The Abbeville press and banner. [volume] (Abbeville, S.C.) 1869-1924, 1886-10-13
EARTH THROES.
ANOTHER EXPOSITION OF THE
CAUSES OF EARTHQUAKES.
Cyclopean Forces Acting From the
Eastern Atlantic-The Earth
Like a Peach Drying Up
Changes in the Atlantic.

Like q Peach Drying Up
Changes in the Atlantic.
Perhaps the best exposition of the
causes and characteristics of earthquakes
in general, and specially of our Atlantic
scaboard earthquakes, anywhere to be
! found is embodied in the address deliv-
cred by Sir William Dawson, President
of the British Association. This eminent
Canadian scientist, than whom no living
man is better fitted to expound tho for
nation and changes of the earth's crust,
; gave the probable history of the forma-
tion of the Atlantic Ocean and the con-
tinents which bound it. Assuming that
the earth's nucleus, or mass, is solid, not
withstanding the Elasticity of its under
crust, and that this sub-crust is not in q
state of dry igneous fusion, but in that
condition of aqueo-igneous or hydro
thermic fusion which arises from the ac-
tion of heat on mo st substances. Pro-
fessor Dawson argued that the interior
sub-crust is not homogeneous, but is
composed of two layers.-an upper layer
highly siliceous and of low specific
gravity and a lower layer highly
! charged with iron and igneous rocks.
1t is evident, therefore, that if this be the
double structure of the earth's under
crust, when fissures form in the upper
layer the material of the lower crust is
forced upward by the pressure of the less
supported portions Of the former.
This, of course, would give rise to
volcanic phenomena, which would be
explosive or quiet, rs determined by con-
tact with water. The contraction of the
earth's interior by cooling and by the
emission Of material from below the
over crust has caused this crust to bend
downward and sidewise. thus forming
great bends, folds and plications. These
great foldings, subsequently modified by
surface denudation, constitute our noun
tanges and plateaus.
Following this line of reasoning, Sir
William compares the earth to stone
fruit, such as plum or q peach, some
what dried up. 1T has," he says, "a
large and intensely hard stone and ker-
mel, thin pulp made up of two layers
an inner more dense and dark coIored,
and an outer less dense and lighter col
ored. These constitute the under crust.
On the outside it has q thin membrane
or over crust. In the process of drying
it has slightly shrunk so as to produce
ridges and hollows on the outer crust, and
this outer crust has cracked in some
places, allowing portions of the pulp to
ooze out"
Another remarkable fact emphasized
by Sir William Dawson is that one can
not look at any geological map of Amer
lea without perceiving that the Appa-
lachian ridges which intervene between
the Atlantic and the St. Lawrence Valley
have been driven bodily back by some
mighty force acting from the East, and
that they have resisted the pressure only
where (as in the Gulf of st. Lawrence
and the Catskill region of New York;
they have been protected by outlying
masses of very old rocks-as seen in the
Adirondack region and in Newfound-
land.
It is worthy of note that though later
in culture and civilization than some OF
the other continents, America is, in the
view of geologists, first born among the
continents " Here" said Agassiz, 'was
the first dry land lifted out of the waters,
here the first shore washed by the ocean
that enveloped all the earth beside; and
while Europe was represented only by
islands rising here and there above the
sea, America already stretched an un-
broken line of land from Nova Scotia to
the far West" In the case America, not
Europe, is to be regarded as the sold
World"
Bearing these data in mind, we can
easily see the force of Professor Daw-
sons conclusions. Coming to the pues-
tion of future changes in the Atlantic,
he says: "The question remains: Has
the Atlantic achieved its destiny and
finished its course, or are there other
changes in store for it in the future:
The earth's crust is now thicker and
stronger than ever before, and its great
ribs of crushed and folded rock are more
firm and rigid than in any previous pc
riod. On the other hand, it is known
that movements of elevation, along with
local depressions are in progress in the
Arctic regions, and great weight OF
new sediment is being deposited along
the borders of the Atlanti", especially
on its western side, and this is not i'm
I probably connected with the earthquake
shocks and slight movements OF depres-
sion which have occurred In North
America. 1t is possible that these
slow and secular movements may 60 on
uninterruptedly until considerable
changes are produced but it is quite as
likely that they may be retarded or re-
versed." He adds: 1T is possible, on
the other hand, that after the long period
of quiescence which has elapsed there
may be new settlement of the ocean
bed. accompanied with foldings of the
crust, especially on the western side OF
the Atlantic, and possibly with renewed
volcanic activity on its eastern margin.
In either case long time relatively to
our limited human chronology may in,
tervene before the occurrence of any
marked change. "-Me~ York Herald.