The sun. [volume] (New York [N.Y.]) 1833-1916, 1906-10-17
EARrH0UAKEs.
ReadJustufents Of weight ThAt Alter the
Flexible Earth Crust.

From the NiRstseRh Century.
The earth's crust is composed Of heterOgene-
Gus elements: but all possess one important
property. nexibility. though In varying de-
Rrees. Alike In very moderate elevations and
In lofty mountain chains the rocks are seen to
have been thrown into arches and trOughs and
even to have been crumpled and folded like
sheets OF paper or dislOcated or broken up by
the enormous strains and stresses they have
been subjected to. These are the strikes,
dips, synclinals and anticlinals. faults. folds,
upthrOws and downthrows Of biologists,
modest examples Of which can be seen any
where In cliffs and even In ~quarries and railway
cuttings.
or the conditions prevailing beneath the
crust we know far less. When pits are sunk
the temperature Increases at a progressive
rate with the depth. boiling springs are
encountered. some making their way to the
surface, red hot stones aud ash and molten
rock are violently extruded through vents,
but most significant OF all to the geologist isths
metamorDhism OF rocks. which must have
been melted at relatively moderate depths
but are now exposed on the surface In every
quarter of the globe. There Is thus the GER
tainty that the cooled surface is underlain
at some not altogether inaccessible depth
by rock In a molten state. both fluid and
pasty, through heat. Below this Is the In
tensely heated solid sphere, 10 which astron-
Omers assign the riCidity and density OF steel
and which is kept solid by compression Of the
external layers. Between the superheated
nucleus. kept solid by compression. and the
cool enveloping shell In which lies the com
pressing force. some intermediate condition
must exist. With lessening pressure nearer
the surface normal conditions must. prevail.
and rocks at their melting temperature must
be in the LIQUID state Of Stag from a smelling
furnace.
Our globe would therefore consist Of an
outer cooled heterogeneous and flexible crust,
with a temperature increasing downward and
point in a liquid state. which in turn overlie
the heated nucleus. kept solid by compression
and Of the rigidity OF steel.
III the crust were undisturbed, the molten
LAYER upon which il rests would be inactive;
but atmospheric. agencies. frost and rain,
are ceaselessly at work Transporting weight
from the hills and depositing II under the
sea, decreasing the pressure here and adding
TO 1t there; The rivers .debouch into the
deposited outside the influence Of the surf,
and the breakers. acting like a rasp along
the base OF the cliffs contribute their quota
coast. the material being carried out by the
waves TO swell the deposits forming parallel
to the shore within the littoral zone, Geology
reveals that these deposits may In time reach
thousands Of feet. In thickness. Slmulta-
neouely the removal Of weight by the breakers
the actual sea mar Gin Thus two parallel
lines are continually forming, the one OF
increasing pressure and the other OF decreas-
is the crust so flexible as to be. sensible
to such readiustments Of weight2 In n past
age when perhaps man was already among
from a glacial period. when vast ice caps
formed over the elevated regions. Under
Wales sank beneath the sea level, rising again
20 us existing height as the ice melted away.
IN hotter regions masses Of coral are forming
reefs and .atolls. rising In some cases from
water hundreds Of fathOms deep. The polypes
forming the coral can only live IN surf
near the surface. and unless subsistence had
continuously kept pace with deposition no
such masses could have been formed. Many
Of the great rivers empty into bays sheltered
which have been proved by borings to be
thousands OF feet thick. yet each foot has been
by the angle of bedding, the fauna. drifted
land debris and the sorting, action of the
waves, In all these cases the crust must
added material. and did II not similarly
give way under the additions Of weight along
woe hi'P be- s 1Gre ededy for fs'sn mii sad b Son sRosIt
no deeper than the disturbing motion Of the
waves, When the crust says out to sea the
the, pressure. The pressure acting on the
molten layer tends to squeeze IL. not seward
sbSrS x ths SI ! Tn Is az dfsep css but toward The
ready prepared by the breakers.
The effect OF steadily increasing lateral
pressure acting on a long and relatively weak
shore line Of heterogeneous materials must
be extremely complex. The molten matter
IL able 20 eat It's way upward like a corrosive
fluid melting the rocks IL successfully comes
in contact with. until it finds relief in pouring
out lava in streams of appalling magnitude.
This was the fate OF the seaboard of the north
east Atlantic in tertiary times. remains Of
these eruptions existing In the masses OF
basaltio trap rock in Antrim, the Hebrides,
Far0es, Iceland. Spitzbergen and Greenland.
But where the superincumbent strata are still
thick and massive, and especially where they
have been already arched into lines OF hills,
as, Judging by the watershed, must have
been the case along the Pacific coast OF Amer
lea, the molten matter would continually
and irresistibly force the crust upward, pro-
ducing a chain of mountains, volcanic or
otherwise. parallel to the coast. Slmulta-
neously, owing to the pressure beinE lateral,
the molten liquid would force itself along
existing cleavage planes and lines OF bedding
OF ANIMATED and stratinpd rocks, for ID must
not be overlooked that all sedimentary straits
upheaved above sea level are bent and strain ed,
dried and shrunk. and infltrated. everywhere
presenting lines OF fracture and partings, like
masonry on a Cyclopean scale. On these the
molten matter, capable OF dissolving as well
as penetrating, presses with ever increas-
ing lnsistence, gathering force perhaps for
years, until resistance suddenly yields and
the fiery LIQUID Ia injected with terrific dia-
ruptive force along the lines OF BEDDING Thus
the shocks OF earthquake which startle ciyili-
cation and destroy opulent cities are pro.
duced at uncertain intervals and without
warning. On the west coast Of America we
are witnessing this majestic action in FIJI
force to-day. for the mighty Pacific il slowly
deepening along Its eastern margin and rais-
ing its long shore line into colossal ridges
UhfOh nnyv Form aIDNOaf CON lp,,o., 49,