The Democratic press. [volume] (Ravenna, O. [Ohio]) 1868-1901, 1885-07-16
EARTHQUAKES.
Superheated Steam under great Pressure
Supposed to be the Direct Cause.

Supposed to be the Direct Cause.
1t has been asked of late whether the
hurricanes which followed the Spanish
earthquakes were not produced by
those subterranean disturbances, and
all-explaining electricity has been
called upon to explain how earth
throes might have caused atmospheric
disturbances. L know of no way in
which such consequences could have
followed from displacement of the
earth's crust. To me it seems far more
natural to conclude that the hurricanes
and earthquakes were alike produced
(the hurricanes chiefly. the earthquakes
partially by the atmospheric compress
sion which preceded the subterranean
disturbances. This compression indi-
Gated heaping of air over the dis
turbed region; the earth's crust yielded
under this increase of pressure, COM
bined with the action of other forces,
and earthquakes followed; the COM
pressed air swept away to regions of
less pressure. and the rarefaction fol-
lowing led in the usual way to the in
draught which precedes cyclonic dis
turbance in the air.
But while the action of atmospheric
pressure in helping to excite subter-
ranean activities must not be over
looked, the varying pressure exerted
by seas and oceans is a more potent
disturbing factor. Atmospheric press
ure is distributed in such way that
though the weight of air on any
given area is continually changing,
there are no sharply defined lines, at
s4A
less pressure from regions of greater
pressure. 1t is otherwise with the sea
along shore line. Here we have the
sea acting with constantly varying in
tensity. as its level changes, on the sea-
ward side of the shore line, while on
the landward side there are no such
variations of pressure. Let US consider
what this means. Take a tolerable
straight shore line 500 feet in length,
and suppose that along this shore line
a region of ocean 100 miles broad rises
through a height of three feet under
the combined action of sun and moon
raising q tidal wave, and favoring
strong winds urging the water shore
ward. Then we have $4,000 square
miles of sea-water, three feet deep,
added as so much dead-weight to that
part of the earth's crust which under
lies the seas along the shore. Each
square mile contains in round numbers
5000, 900 square yards, or $1,000, 900
square feet. The additional weight
corresponds, then Gas the added layer
is three feet deep), to so, 900 times
100000 cubic feet of water. each
weighing 635 pounds, or to 16,OOO,-
900, 900 tons. 1t is clear that the addi-
tion of so enormous a weight as this to
the submerged part of the earth's crust,
outside the shore line. may well pro-
duce strains too great TO be resisted.
1t must be remembered that the very
existence of a precipitous shore line
Gas distinguished from one where the
land above water and the parts sub
merged form one great slope) indicates
the comparative weakness of the crust
along the coast 1t has Welded on one
side TO pressure thrusting it upward
above the sea-level, and on the other
side to the pressure of the water fore
ing it down. 1t is true, the actual
line of yielding may not coincide with
the existent shore line. For the action
of the sea waves may (and generally
must) have altered the position of the
coast from that which it occupied when
first formed. But it may be taken for
granted that not far from every precipi-
tous shore line lies a line of weakness,
where the crust has given way in the
past. and may give way again. In this
consideration undoubtedly we find q
part of the explanation of the observed
fact that almost all the great regions of
subterranean activity on the earth lie
near the sea-shore.
But while the changes of atmospheric
and oceanic pressure are potent factors
n the production OF earthquakes, and
are probably in the great number of
cases their direct occasion, it is, of
course, to the snbterranean regions
themselves that we must look for the
forces at work in upheaving the crust
of the earth. The forces acting from
the outside are as the pull ON the trig-
ger; the imprisoned gases and vapors
generated by internal heat are as the
powder by whose explosion the missile
is elected.
Yet even in considering the earth's
subterranean activities We still have to
look outside for part at least of the
causes of disturbance. The air perhaps
may in this respect be neglected, but
the water is .all-important. 1t has been
said, indeed, and probably with a
nearer approach to truth than usual i'll
the case of generalizations of the sort,
without water there can be no volca-
no." and q similar rule mot quite so
generaD applies to earthquakes: few
probably occur, possibly none, save
through the action of water in some
way or another. All active volcanoes
except one (in mid-Asia) are by the
sea-shore. Nearly all the great earth
quakes recorded by history have taken
place, and have apparently had their
centre of disturbance, near the sea.
There can be very little doubt, in
deed, that the direct cause of every
great subterranean disturbance is wa
ter in form of steam-steam super
heated, under great pressure, and
therefore possessing much greater ex-
pansive power than steam at ordinary
temperatures. Richard A, Proctor, IN
Harper's Magazine for June.