The Redwood gazette. [volume] (Redwood Falls, Minn.) 1873-1940, 1907-12-04
THE EARTH'S INTERIOR
Our Planets Core Is Liquid, Yet
It's as Rigid as Steel.
UNDER ENORMOUS PRESSURE

Neither Rock Nor Metal Could Remain
There In the State In Which We See
1t on the Surface-The Lava That
Breaks Through the Earth's Crust.
The idea that the interior of the globe
Is composed of flowing lava has long
dnce been abandoned, but the picture
that modern science offers of the in
side of the earth is hardly less ap-
palling. All investigations unite to
prove that the heat increases as we de-
scend deeper in the terrestrial crust
at such rate that forty or fifty miles
down no substance with which we are
acquainted could remain unmelted And
yet the same science tells us that the
core of the globe is enormously more
rigid than the hardest steel. This ap-
parent contradiction is due to the ire
mendous pressure inside the earth. No
rock and no metal can remain there in
the state in which we see it on the sur
face. It's molecules must lose the adj
herence characteristic of solid bodies
in consequence of the heat, but still
they are not free to flow like an ordi-
nary liquid, because of the compression
to which they are subjected.
The phenomena Of earthquakes have
given wonderful information about the
servations show that the shocks of
earthquakes are confined to a thin up
per shell. They originate at a depth
of only few miles at the most. But
the vibrations which they set going
are felt all through the earth, often ex-
tending to the antipodes. The great
core, held rigid by the pressure, is ex-
tremely elastic, and it responds to a
shock like ball of steel or of glass.
The density of the earth increases to-
ward the center. 1t is only in the up
per part of the crust that local move
ments can take place, causing shocks
and changes of level at the surface.
Deeper down everything is gripped and
immovable, except, as already re-
marked, that the molecules Of the rocks
and metals there are subject to vibra-
ton like those Of bell against which
a blow is struck
But this is not all. Whenever a local
release from the pressure is brought
about by changes near the surface the
potentially liquid but effectually solid
core at that point may suddenly be-
come fluid and gush forth through a
volcanic throat or other vent. But
such effects cannot extend to any great
depth. Nothing comes to us from the
vast interior mass. That remains a
perpetual mystery, far beyond the
searching hand Of science. Indirectly,
however, we may learn much about it.
Astronomical considerations throw
great deal Of light upon the subject.
We see that through the planetary sys-
tenn rotating globes are fattened at the
poles. The same thing is true of the
earth. It's equator bulges; it's polar
regions are drawn inward. Mechan-
ical laws assure us that the cause is
to be found in the fact that the earth
and the other planets have assumed
shape under the influence Of the cen
trifugal force of their rotation. That
force is necessarily greatest at the
ten bodies, they have commenced to So
lidify at the surface after having as
sumed an ellifordal form due to their
rotation.
Another very significant fact is that
the shape of the earth corresponds with
that which a globe rotating with its
velocity would have If composed of
materials arranged to their density
that is to say, growing denser toward
the center. The heaviest materials
must be deep down in the globe; the
lighter materials have remained at the
surface. This again corresponds with
the facts Of observation. We know
the total weight and the average
density Of the earth. 1t weighs" six
sextillions of tons, and its average
density is five and half times that of
water. But the substances composing
the crust of the earth have an average
density of twice that Of water. 1t
follows that the heaviest things in the
earth, on the average, exist deep with
in its exterior For all that we can
tell, it's inner core may be wholly me-
tallic. At the center there is probably
an enormous aggregation of dense me-
tallic substances.
An indication that the inner parts of
the earth consist largely If not mainly
or iron is to be found in the mag
netism of the globe. The earth is
great permanent magnet. If we could
learn the facts it might turn out that
iron is the most abundant substance
in the solar system and perhaps in
the whole universe. The majority of
the meteorites that fall upon the earth
consist Of solid iron. Blow the earth
to pieces and in the resulting cloud
Of fragments the rocks that we are
familiar with would be almost imper-
ceptible. There would be a rain Of