Wessington Springs herald. (Wessington Springs, Aurora County, Dakota [S.D.]) 1883-1891, 1884-09-26
Why the Earth Quakes.

While facts enough regarding the ex
tent of the earth quake OF Sunday have
not come to hand TO enable me to speak
on the direction of the earth wave OF
its peculiar features, as compared with
other earthquakes. yet something may
be said as to the latest convictions 81
students of science on the nature of the
earth below the point any man can
penetrate. That may lead us to guess
intelligently at the cause of earth.
ouakcs.
You know the long received theory
of the nature of the interior of the earth
was that it is a molten mass, and that
we move around on a crust enveloping
the earth and caused by the cooling oil
of THIS mass ON the outside. 1t is un.
doubtedly true that about thirty miles
below the earth's surface the tempera-
ture is so high that everything is in a
melted condition. We know this. be.
aus we have learned that every fifty
feet we penetrate into the earth there is
an increase OF temperature OF about one
degree, and at q distance of thirty
miles the heat is SO great that any sub
stance we know of would melt. Per-
haps the melted mass is in the form of
9 liquid. That would be certain but
Tor the immense pressure on it. The
pressure is estimated at 10000 tons on
a square loot. OF course. scientific
men can not experiment with matter at
a high temperature with a pressure OF
10000 tons TO a square foot, 50 we can
only guess what may be its condition.
In talkin" about this melted mass thir-
ty miles under us. the term water sub
stance is used by BIOLOGISTS.
'How great is the distance through
this water substance we do not know,
but it is certain that its density in
creases more and more, gradually, I'M
til the interior of the earth is solid.
probably, from the inconceivab'e pres
sure LOO, 1900, or 5000 miles from
the surface. Sir William Thompson
has demonstrated that the earth
must have a core much denser
than the land and water we live on.
He points out the fact that il Il shell
only thirty miles thick surrounded 4
molten liquid mass extending from one
side of the carth through the center
to the other side, then the moon.
through the law Of gravitation, would
displace the liquid or gas in the inter
ior of the earth TO such an extent that
the earth's Crust would bulge out in
the direction of the moon, making u
tide in the solid crust of the earth, as
certainly as the skin of an orange
bulgcs out when you squeeze the fruit
between the palms Of your hands.
And this would be evident to us be-
aus the ocean tides would be almost,
if not quite. imperceptible to us. TO
Withstand the attraction Of the moon.
the earth, Sir William says, must be as
rigid as steel.
80 we have the theory that the crust
OF the earth floats on and imposes an
immense weight on Il water substance,
which is inconceivably hot. Now, as
to the way an earthquake may be
caused. suppose moisture tricklcd
gradually, year after year, through this
crust into the heated mass. In our at
mosphere steam would be pro-
duced. Thirty miles below us
the pressure is SO great that it
is not likely that steam could be
generated. One thing, though: the pres
sur of 10000 tons to the square foot. a
pressure eSerted in every direction,
would be increased. Some effect must
be produced down there, and it is easy
to see that if one place in the earth's
crust is weaker than another near the
region where the water tri Killed. in, then
the weakest place muststan' the strain.'
1t is not unreasonable to suppose that
this pressure below might be so great
that the earth's covering was shifted a
little 10 adapt itself to the pressurefrom
below. This shifting of the crust is, in
tact, the earthquakes.
believe this theory has the greater
reason on its side,' because earthquakes
are almost always in the re.ion of vol
canoes, and volcanoes are almost al
ways in or nea the ocean.
Another theory of earthquakes is that
as the earth is very gradually cooling
OFT, the crust is thickening on the un-
der side, and cracks or assures on the
under side OF the crust many miles deep
may g in consequence OF the enor-
nous pressure, SO that the water rushes
into a new position with Il force that
would knock u continent out of shape
IT it took place on the earth S surface.
That motion would be sufficient to pro-
duce Il vibration thirty miles distant.
Whatever the cause of the recent
earthquake, l think the earth in the re-
gion where it took place has either set
tied INTO u new position or is forced
back into an old position from which it
was pushed by former earth luakes.-
l'rot. Merr1nan, Of hutge1'S College.