Evening star. [volume] (Washington, D.C.) 1854-1972, 1906-10-25
A BOUT EARTHQUAKES
READJUsTMENTs OF WEIGHT
THAT ALTER THE EARTH CRUST.
Theory of the Causes That Set the
World Trembling-Flexibility Of
the Mundane Surface.
From the Nineteenth Century.

From the Nineteenth Century.
The earth's crust is composed of heteroge-
neous elements; but all possess one i'm
portant property, fex:biity, though In vary
Ing degrees. Alike in very moderate eleva-
tons and In lofty mountain chains the
rocks are seen to have been thrown into
arches and troughs and even to have beer
crumpled and folded like sheets of paper or
dfslocated or broken up by the enormous
strains and stresses they have been SUBJ
jected to. These are the strikes, dips, syn
clinals and anticinals, faults, folds, up.
throws and doWnthrows of biologists, mod
est examples of which can be seen any
where in cliffs and even In uuarries and
railway cuttings
VI 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 en-
countered, some making their way to the
surface, red-hot stones and ash and molten
rocks are violently extruded through vents
but most significant of all to the geoloeist
Is the metamorphism of rocks, which must
nave been melted at relatively moderate
depths, but are now exposed on the surface
In every quarter of the globe. There is thus
the certainty that the cooled surface is I'M
derlaln at some not altogether inaccessible
depth by rock in a molten state both fluid
and pasty, through heat. Below this is the
intensely heated solid sphere, to which as
tronomers assign the rightly and density
of steel and which is kept solid by compress
sion of the external layers. Between the
superheated nucleus. kept solid by compress
sion, and the cool envelopng shell in which
lies the COMPRISING force, some intermed:-
ate condition must exist. With lessening
pressure nearer the surface normal condi-
tions must prevail, and rocks at their melt
ing temperature must be in the LIQUID state
OF Stag from smelling furnace.
The Temperature
Our globe would therefore consist of an
outer cooled heterogeneous and flexible
crust, with temperature increasing down.
ward and passing into rocks at and above
the melting point in liquid state, which in
turn overlie the heated nucleus, kept solid
by compression and of the rightly of steel.
If the crust were undisturbed, the molten
layer uponwhich 1t rests would be inactive:
but atmospheric agencies, frost and rain, are
ceaslessly at work transporting weight from
the hills and depositing it under the sea,
decreasing the pressure here and adding
to it there. The rivers debouch into the
sea charged with silt which is eventually
deposited outside the influence of the surf
and the breakers acting like a rasp along
the base of the cliffs contribute their quota
OF sediment, eroding and brea king up the
coast. the material being carried out by the
waves to swell the deposits forming parallel
to the shore within the littoral zone Cecil
ogy reveals that these deposits may in time
reach thousands of feet in thickness Stimuli
taneousiy the removal Of weight by the
breakers impafrs the resisting power of the
crust along the actual sea margin. Thus two
parallel lines are continually forming the
one OF increasing pressur eand the other of
decreasing resistance.
Is the crust SO flexible as to be sensible
to such readjustments of weight? In past
age when perhaps man was already
among its inhabitants the earth suffered in
places from a glacial period, when vast ice
caps formed over the elevated regions I'm
der one Of these Accommodations the whole of
Wales sank beneath the sea level, rising
again to its 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 polyps 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 from
coast currents and there form deltas which
have been proved by borings to be thou
sands of feet thick, yet each foot has been
formed in water few feet deep, as proved
by the angle of bedding, the fauna, drifted
land debris and the sorting action of the
waves. In all these cases the crust must
have 'Sagged under the increasing load of
added material, and did 1t not similarly
give way under the additions of weight
along the littoral zone every island and
continent would be surrounded for miles
by shoals no deeper than the disturbing
mOllOn OF the waves. w ucL Tic Cl SdSS
out to sea the column of water over it
deepens, augmenting the pressure. The
pressure acting on the molten layer tends
to squeeze 1t, not seward where the water
is deeper, but toward the shore where
line of least resistance IS already prepared
by the breakers.
Increasing Pressure.
The effect Of steadily increasing lateral
pressure acting on q lor- and relatively
weak shore line of heterogeneous materials
must be extremely complex The molten
matter is able to eat its way upward like
a corrosive fluid melting the rocks 1t sue
cessively comes in contact with, until it
finds relief in pouring out lava In streams
fappalling magnitude. This was the
fate of the seaboard of the northeast At
lantic in tertiary times, remains Of these
eruptions existing in the masses of basaltic
trap rock in Antrim, the Hebrides, Faroes,
Iceland, Spitzbergen and Greenland. But
where the superintendent strata are still
thick and massive. and especially where
they have been already arched into lines Of