The new dominion. [volume] (Morgantown, W. Va.) 1876-1904, 1885-07-11
EARTHQUAKES.


Distin gufshed Scientists Opinion of the
Cause of subterranesn Activities.
1t has been asked of late whether the
hurricanes which followed the Spanish
earthquakes were not followed by those
subtcrranean disturbances. and ALEX
planning electricity has been called upon
to explain how earth-throes might have
caused atmospheric disturbances. l
know of no way in which such eonse-
quences could have followed from dis
placement of the earth's crust. To me
it seems far more natural 10 conclude
that the hurricanes and earthquakes
were alike produced (the hurricane
chiefly, the earthquakes partially by
the atmospheric compression which pre-
ceded the subterranean disturbances
This compression indicated heaping of
air over the disturbed region; the earth's
crust yielded under this increase of
pressure, combined with the action of
other forces. and earthquakes followed;
the compressed air swept away to re-
gions Of less pressure, and the rarefac-
ton following led in the usual way to
the indraught which precedes cyelonic
disturbance in the air.
But while the action of atmosl heric
pressure in helping to excite subterran-
can activities must not be overlooked,
the varying pressure exerted by seas and
oceans is a more potent disturbing fac
tor. Atmospheric pressure is distribu-
ted in such away that though the weight
of air on any given area is continually
changing. there are no sharply defined
lines, at any time, which separate re-
gions of 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 intensity, as its level changes.
on the seward side of the shore line,
while on the landward side there are no
such variations of pressure. Let us con-
slider what this means. Take a tolera-
bly, straight shore line 500 miles in
length, and suppose that along this
shore line region of ocean 100 miles
broad rises through height of three
feet under the combined action of sun
and moon raising a tidal wave, and
favoring strong winds urging the water
shoreward. Then we have $4,000 square
miles of 5ea-water. three feet deep, ad-
ded as so much lightweight to that part
of the earth's crust which underles
the seas along that shore. Each
sqnare mile contains in round num-
bers 100000 square Yards, or 81
100000 square feet. The addition
al weight corresponds. then Gas the
added layer is three feet deep.) to So
600 times $1,000, 900 cubic feet of water,
each weighing 64a pounds. or to 49,
OO0, 100000 tons. 1t is clear that the
addition of SO enormous weight as
this to the submerged part of the earth's
crust, outside the shore line, may well
produce strains too great to be resisted
1t must be remembered that the very
existence of precipitous shore line Gas
distinguished from one where the land
above water and the parts submerged
form one great slope) indicates the COM
parative weakness of the crust along
that coast. 1t has yielded on one side
to pressure thrusting it upward above
the sea-level, and on the other side to
the pressure of the water forcing it
down. 1t is true, the actual line OF
yielding may not coincide with the
existent shore line. For the action OF
~ go 49, ,, ma, Nano Senei any ihus'l
nave aitereu ohe position OF the coast
rom Z .naI whicn IL occupied when hrst
Iorlheu. put IL may De taken Tor granted
thae not iar from every precipitous
shore ilne iies a line OF Weakness where
.ne crust mas gwen way ID the past, and
may give way AGAIN IN TINS considora-
tlon undoubtedly we ma part OF the
explanation OF the observed iaet that
aiiliosl al !ne great regions OF supter-
raneah ACTIVITY on the earth lie neai the
sea,shore.
put WINE the changes OF atmospheric
anu oceanic pressure are potent factors
IN .ne Production OF earthquakes and
are Propaoiy IN the great number OF
cases their uifect occasion, 1t Is, OF
course 10 the subterranean regions
themselves that we must look for the
forces at WORK IN upheavlng the crust
OF the earth. Inc FORCES actlng from
tne outsiue are as the pun on the
trlggeri tne imprisoned gases and
vapors generated by internal heat are as
the powder by whose explosion the
missile Is eJected.