruption sent air waves three and |
q half times around the earth The |
fine dust in the upper atmosphere add |
ed for months afterward strange |
glow to the sunsets in England and |
did not vanish completely for three
years.
The exact cause of the eruptions is |
not known for certain. A popular the
DRY is that they are caused by water |
getting in to the white hot mass which |
is supposed to lie under the outer crust |
of the earth. And it is certainly a fact |
that practically all volcanoes are close
to the edge of the sea.
Some lava flows slowly, some quick |
ly. Vesuvius in 1905 sent out lava |
stream that in four minutes had reach |
ed spot four miles off. The size of |
lava stream is sometimes gigantic. In |
1888 Skaptar Jokull in Iceland emitted |
two streams at one time. One was |
forty miles long by seven miles broad, |
the other fifty miles by fifteen. The |
average depth Of both was about a
hundred feet.
Lava cools very, very slowly, except |
on the surface, which cools at once. |
1t is an extremely bad conductor Of |
heat. Twenty years after a stream Of |
lava was sent out from Jorullo, In Mex
leo, tourists could light their cigars |
through chinks in the surface, and the |
surface had been cold for twenty years. |
In 1928 a layer Of snow many feet !
thick was found under layer of Vesu- |
Wan lava. 1t was still unmelted and |
is probably there still = Pearson's |
Weekly.
The Praetorian Guard